Patent Publication Number: US-2013231931-A1

Title: System, method, and apparatus for generating, customizing, distributing, and presenting an interactive audio publication

Description:
This application is a divisional of U.S. application Ser. No. 12/726,230, filed on Mar. 17, 2010, now allowed, which claims the benefit of U.S. Provisional Application No. 61/160,787, filed on Mar. 17, 2009, both of which are incorporated by reference herein in their entireties. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the generation, customization, distribution, and presentation of an interactive audio publication wherein interactive audio content is generated from text-based and speech-based content. 
     2. Background Art 
     Individuals are increasingly consuming news on-the-go in many forms. The explosive growth in mobile computing devices such as smart phones, portable media players (PMPs), and netbooks has fueled demand for news content that can be accessed anywhere and anytime. Digital versions of newspapers and news magazines can be downloaded for visual presentation on mobile electronic devices, and daily audio podcasts cover a wide variety of topics. 
     While visually-oriented online news content offerings are vast, varied, and dynamic, they do not provide busy multitasking individuals with convenient news consumption opportunities. Online newspapers and news magazines, for example, provide coverage on a variety of topics in multiple levels of detail, but due to the visual and “page-based” nature of these media, they cannot be utilized fully or effectively while driving, exercising, or otherwise multitasking. 
     Audio news content ranges from traditional broadcast radio news programs to prerecorded audio podcasts and live streaming audio feeds that can be presented on mobile computing devices. Audio news content is especially well-suited for consumption while multitasking, but it lacks sufficient interactivity. For example, with broadcast radio, an individual&#39;s interactivity is limited to changing the channel. While podcasts and Internet streaming radio offer slightly more interactivity, individuals are still limited to the standard navigation functions (e.g., next/previous track, seek forward/backward, etc.) provided by a media player. Furthermore, navigating an audio podcast using a media player&#39;s controls is cumbersome and even dangerous when performing other activities, such as driving. 
     Recently, the navigability and usability of podcasts has improved. For example, Apple, Inc. created “enhanced podcasts” which combine traditional audio podcasts with embedded chapter information, enabling intra-podcast navigation. Enhanced podcasts also allow visual content to be synchronized for display during podcast presentation. Similarly, the MP3 standard offers “ID3v2 Chapter” tags to enable both intra-audio file navigation and synchronized visual content presentation, although the tags are not widely supported by media players. Despite these enabling technologies, a user must still fumble with media player controls and menus to navigate through enhanced audio content. Furthermore, a standard method for segmenting audio news content does not exist. 
     Clearly, there is a need for an interactive audio publication system that combines the dynamic qualities of visually-oriented news media with the presentation flexibility of audio news media. 
     There is also a need for alternative news consumption techniques for the elderly and for individuals with impaired vision. While audio versions of newspapers are available for the visually impaired (e.g., the National Federation of the Blind provides telephone access to audio versions of newspapers created using text-to-speech technology), they support only limited interactivity and have a cumbersome interface that uses a telephone keypad. 
     Companies such as BuzzVoice and Stitcher currently allow users to customize audio news content for playback via the Web or a portable media player. BuzzVoice uses computerized text-to-speech (TTS) technology to convert text-based content into audio podcasts, while Stitcher allows users to create a playlist of selected audio podcasts that is then streamed to their media player. Both companies focus on customized audio news content, but neither provides a combination of customization and audio content interactivity. 
     SUMMARY OF THE INVENTION 
     This Summary is provided to introduce a selection of concepts in a simplified form. The concepts are further described below in the Detailed Description section. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. 
     Methods, systems, and computer program products that enable interactive audio publications and further embodiments are described herein. Systems, methods, and apparatuses are described herein for generating, customizing, distributing, and presenting an interactive audio publication. 
     In one aspect, an interactive audio publication system includes a creation system, a customization &amp; distribution system, a presentation system, and a subscriber portal. The interactive audio publication system provides solutions for generating, customizing, distributing, and interacting with interactive audio content. 
     The creation system provides functionality to enable interactive audio publications to be generated for presentation on a presentation system. Text-based and plain speech-based content (e.g., podcasts, radio programs, etc.) are enabled to be transformed into interactive “audio content items.” Human voice talent and/or computerized text-to-speech may be employed to convert text-based content to speech. Additionally, navigable audio publications are enabled to be generated by organizing the audio content items into sections. Generated audio publications may be archived and retrieved on-demand using the audio publication Archiving &amp; Retrieval module described herein. 
     The customization &amp; distribution system generates one or more custom audio publications based on one or more custom audio publication templates generated by a subscriber. The customization &amp; distribution system may handle the distribution of prepared custom audio publications to subscribers for presentation on a presentation system. Custom audio publications may be generated using static assignment rules and/or dynamic search-based criteria. In addition, techniques are described for optionally selecting and scheduling audio and/or visual advertisements for playback and/or display during presentation of an audio publication. Techniques are also described for distributing both new and updated audio publications, with the ability to stream audio publications on-demand. 
     The subscriber portal enables subscribers to manage their account and profile settings, to configure one or more “custom audio publication templates,” to access and share audio content items, and to configure presentation system runtime preferences. Techniques are presented for generating one or more custom audio publication templates that are utilized by the customization &amp; distribution system to generate one or more custom audio publications for each subscriber. In one example, the subscriber portal may be implemented as a Web site with an integrated presentation system. 
     The presentation system includes a presentation manager and a presentation device. The presentation manager prepares received interactive audio publications for presentation on a particular presentation device. The presentation device presents interactive audio publications dynamically using special metadata that describes the overall structure of the audio publication and the internal structure of each constituent audio content item. 
     During presentation, subscribers may interact with the presentation device using voice commands and/or an intuitive button interface. The presentation device monitors a subscriber&#39;s progress through each audio publication and provides real-time status reporting upon request. Additionally, this aggregate audio publication “state” is shared periodically with the customization &amp; distribution system, enabling novel audio publication customization capabilities, targeted advertisement selection, and the ability to synchronize a plurality of presentation systems. 
     Additional features and advantages of the invention, as well as the structure and operation of various embodiments of the invention, are described in detail below with reference to the accompanying drawings. It is noted that the invention is not limited to the specific embodiments described herein. Such embodiments are presented herein for illustrative purposes only. Additional embodiments will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES 
       The accompanying drawings, which are incorporated herein and form a part of the specification, illustrate the present invention and, together with the description, further serve to explain the principles of the invention and to enable a person skilled in the relevant art(s) to make and use the invention. 
         FIG. 1  shows a high-level block diagram of the interactive audio publication system, according to an example embodiment. 
         FIG. 2A  shows a block diagram depicting a system for audio content item generation from text-based content items, according to an example embodiment. 
         FIG. 2B  shows a block diagram depicting a system for audio content item generation from speech-based content items, according to an example embodiment. 
         FIG. 3A  shows a block diagram depicting a system for managed audio publication generation, according to an example embodiment. 
         FIG. 3B  shows a block diagram depicting a system for automated ad hoc audio publication generation, according to an example embodiment. 
         FIG. 4  shows a block diagram depicting an audio publication archiving and retrieval system, according to an example embodiment. 
         FIG. 5A  shows a block diagram depicting an audio publication customization module, according to an example embodiment. 
         FIG. 5B  shows a block diagram depicting a custom audio publication creation module, according to an example embodiment. 
         FIG. 5C  shows a block diagram depicting a keyword search-based audio content item selection module, according to an example embodiment. 
         FIG. 5D  shows a block diagram depicting a relevance-based audio content item selection module, according to an example embodiment. 
         FIG. 6A  shows a block diagram that depicts a system for advertisement selection and scheduling in which advertisements are selected and scheduled prior to audio publication delivery and presentation, according to an example embodiment. 
         FIG. 6B  shows a block diagram that depicts a system for advertisement selection and scheduling in which advertisements are selected and scheduled as audio content items are streamed on-demand, according to an example embodiment. 
         FIG. 7A  shows a block diagram depicting an audio publication distribution module, according to an example embodiment. 
         FIG. 7B  shows a block diagram depicting an audio publication delivery module, according to an example embodiment. 
         FIG. 8  shows a block diagram depicting a subscriber portal, according to an example embodiment. 
         FIG. 9  shows a block diagram of a presentation manager, according to an example embodiment. 
         FIG. 10  shows a block diagram of a presentation device, according to an example embodiment. 
         FIG. 11  shows a block diagram depicting a presentation device speech recognition module, according to an example embodiment. 
         FIG. 12  shows a block diagram depicting an example presentation device, according to an embodiment. 
         FIG. 13  shows an illustration of an exemplary plug-in presentation device, according to an embodiment. 
         FIGS. 14A and 14B  show a flowchart depicting a presentation device main process, according to an example embodiment. 
         FIG. 15  shows a flowchart depicting an “Initialization” process, according to an example embodiment. 
         FIGS. 16A-16D  show a flowchart depicting a “Handle Command” process, according to an example embodiment. 
         FIG. 17  shows a flowchart depicting a “Handle Title Mode” process, according to an example embodiment. 
         FIG. 18  shows a flowchart depicting a “Handle Summary Mode” process, according to an example embodiment. 
         FIG. 19  shows a flowchart depicting a “Handle Played Audio Content Item” process, according to an example embodiment. 
         FIG. 20  shows a flowchart for presenting an interactive audio publication, according to an example embodiment. 
         FIG. 21  shows a block diagram of an example computer that may be used to implement embodiments of the present invention, according to an example embodiment. 
     
    
    
     The features and advantages of the present invention will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, in which like reference characters identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The drawing in which an element first appears is indicated by the leftmost digit(s) in the corresponding reference number. 
     DETAILED DESCRIPTION 
     The present specification discloses one or more embodiments that incorporate the features of the invention. The disclosed embodiment(s) merely exemplify the invention. The scope of the invention is not limited to the disclosed embodiment(s). The invention is defined by the claims appended hereto. 
     References in the specification to “one embodiment,” “an embodiment,” “an example embodiment,” etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the relevant art(s) to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. 
     Embodiments of an interactive audio publication system are described herein. Such embodiments enable users to navigate quickly and easily through audio publications, scan story title and article headlines rapidly, and adjust the desired levels of presentation detail on-the-fly, without requiring any distracting physical intervention. Furthermore, users are enabled to customize an interactive audio publication to their own unique news source and topic preferences. For instance,  FIG. 1  shows a block diagram of an interactive audio publication system  100 , according to an example embodiment. As shown in  FIG. 1 , interactive audio publication system  100  includes a creation system  102 , a customization &amp; distribution system  110 , a subscriber portal  124 , and a presentation system  136 , which are subsystems of system  100 . System  100  is described as follows. 
     In embodiments, interactive audio publication system  100  may feature numerous implementation and deployment options. Interactive audio publication system  100  may be implemented in hardware, software, firmware, or any combination thereof. For instance, in an example embodiment, creation system  102 , customization &amp; distribution system  110 , and subscriber portal  124  may each include one or more software applications that are deployed on a single computer or on a plurality of computers with access to various enterprise resources (e.g., databases  118 ,  120 , and  122 , software modules, etc.). In an embodiment, systems  102  and  110  and portal  124  may be deployed on a single computer. In an embodiment, systems  102  and  110  and portal  124  may be co-located or alternatively distributed across one or more geographic areas. Systems  102  and  110  and portal  124 , and any enterprise resources utilized by systems  102  and  110  and/or portal  124  may be connected via one or more local area networks (LANs), wide area networks (WANs), virtual private networks (VPNs), and/or interconnect systems. Access rights to various software systems, system modules, and enterprise resources utilized by systems  102  and  110  and/or portal  124  may be configured for each entity involved in the audio publication generation, customization, and distribution processes described herein. 
     Subscriber portal  124  may be implemented in various ways. For instance, in an embodiment, subscriber portal  124  may be deployed as a Web site with an integrated presentation system (e.g., presentation system  134  shown in  FIG. 1 ). In another embodiment, subscriber portal  124  may be implemented as a module within presentation system  136  (e.g., within a presentation device  140  shown included in presentation system  136  in  FIG. 1 ). In further embodiments, subscriber portal  124  may be implemented in other ways. 
     Presentation system  136  may be implemented using one or more computing resources configured in various ways. For example, as shown in  FIG. 1 , presentation system  136  includes a presentation manager  138 , a presentation device  140 , and one or more third-party support modules  142 , which are described in detail further below. In an embodiment, presentation device  140  may be implemented as a standalone hardware device (e.g., a laptop computer, a notebook computer, a smart phone, a handheld computer, a custom hardware device, etc.), an attachable device (e.g., a plug-in device), a software application targeted for a PMP, a smart phone, or other computing platform, or other suitable device mentioned elsewhere herein or otherwise known. Presentation manager  138  may be integrated with presentation device  140 , or may alternatively be deployed as a separate application that executes on the same computing resources used by presentation device  140  or on different computing resources. In an embodiment, presentation system  136  may be embedded in a larger system, such as an in-vehicle entertainment system, etc. In an embodiment, presentation manager  138 , presentation device  140 , and/or third-party support modules  142  may be connected together using standard or proprietary data communications and/or networking technologies including but not limited to USB (universal serial bus), serial, I2C, Ethernet, and the like. 
     The elements of interactive audio publication system  100  shown in  FIG. 1  are described in the following subsections with respect to  FIGS. 2A-13 . It is noted that in embodiments, same or similarly named features shown in and referenced with regard to  FIGS. 1-13 , including databases, modules, engines, etc., may be the same feature regardless of whether the same or different reference numerals are used in different figures. For example, an audio content items database having different reference numerals in different figures may be the same audio content item database, in an embodiment. In other embodiments, one or more of the same or similarly named features referenced with regard to  FIGS. 1-13  may be separate implementations of the one or more same or similarly named features. 
     In the context of this document, a “content item” is a fundamental unit of information, based on either speech or written text (e.g., in electronic form, such as online text). A content item that is based on speech, including but not limited to podcasts, radio programs, and other audio files that include speech content, is referred to herein as a “speech-based content item.” A content item that is based on written text, including but not limited to newspaper articles, magazine articles, RSS (Really Simple Syndication) text feeds, and the like, is referred to herein as a “text-based content item.” 
     In the context of this document, a “content provider” is an entity that provides one or more text-based and/or speech-based content items. 
     In the context of this document, a “publisher” is an entity that creates audio publications and “audio content items” from one or more text-based and/or speech-based content items provided by a content provider. 
     In the context of this document, an “audio content item” is generated from either a text-based or speech-based content item. An audio content item may include audio data containing a spoken representation of the text-based or speech-based content item and metadata that describes the structure of the audio data. In some embodiments, it may be useful to package the audio data in one or more audio files and to encode the audio data according to a standard or proprietary audio encoding technique (e.g., MP3, AAC, etc.). The audio content item metadata may be represented using XML, or an alternative machine-parseable format. 
     Audio content items may be logically divided into three consecutive non-overlapping “audio segments” called a title segment, a summary segment, and a story body segment. The title segment is an audio segment that announces the audio content item&#39;s title, and optionally, the source content item&#39;s author and/or date. The summary segment may include one or more of the audio content item&#39;s introductory paragraphs. The summary segment may be generated directly from the source content item or alternatively from a content item that is provided separately. In an embodiment, the title segment may be relatively short when compared to the summary segment. In an embodiment, a default summary segment length may be specified in the presentation system runtime preferences (see section D.4). The story body segment includes the remainder of the audio content item (e.g., other than the title segment and summary segment). In some embodiments, it may be advantageous to store the title, summary, and story body segments in separate audio files called “audio content item fragments.” 
     As shown in  FIG. 1 , presentation system  136  includes a presentation manager  138 , a presentation device  140 , and one or more third-party support modules  142 . Audio content item metadata enables presentation device  140  to perform navigation and interaction functions described in section D. The audio content item metadata may include a plurality of word-based boundary markers (e.g., one or more words that designate the beginning and/or end of each of an audio content item&#39;s title, summary, and story body segments), a plurality of time-based boundary markers (e.g., an audio recording timestamp referenced from the beginning of the audio recording, etc.), and/or a plurality of references to one or more files, including but not limited to audio content item fragments, visual content items, and advertisements. For example, time-based boundary markers may be used to designate the location of each word, sentence, and paragraph contained in an audio content item, as measured from the beginning of the audio content item&#39;s audio recording. Additionally, time-based and/or word-based boundary markers may be used to define a presentation schedule (i.e., scheduling details) for one or more “visual content items,” and/or “advertisements,” as defined below. Audio content item metadata may also include the text of a corresponding text-based content item or a transcript of a corresponding speech-based content item, so as to enable various functionalities as described herein (e.g., audio content item searching). In some embodiments, the audio content item metadata may be embedded within the audio data (e.g., using an ID3 tag), or packaged separately. 
     In the context of this document, a “visual content item” is a file that contains data for visual display. Examples of visual content items include image files (e.g., JPEG, PNG, etc.) and video files (e.g., MPEG, AVI, Flash, etc.). One or more visual content items may be associated with an audio content item and scheduled for display during presentation of the audio content item. Visual content item scheduling details may be stored in the associated audio content item metadata, for example. 
     In the context of this document, an “advertisement” is an object that may include one or more files containing audio data (e.g., one or more audio files) and/or visual data (e.g., one or more image files, video files, textual information, etc.) that may be optionally distributed with an audio publication and displayed during presentation of an audio content item. 
     In the context of this document, a “speech prompt” is a spoken representation of an alert, announcement, or other informational fragment (e.g., the audio publication name, a navigation option, a personalized greeting, etc.) that may be played when an audio publication is presented. 
     In the context of this document, an “interactive audio publication,” also referred to as an “audio publication,” includes a collection of one or more audio content items that are organized into one or more sections (e.g., Technology, Entertainment, Sports Podcasts, etc.) such that each section contains at least one audio content item. An audio publication may further include metadata that defines a complete audio publication structure. An audio publication may optionally further include one or more visual content items, one or more advertisements, and/or one or more speech prompts. Collectively, these constituent audio publication entities are referred to as “audio publication components.” 
     An audio publication&#39;s structure is defined by its metadata. Audio publication metadata defines an ordered list of sections contained within an audio publication and provides association details that map one or more audio content items to one or more sections. Additionally, audio publication metadata may contain advertisement scheduling details (e.g., see section B.3), and speech prompt presentation rules that specify when one or more prerecorded speech prompts are to be played during presentation of an audio publication. Optionally, the audio content item metadata for each constituent audio content item may be embedded within the audio publication metadata. In one embodiment, audio publication metadata is represented using XML, or an alternative machine-parseable format. 
     In the context of this document, a “subscriber” is an entity that subscribes to one or more audio publications, optionally generates one or more new custom audio publications, and consumes audio publication content via the presentation system embodiments described herein. The term “user” may be used herein to describe an entity that consumes audio publication content via the presentation system embodiments described herein (e.g., is not necessarily a subscriber). It is noted that in some cases where a “subscriber” is referred to herein as performing an act (e.g., consuming content, providing a command, etc.), the “subscriber” may alternatively be a “user.” For instance, a “user” may use a presentation device to consume audio publication content without actually subscribing to the audio publication content (e.g., the user may have borrowed a presentation device from a subscriber, etc.). 
     In the context of this document, a “custom audio publication template” is a collection of subscriber-specified rules and preferences that are used to generate a “custom audio publication.” Several example techniques for customizing audio publications are described in section B.2. 
     A. Example Creation System Embodiments 
     As shown in  FIG. 1 , creation system  102  includes an audio content item creation module  104 , an audio publication creation module  106 , and an audio publication archiving &amp; retrieval module  108 . 
     Creation system  102  is configured to generate audio content items and audio publications  118 . There is flexibility regarding the order in which audio content items and audio publications are generated. For example, audio content item generation may occur after the assembly of an encompassing audio publication, in which case audio content item placeholders may be substituted for audio content items within the generated audio publication. Additionally, audio content item generation may occur in a plurality of “assembly stages,” such that one or more portions of an audio content item are generated prior to assembly of an encompassing audio publication, and remaining portions are generated later (e.g., immediately prior to presentation by presentation system  136 ). In an embodiment, portions of creation system  102  may be performed by presentation system  136  (e.g., audio content item generation). 
     A.1. Example Audio Content Item Generation Embodiments 
     Audio content item creation module  104  is configured to generate audio content items. Audio content item creation module  104  may be configured in various ways. For instance,  FIGS. 2A and 2B  show block diagrams of audio content item creation module  104 , according to example embodiments.  FIG. 2A  depicts a system  200  for generating an audio content item  242  from a text-based content item  204 , and  FIG. 2B  illustrates a system  250  for generating an audio content item  294  from a speech-based content item  254 .  FIGS. 2A and 2B  illustrate exemplary techniques by which audio content items are generated prior to generation of an encompassing audio publication. It is understood that  FIGS. 2A and 2B  are presented by way of example to assist in understanding the processes involved in generating audio content items, and modifications may be made to these examples to realize further embodiments. 
     As shown in  FIG. 2A , system  200  includes a text-to-speech module  206 , an ID3 tag updating module  216 , a word/sentence/paragraph segmentation module  220 , a computer ASR (automatic speech recognition) system  222 , an audio content item segmentation module  226 , a visual content item selection &amp; scheduling module  230 , an audio content item metadata creation module  236 , and a combiner  240 . These elements of system  200  are described as follows. 
     Referring to  FIG. 2A , a text-based content item  204  is supplied by a content provider  202 . Ancillary data such as the text-based content item publisher, author, date/time, unique identifier, etc., may also be provided with text-based content item  204 . Text-based content item  204  is converted to speech by text-to-speech module  206 . As indicated in  FIG. 2A , text-to-speech module  206  may include one or more of human voice talent  208 , computerized text-to-speech (TTS)  210  (e.g., a text-to-speech application), or a combination of both to perform text-to-speech conversion. In addition, prerecorded sound bites  212  may be inserted into the generated audio at desired locations by text-to-speech module  206 . For example, sound bites  212  may be utilized for spoken quotations and/or for specific text segments within text-based content item  204 . Text-to-speech module  206  generates speech-based audio data  214 , which may optionally be encoded (e.g., as digital audio data) and stored in one or more standard audio files (e.g., MP3, AAC, etc.); MP3-encoded audio data is assumed in this document for purposes of illustration. 
     ID3 tag updating module  216  receives speech-based audio data  214 . In an embodiment, ID3 tag updating module  216  updates standard MP3 ID3 tags (i.e., genre, artist, album, song title) (or similar tags defined by an alternative audio format) using the optionally provided content item ancillary data. For example, Table 1 illustrates an example of ID3 tag mapping that may be used for audio content items generated from standard newspaper articles: 
                     TABLE 1                  Example of standard ID3 tag mapping for an audio content       item generated from a newspaper article.                             ID3 Tag   Information Stored                       Genre   Newspaper Publisher           Artist   Text-based Content Item Author           Album   Section (e.g., “Editorials”)           Song Title   Headline                        
ID3 tag updating module  216  generates encoded and ID3-tagged audio data  218 .
 
     Speech-based audio data  214  is received and processed by segmentation module  220  to locate individual word, sentence, and paragraph boundaries contained therein. Word, sentence, and paragraph segmentation may be performed by segmentation module  220  either manually or automatically. For example, automatic speech recognition (ASR) system  222  may be used to locate the word, sentence, and paragraph boundaries through a process called forced alignment. Additionally, if a TTS (text-to-speech) engine  210  is used to generate speech-based audio data  214  in module  206 , the segmentation information may be obtained from TTS engine  210  during the conversion process. 
     Segmentation module  220  generates a list  224  of timestamps corresponding to the time-based boundaries for each word, sentence, and paragraph contained in speech-based audio data  214 . Audio content item segmentation module  226  receives and uses timestamp list  224  and the text of text-based content item  204  to divide speech-based audio data  214  logically into non-overlapping title, summary, and story body segments. Audio content item segmentation module  226  generates a list  228  of timestamps denoting a start time and end time of each audio content item segment. Together, word/sentence/paragraph timestamp list  224  and audio content item segment timestamp list  228  constitute a core audio content item structure and are used by audio content item metadata creation module  236  to generate audio content item metadata  238 . As described elsewhere herein, audio content item metadata  238  may include boundary markers (e.g., time-based boundaries, etc.) for the corresponding audio content item, scheduling details for one or more visual content items and/or one or more advertisements associated with the audio content item, the text of the corresponding text-based content item, etc. 
     Visual content item selection and scheduling module  230  receives timestamp list  224  and one or more visual content items  232 , which may be selected and scheduled for display during presentation of audio content item  242 . Optionally, one or more visual content items  232  may be provided with text-based content item  204 . Visual content items  232  may include photographs, images, artwork, video, and/or other visual-oriented media that can be sequenced for display using timestamp list  224  output from segmentation module  220 . 
     Visual content item selection &amp; scheduling module  230  provides several options for sequencing visual content items  232 . A visual content item&#39;s initial display time may be associated with a particular word instance within an audio content item, or the display duration may be mapped to a particular text segment. Additionally or alternatively, visual content items  232  may be sequenced automatically such that selected visual content items are distributed uniformly throughout an audio content item. 
     In one embodiment, a publisher may schedule visual content items  232  using an application included in module  230 . For instance, the application may provide a graphical user interface (GUI) enabling the publisher to schedule visual content items  232  with a graphical timeline or by highlighting specific text segments within text-based content item  204 . Visual content selection &amp; scheduling module  230  generates visual content item scheduling details  234  (e.g., scheduling information), which include the selected visual content items and a set of timestamps (or word-based boundary markers) designating the presentation start and end times for each selected visual content item. Visual content item scheduling details  234  are received by audio content item metadata creation module  236 . 
     Audio content item metadata creation module  236  automatically generates audio content item metadata  238  using the full text and any ancillary data from text-based content item  204 , list  224  of timestamps corresponding to the word/sentence/paragraph boundaries, list  228  of timestamps corresponding to the audio content item segment boundaries, and visual content item scheduling details  234 . In one embodiment, audio content item metadata  238  is represented using XML with a clearly defined schema. Optionally, audio content item metadata  238  may be combined with encoded and ID3-tagged audio data  218  by a combiner  240 , such as by embedding metadata  238  in an unused ID3 tag. Together, encoded and ID3-tagged audio data  218  and audio content item metadata  238  constitute a newly-generated audio content item  242 . 
     Whereas  FIG. 2A  depicts system  200 , which is configured to generate audio content items from text-based content items,  FIG. 2B  illustrates system  250 , which is configured to generate audio content items from speech-based content items such as podcasts, recorded radio broadcasts, and the like. Speech-based content items may be provided in various forms (e.g., as digital audio data) and formats, such as standard audio files (e.g., MP3, AAC, etc.). MP3 audio files are referred to in this document for ease of illustration. As shown in  FIG. 2B , system  250  includes an ID3 tag updating module  258 , a speech-to-text module  262 , a computer ASR system  264 , a transcript selector  268 , a word/sentence/paragraph segmentation module  272 , an audio content item segmentation module  278 , a visual content item scheduling module  284 , an audio content item metadata creation module  288 , and a combiner  292 . These elements of system  250  are described as follows. 
     Referring to  FIG. 2B , a speech-based content item  254  is supplied by a content provider  252 . Ancillary data such as the speech-based content item publisher, author, date/time, unique identifier, etc., may also be provided with speech-based content item  254 . If ancillary data is provided, ID3 updating module  258  may use the ancillary data to update the ID3 (or equivalent) tags (i.e., genre, artist, album, song title) of speech-based content item  254 . The output of ID3 updating module  258  is an encoded (e.g., MP3 encoded) and ID3-tagged audio file  260 . 
     Optionally, a transcript  256  of speech-based content item  254  may be provided. If transcript  256  is not provided, then speech-based content item  254  may be converted to text by speech-to-text module  262 , either manually or by an automatic speech recognition (ASR) system  264 . Speech-to-text module  262  generates a decoded transcript  266  of speech-based content item  254 . Selector  268  selects either transcript  256  (if provided with speech-based content item  254 ) or decoded transcript  266  if transcript  256  is not available. Segmentation module  272  receives and analyzes speech-based content item  254  and selected transcript  270  to determine word, sentence, and paragraph time-based boundaries in speech based content item  254 . For instance, in an embodiment, ASR system  264  may be used by segmentation module  272  to perform the boundary determinations. If ASR system  264  is used to perform the segmentation and transcript  256  is not provided, punctuation and grammar rules/heuristics  274  may be used by segmentation module  272  to identify word, sentence, and paragraph boundaries automatically. Segmentation module  272  generates a list  276  of timestamps corresponding to the time-based boundaries for each word, sentence, and paragraph contained in speech based content item  254 . 
     As shown in  FIG. 2B , audio content item segmentation module  278  receives timestamp list  276 . Module  278  uses the extracted word, sentence, and paragraphs boundaries indicated in list  276  and selected transcript  270  to divide speech-based content item  254  into the title, summary, and story body segments. Audio content item segmentation module  278  generates a list  280  of timestamps denoting the start and end time of each audio content item segment. Together, timestamp lists  276  and  280  constitute a core audio content item structure and are received and used by audio content item metadata creation module  288  to generate audio content item metadata  290 . Audio content item metadata  290  may include any of the audio content item metadata components (i.e., boundary markers, scheduling details, transcripts, etc.) described elsewhere herein. 
     One or more visual content items  282  may be optionally scheduled for display during presentation of audio content item  294  by visual content item selection &amp; scheduling module  284 . Using timestamp list  276  generated by segmentation module  272 , visual content selection &amp; scheduling module  284  generates visual content item scheduling details  286 , which include the selected visual content items and a set of timestamps designating the presentation start and end times for each selected visual content item. In an embodiment, timestamp lists  276  and  280  and visual content item scheduling details  286  may be used by audio content item metadata creation module  288  to generate audio content item metadata  290  for audio content item  294 . 
     Optionally, audio content item metadata  290  may be combined with encoded and ID3-tagged audio file  260  by combiner  292  (e.g., by embedding metadata  290  in an unused ID3 tag). Together, encoded and ID3-tagged audio file  260  and audio content item metadata  290  form a newly-created audio content item  294 . 
     A.2. Example Audio Publication Generation Embodiments 
     Referring back to interactive audio publication system  100  of  FIG. 1 , audio content items that are generated by audio content item creation module  104  are contained in one or more audio publications. Accordingly, audio publication creation module  106  may be configured for both manual and automated audio publication creation.  FIGS. 3A and 3B  depict block diagrams of audio publication creation module  106 , according to example embodiments.  FIG. 3A  depicts a system  300  in which a publisher  302  manages the generation of an audio publication  328 , and  FIG. 3B  illustrates a system  350  in which an ad hoc audio publication  368  is generated automatically by a software publisher. In both systems  300  and  350 , audio publications are generated by grouping and organizing one or more audio content items into one or more audio publication sections. Systems  300  and  350  are described as follows. 
     A.3. Example Managed Audio Publication Generation Embodiments 
     As shown in  FIG. 3A , system  300  includes an audio publication section layout editing module  304 , an audio content item assignment module  312 , an audio content item assignment details extraction module  318 , an audio publication assembly module  324 , and a notification module  330 . These elements of system  300  are described as follows. 
     Referring to  FIG. 3A , an audio publication publisher  302  may use audio publication section layout editing module  304  to generate and/or modify an audio publication section layout  306 . An audio publication section layout  306  includes an ordered list of one or more audio publication sections (e.g., a “Front Page” section, a “Business” section, etc.), and optionally, one or more selected speech prompts  322 . Optionally, a default audio publication section layout may be provided by section layout template  308 . Section layout template  308  may be edited within audio publication section layout editing module  304 . For example, publisher  302  may add, delete, rename, and/or reorder sections to generate audio publication section layout  306 . Additionally, publisher  302  may select and associate one or more speech prompts  322  with one or more sections indicated in section layout  306 . For example, speech prompts may be used during audio publication presentation to announce a selected audio publication section name or the name of the audio publication. Generated audio publication section layout  306  may be saved as a template  308  for future use. 
     One or more audio content items  310 , which may be provided via a database or other source, may be selected by publisher  302  and added to one or more audio publication sections indicated by audio publication section layout  306 . Within an audio publication, a single audio content item may be associated with one or more audio publication sections. For example, an audio content item might be associated with both a “Front Page” and a “Business” section. 
     Audio content item assignment details  314  and/or  316  indicate a mapping of audio content items  310  to one or more audio publication sections defined in audio publication section layout  306  (i.e., the section(s) to which each audio content item is to be added, etc.). Audio content item assignment details  314  may be provided separately by publisher  302 . Alternatively, audio content item assignment details  316  may be extracted automatically from selected audio content items  310  by audio content item assignment details extraction module  318 . As shown in  FIG. 3A , audio content item assignment module  312  receives audio publication section layout  306 , and audio content item assignment details  314  and/or audio content item assignment details  316 . Using audio content item assignment details  314  and/or  316 , audio content item assignment module  312  maps selected audio content items  310  to one or more audio publication sections defined in audio publication section layout  306 . Audio content item assignment details  314  and/or  316  may also define a sequential ordering of audio content items within each audio publication section, as determined by publisher  302 . In one embodiment, audio content item assignment module  312  may be automated (e.g., may include automated processes). As shown in  FIG. 3A , audio content item assignment module  312  generates audio content item sectional assignments  320 . 
     Audio publication assembly module  324  receives audio publication section layout  306  and audio content item sectional assignments  320 . Module  324  generates audio publication metadata and assembles an audio publication  328  by including all referenced audio content items  310 , visual content items  326 , and speech prompts  322  in assembled audio publication  328 . In an embodiment, audio publication metadata is generated by module  324  and is included in audio publication  328 . For example, the audio publication metadata may be a machine-parseable representation of an audio publication structure and may contain the names and ordering of all constituent sections, the audio content item sectional assignments, the ordering of audio content items within each section, and one or more speech prompt presentation rules. In one embodiment, the audio publication metadata may be represented using XML. 
     In an embodiment, the audio content item metadata for constituent audio content items  310  may be embedded directly in the audio publication metadata generated by audio publication assembly module  324 . Alternatively, the constituent audio content item metadata may be referenced indirectly from within the generated audio publication metadata. 
     In an embodiment, notification module  330  may issue a notification  332  whenever a new or updated audio publication is assembled by audio publication assembly module  324 . Notification  332  may be received by customization &amp; distribution system  110 , for example, to trigger the execution of customization processes enabled thereby. 
     A.4. Example Automated Audio Publication Generation Embodiments 
     Whereas  FIG. 3A  depicts system  300 , in which audio publication generation is managed by a publisher  302 ,  FIG. 3B  depicts system  350 , in which one or more ad hoc audio publications  368  may be generated automatically by a software-based publisher (e.g., an automated publisher that generates ad hoc audio publications  368  according to an automated process). An ad hoc audio publication  368  contains one or more audio content items  352  from a selected “content source” (e.g., podcasts, RSS feeds, blogs, and the like) that are organized into a standard set of one or more sections (e.g., World News, Entertainment, etc.). 
     As shown in  FIG. 3B , system  350  includes an audio content item metadata extraction module  354 , an audio content item analysis module  358 , an ad hoc audio publication creation module  362 , and a notification module  370 . These elements of system  350  are described as follows. 
     Referring to  FIG. 3B , one or more audio content items  352  are received by automated publisher system  350 , possibly via a database or other source. Audio content item metadata extraction module  354  extracts audio content item metadata  356  from the received audio content items  352 . Extracted audio content item metadata  356  is received and processed by audio content item analysis module  358  to determine the “content source” and associated section(s) for each received audio content item  352 . Module  358  generates a set of analyzed metadata details  360 . 
     Ad hoc audio publication creation module  362  receives analyzed metadata details  360 , which include the determined content source and associated sections(s) for each audio content item  352 , and generates an ad hoc audio publication  368  for each unique content source. Referenced audio content items  352  are added to each generated ad hoc audio publication  368  by ad hoc audio publication creation module  362 . Ad hoc audio publications  368  are named according to the content source of the constituent audio content items (e.g., an ad hoc audio publication called “Podcasts” or “Blogs”). In an embodiment, notification module  370  may issue a notification  372  whenever a new or updated ad hoc audio publication is assembled by ad hoc audio publication creation module  362 . Notification  372  may be received by customization &amp; distribution system  110 , for example, to trigger the execution of customization processes enabled thereby. 
     One or more speech prompts  364  may be optionally selected by automated publisher system  350 . Speech prompts may be used, for example, during audio publication presentation to announce a selected ad hoc audio publication section name or the name of an ad hoc audio publication  368 . If speech prompts  364  are used, module  362  may add speech prompt presentation rules to the generated ad hoc audio publication metadata. Each generated ad hoc audio publication  368  includes audio publication metadata, one or more referenced audio content items  352 , and optionally, one or more referenced visual content items  366 , and one or more speech prompts  364 . 
     A.5. Example Audio Publication Archiving &amp; Retrieval Embodiments 
     Referring back to  FIG. 1 , audio publication archiving &amp; retrieval module  108  enables audio publications  118  to be stored (e.g., in assembled or disassembled form) and optionally reassembled at a later time. For example, an audio publication may be stored as a single object or alternatively in a “disassembled” form, such that the constituent audio publication components and metadata are stored as separate entities.  FIG. 4  depicts audio publication archiving &amp; retrieval system  400 , according to an example embodiment. Audio publication archiving &amp; retrieval system  400  is an example of audio publication archiving &amp; retrieval module  108  of  FIG. 1 . As shown in  FIG. 4 , system  400  includes an audio publication metadata processing module  408 , an audio publication assembly module  412 , and a plurality of databases  404 ,  414 ,  416 , and  418  that store audio publication components generated in modules  104  and  106  (of  FIG. 1 ). Databases  404 ,  414 ,  416 , and  418  are depicted as separate databases for ease of illustration and may be realized as one or more combined or separate physical databases. These elements of system  400  are described as follows. 
     Referring to  FIG. 4 , a query  402  for a particular audio publication  420  is received by system  400 . For example, query  402  may be received from a publisher, a subscriber (via presentation system  136  or subscriber portal  124 ), or from customization &amp; distribution system  110  of  FIG. 1 . Audio publication metadata  406  corresponding to query  402  is retrieved from audio publication metadata database  404  by audio publication metadata processing module  408 . Audio publication metadata processing module  408  parses audio publication metadata  406  and generates audio publication assembly directives  410 , which are received by audio publication assembly module  412 . Audio publication assembly directives  410  may include SQL (structured query language) statements and/or other code used to retrieve stored audio publication components and to assemble an audio publication, for example. 
     Audio publication assembly module  412  receives and utilizes audio publication assembly directives  410  to retrieve audio content items, visual content items, and speech prompts (e.g., “audio publication components”) referenced in audio publication metadata  406 . For example, as shown in  FIG. 4 , module  412  may request and receive one or more audio content items stored in audio content items database  414 , may request and receive one or more visual content items stored in visual content items database  416 , and/or may request and receive one or more speech prompts stored in speech prompts database  418 . The received audio publication components are assembled by audio publication assembly module  412  to generate a requested audio publication  420 . Assembled audio publication  420  may then be stored and/or transmitted to the entity or system that initiated the query. 
     B. Example Customization &amp; Distribution System Embodiments 
     Referring to  FIG. 1 , customization &amp; distribution system  110  transforms audio publications  118  into subscriber-defined custom audio publications  120 , manages subscriber access to custom audio publications  120 , and ensures timely delivery of custom audio publications  120  to a subscriber&#39;s presentation system. Customization &amp; distribution system  110  includes an audio publication customization module  112 , an optional advertisement selection &amp; scheduling module  114 , and an audio publication distribution module  116 . Audio publications are provided to customization &amp; distribution system  110  by audio publications database  118 . For example, as described above, customization &amp; distribution system  110  may generate queries to audio publication archiving &amp; retrieval module  108  for audio publications. Custom audio publications generated according to one or more audio publication customization techniques may be stored in custom audio publications database  120 . Additionally, subscriber details including current subscription information, audio content item presentation history, advertisement presentation history, and/or one or more custom audio publication templates, etc., may be stored in subscriber database  122 . 
     B.1. Example Audio Publication Customization Embodiments 
     Audio publication customization module  112  enables custom audio publications  120  to be generated.  FIG. 5A  depicts an audio publication customization system  500 , according to an example embodiment. Audio publication customization system  500  is an example embodiment of audio publication customization module  112  of  FIG. 1 . As shown in  FIG. 5A , system  500  includes a subscription filter  504 , a custom audio publication creation module  514 , a custom speech prompt creation module  518 , a TTS (text-to-speech) engine  520 , and a notification module  524 . These elements of system  520  are described as follows. 
     Referring to  FIG. 5A , subscription filter  504  is configured to limit a subscriber&#39;s access to a subset of available source audio publications  502  according to a subscriber&#39;s access privileges  508 , which may be stored in subscriber database  510  (e.g., subscriber database  122  of  FIG. 1 ). Filtered audio publications  506  are provided to custom audio publication creation module  514 , which dynamically generates one or more new custom audio publications according to one or more subscriber-defined custom audio publication templates  512  stored in subscriber database  510 . If custom audio publication templates  512  are not provided, filtered audio publications  506  may pass through custom audio publication creation module  514  unmodified. As shown in  FIG. 5A , custom audio publication creation module  514  generates custom and/or pass-through audio publications  516 . Audio publications  516  may be stored in custom audio publications database  522  (e.g., custom audio publications database  120  of  FIG. 1 ). Additionally, notification module  524  may send a notification  526  to audio publication distribution module  116  ( FIG. 1 ) whenever one or more new and/or updated audio publications  516  are generated and are available for distribution to a subscriber (see section B.4). 
     Optionally, custom speech prompt creation module  518  may generate one or more speech prompts for audio publications  516  generated by custom audio publication creation module  514 . Custom speech prompt creation module  518  may use computerized TTS (text-to-speech) engine  520  to generate one or more speech prompts automatically. As described elsewhere herein, speech prompts may be generated for each custom audio publication name and for each custom audio publication section, for example. If custom speech prompt creation module  518  generates speech prompts, custom audio publication creation module  514  may be configured to modify/update the audio publication metadata of a corresponding audio publication  516  to include the speech prompt presentation rules, as described elsewhere herein. 
     Audio publication customization system  500  may also be configured to generate updated audio publications  516  whenever corresponding source audio publications  502  are updated. For example, subscription filter  504  may receive an update notification  528  (e.g., from audio publication creation module  106 ) when one or more source audio publications  502  are updated. Furthermore, audio publication customization system  500  may be configured to execute upon receipt of update notification  528  such that only the new audio content items contained in source audio publications  502  are processed. 
     B.2. Example Custom Audio Publication Generation Embodiments 
     Custom audio publication creation module  514  of  FIG. 5A  enables one or more custom audio publications  516  to be generated by selecting audio content items from one or more source audio publications  502 .  FIG. 5B  shows a block diagram of a system  530 , which is an example of custom audio publication module  514  according to an example embodiment. System  530  is configured to select audio content items from source audio publications  532  and to generate one or more new custom audio publications  564 . As shown in  FIG. 5B , system  530  includes a static selection &amp; assignment module  548 , a keyword search-based selection module  552 , a relevance-based selection module  556 , rule selector modules  536 ,  540 , and  544 , and a custom audio publication assembly module  562 . These elements of system  530  are described as follows. 
     Referring to  FIG. 5B , source audio publications  532  and a subscriber-defined custom audio publication template  534  are received by system  530 . Rule selector  536  selects one or more subscriber-defined static selection and assignment rules  538  from custom audio publication template  534 , if such rules are present. Static selection &amp; assignment module  548  uses static selection &amp; assignment rules  538  to assign one or more audio content items contained in at least one source audio publication  532  to one or more sections contained within custom audio publication  564 . Static selection &amp; assignment rules  538  explicitly map one or more audio content items contained in source audio publications  532  to one or more custom audio publication sections defined by a subscriber. For example, static selection &amp; assignment rules  538  may be used to rename, reorder, or discard sections contained in a source audio publication  532 . Additionally, static selection &amp; assignment rules  538  may be used to select one or more audio content items from source audio publications  532  according to time-based selection criteria (e.g., audio content items that were created within the past week). Static selection &amp; assignment rules  538  may further be used to combine audio content items from a plurality of source audio publications  532  into a single custom section within custom audio publication  564 . Static selection &amp; assignment module  548  generates a set of assignment details  550  that are received by custom audio publication assembly module  562 . Assignment details  550  include the audio content item sectional assignments generated according to rules  538  for audio publications  532 . 
     Custom audio publication creation module  530  also enables audio content items to be selected dynamically according to subscriber-defined keyword search-based rules. For example, keyword search-based selection module  552  enables audio content items contained in one or more source audio publications  532  to be selected according to a provided keyword search expression. Rule selector  540  selects keyword search-based assignment rules  542  from customization template  534 , if such rules are present. One or more keyword search-based rules  542 , each including a keyword search expression and a corresponding custom section, may be defined in custom audio publication template  534 . Keyword search-based selection module  552  receives keyword search-based assignment rules  542  and source audio publications  532 , and selects matching audio content items as described below. 
       FIG. 5C  shows a block diagram of a system  570 , according to an example embodiment. System  570  is an example of keyword-search based selection module  552 . System  570  includes a search engine  576  and a custom section assignment module  580 . Audio content items  572  and a keyword search-based assignment rule  574  are received by system  570 . Keyword search-based assignment rule  574  includes a keyword search expression and a custom section to which matching audio content items  578  are added. Search engine  576  selects audio content items  572  that match the keyword search expression provided in keyword search-based assignment rule  574 . Matching audio content items  578  are output by search engine  576  and received by custom section assignment module  580 . Custom section assignment module  580  generates assignment details  582  which map matching audio content items  578  to the custom section defined in keyword search expression assignment rule  574 . Referring to  FIG. 5B , assignment details  582  of  FIG. 5C  are received by custom audio publication assembly module  562  as assignment details  554 . 
     Referring to  FIG. 5B , custom audio publication creation module  530  enables audio content items contained in source audio publications  532  to be selected based on content relevance. As described in section D.2, presentation system  136  enables subscribers to “track” audio content items of interest. Audio content item tracking enables subscribers to follow developments in selected audio content item content over a given period of time (e.g., a day, a week, etc.). Rule selector  544  selects previously “tracked” audio content items  546  from audio content item database  560  according to information contained in custom audio publication template  534 . Source audio publications  532  and one or more previously “tracked” audio content items  546  are received by relevance-based selection module  556 . Relevance-based selection module  556  selects new audio content items from source audio publications  532  based on relevance to previously “tracked” audio content items  546  as described below. 
       FIG. 5D  shows a block diagram of a system  584 , according to an example embodiment. System  584  is an example of relevance-based search module  556  of  FIG. 5C . System  584  includes a relevance analysis module  590 , an optional search engine  592 , and a “Tracked Content” section assignment module  596 . New audio content items  586  and previously “tracked” audio content items  588  are received by relevance analysis module  590 . Relevance analysis module  590  analyzes audio content items  586  for relevance to previously “tracked” audio content items  588 , possibly by using a relevance search engine  592 . Optionally, relevance analysis module  590  may be assisted by additional information. For example, a publisher may incorporate references in an audio content item&#39;s metadata to one or more related audio content items. Audio content items  586  scoring a high relevance match to one or more previously “tracked” audio content items  588  are output by relevance-based selection module  590  as relevant audio content items  594 . “Tracked Content” section assignment module  596  receives relevant audio content items  594  and generates assignment details  598  which map the relevant audio content items  594  to the “Tracked Content” custom audio publication section. Referring to  FIG. 5B , assignment details  598  are received by custom audio publication assembly module  562  as assignment details  558 . 
     As shown in  FIG. 5B , assignment details  550 ,  554 , and  558 , custom audio publication template  534 , and source audio publications  532  are received by custom audio publication assembly module  562 , and custom audio publication assembly module  562  generates custom audio publication  564 . Assignment details  550 ,  554 , and  558  map one or more selected audio content items contained in source audio publications  532  to one or more custom sections within custom audio publication  564 . Custom audio publication assembly module  562  assembles custom audio publication  564  by including referenced audio content items (and visual content items) from source audio publications  532  in one or more custom audio publication sections, as defined by assignment details  550 ,  554 , and  558 . Additionally, custom audio publication template  534  is used to provide a subscriber&#39;s desired ordering of custom sections within custom audio publication  564 . 
     B.3. Example Advertisement Selection &amp; Scheduling Embodiments 
     Referring to  FIG. 1 , advertisement selection &amp; scheduling module  114  may be included in interactive audio publication system  100  to select and schedule audio and visual advertisements for playback and/or display during presentation of an audio publication. Additionally, module  114  enables targeted advertisement selection by providing access to subscriber data such as audio content item presentation history, advertisement presentation history, custom audio publication templates, tracked audio content items, etc. 
     Within interactive audio publication system  100 , a subscriber&#39;s audio content item and advertisement presentation history, including audio content items previously “tagged” or “tracked” by the subscriber, and advertisements previously “tagged” by the subscriber (see section D.2) is collected and retained in subscriber database  122 . By reviewing a subscriber&#39;s audio content item and advertisement presentation history, a publisher or other advertisement selection entity may select targeted advertisements for presentation. Additionally, an analysis of a subscriber&#39;s audio content item and advertisement presentation history may be performed to select diverse and non-repetitive advertisements. Furthermore, a subscriber&#39;s advertisement presentation history serves as a useful reporting tool, enabling publishers and advertisers to determine the exact number of subscribers to whom an advertisement was presented and to gauge the overall effectiveness of an advertisement. 
       FIGS. 6A and 6B  depict example system embodiments of advertisement selection &amp; scheduling module  114 . For instance,  FIG. 6A  depicts a system  600  that is configured to select and schedule advertisements after one or more custom audio publications have been generated by audio publication customization module  112 .  FIG. 6B  depicts a system  650  configured to perform advertisement selection and scheduling automatically as audio content items are streamed to presentation system  136  on-demand. 
     Referring to  FIG. 6A , system  600  includes an advertisement selection module  606 , an advertisement scheduling module  616 , and a custom audio publication modification module  622 . These elements of system  600  are described as follows. 
     Referring to  FIG. 6A , audio and/or visual advertisements  602  (e.g., contained in a database) are received by advertisement selection module  606 . Advertisement selection module  606  may be configured to select advertisements  602  that are targeted to a subscriber&#39;s interests, for example. For instance, advertisement selection module  606  may be enabled to perform targeted advertisement selection by analyzing a newly-generated custom audio publication  604  or by utilizing various subscriber-centric data stored in subscriber database  608  (e.g., subscriber database  122  of  FIG. 1 ). Additionally, a subscriber&#39;s audio content item and advertisement presentation history  610 , which may indicate previously “tracked” audio content items and previously “tagged” audio content items and advertisements, may be utilized by advertisement selection module  606  during advertisement selection. Still further, one or more of a subscriber&#39;s custom audio publication templates  612  (which may indicate the subscriber&#39;s interests, etc.) may be used by advertisement selection module  606  to assist in advertisement selection. Advertisement selection module  606  outputs a set of selected advertisements  614 . 
     Advertisement scheduling module  616  receives and schedules selected advertisements  614  according to advertisement scheduling criteria  618 . Advertisement scheduling criteria  618  may indicate various advertising scheduling factors, including a scheduling order, a scheduling timing, etc. For example, according to criteria  618 , selected advertisements  614  may be ordered sequentially (e.g., according to the price paid for the advertisement by an advertiser), scheduled for presentation during playback of a specific audio content item or section, or scheduled using more general criteria (e.g., after a set number of minutes, after a set number of presented audio content items, etc.). Selected advertisements  614  may be scheduled for presentation at the beginning or end of any audio content item segment (i.e., the title, summary, or story body). Advertisement scheduling module  616  generates advertisement scheduling details  620  for selected advertisements  614 , which includes the set of selected advertisements  614  and advertisement scheduling information. Custom audio publication modification module  622  receives advertisement scheduling details  620  and custom audio publication  604 . Custom audio publication modification module  622  generates modified custom audio publication  624  as a modified form of custom audio publication  604  that includes advertisements. Custom audio publication modification module  622  inserts advertisement scheduling details  620  in the custom audio publication metadata of custom audio publication  604 , and includes any referenced advertisements  614  to generate modified custom audio publication  624 . 
     Referring to  FIG. 6B , system  650  is configured to select advertisements on-demand as audio content items  654  are delivered to a subscriber for presentation. System  650  includes an advertisement selection module  656  and an advertisement embedding module  670 . These elements of system  650  are described as follows. 
     When a subscriber selects an audio content item  654 , advertisement selection module  656  may select an advertisement for presentation from a plurality of available advertisements  652  (e.g., contained in a database). As shown in  FIG. 6B , advertisement selection module  656  receives audio content item  654 , advertisements  652 , advertisement presentation history  658 , and custom audio publication templates  660 . In addition to the requested audio content item  654 , a subscriber&#39;s audio content item and advertisement presentation history  658  as well as any available custom audio publication templates  660  may be used by advertisement selection module  656  for targeted advertisement selection as described previously. As shown in  FIG. 6B , advertisement embedding module  670  receives selected advertisement  664  and audio content item  654 . If advertisement selection module  656  selects an advertisement for presentation, indicated by selected advertisement scheduling details  664  in  FIG. 6B , the selected advertisement may be embedded within audio content item  654  by advertisement embedding module  670 , or alternatively output as a standalone advertisement  668 . If the selected advertisement (indicated by advertisement scheduling details  664 ) is embedded within audio content item  654 , advertisement embedding module  670  modifies/updates the metadata of audio content item  654  using advertisement scheduling details  664  (e.g., to indicate the length of the advertisement, when the advertisement is to be presented, etc.). Advertisement embedding module  670  generates modified audio content item  672 , which contains the selected advertisement and advertisement scheduling details  664 . 
     B.4. Example Audio Publication Distribution Embodiments 
     Referring to  FIG. 1 , in addition to performing audio publication customization and advertisement selection and scheduling, customization &amp; distribution system  110  also manages the distribution of custom audio publications  120  to subscribers via audio publication distribution module  116 .  FIG. 7A  shows a block diagram of a system  700 , which is an example embodiment of audio publication distribution module  116 . As shown in  FIG. 7A , system  700  includes a subscriber access module  704 , an audio publication component selector  716 , an audio publication delivery module  720 , a notification module  734 , and a presentation manager  726 . These elements of  FIG. 7A  are described as follows. 
     Referring to  FIG. 7A , one or more custom audio publications  714  are transferred to a subscriber&#39;s presentation system via a data communications network, such as the Internet. Any standard or proprietary data communication protocol (e.g., FTP, HTTP, RSS/Atom, etc.), wired or wireless, may be used to transfer audio publication components (i.e., audio publication metadata, audio content items, visual content items, speech prompts, and advertisements) included in custom audio publications  714  to a subscriber&#39;s presentation system. If a subscriber&#39;s presentation system supports wireless networking, selected audio publication components may be delivered to a subscriber using a wireless data communications network. 
     The transfer of custom audio publications  714  may be initiated manually by a subscriber or automatically by presentation manager  726  (e.g., according to a schedule). In either case, access to distribution module  116  is managed by subscriber access module  704 , which verifies a subscriber&#39;s credentials  706  stored in subscriber database  710  (e.g., subscriber database  122  of  FIG. 1 ), after an access request  702  is received by subscriber access module  704 . For instance, access request  702  may be received from presentation manager  726 , and may indicate desired audio publications and/or audio publication components, a delivery type, and/or further information. Optionally, notification module  734  may send a notification  736  to a subscriber or to presentation manager  726  when new and/or updated audio publications  714  are available. For example, notification module  734  may receive an update notification  730  from audio publication customization module  500 , shown in  FIG. 5A , when new and/or updated audio publications  714  are available. Additionally, notification module  734  enables an emergency or other time-sensitive announcement  732  (contained in a special audio publication) to be pushed to a subscriber for immediate presentation. 
     Audio publications  714  may be downloaded by presentation manager  726  in their entirety for offline presentation, or alternatively streamed to presentation manager  726  via a data communications network for presentation on-demand. For on-demand delivery, an audio publication&#39;s metadata is initially transferred to a subscriber&#39;s presentation manager  726 ; other audio publication components are streamed to the subscriber on-demand as the audio publication is presented. 
     Following a successful login by presentation manager  726  to system  700  via subscriber access module  704 , subscriber access module  704  generates a delivery request  712 , which includes a requested delivery type—“complete” or “on-demand”—and optionally, a set of requested audio publication components. As shown in  FIG. 7A , audio publication component selector  716  receives delivery request  712  and custom audio publications  714 . If a complete delivery is requested, audio publication component selector module  716  retrieves a subscriber&#39;s delivery history  708  and selects a set of audio publication components to transfer from available audio publications  714 . In an embodiment, audio publication components not previously delivered to presentation manager  726  are selected by audio publication component selector  716  for delivery. Alternatively, if delivery request  712  is on-demand, the specific audio publication component(s) requested in delivery request  712  are selected by module  716  for delivery to presentation manager  726 . As shown in  FIG. 7A , module  716  outputs selected audio publication components  718 . 
     Selected audio publication components  718  are received by audio publication delivery module  720 . Audio publication delivery module  720  processes and transmits selected audio publication components  718  (e.g., as described with regard to  FIG. 7B ) to presentation manager  726  (e.g., over a communications network) as transmitted audio publication components  722 . Presentation manager  726  is an example of presentation manager  138  of  FIG. 1 . Presentation manager  726  receives transmitted audio publication components  722  and processes them accordingly (see section D.8). In addition, presentation manager  726  transmits a runtime state  724  to audio publication delivery module  720 , which processes runtime state  724  as described below. Following a successful delivery of selected audio publication components  718  to presentation manager  726 , audio publication delivery module  720  generates delivery details  728  and updates the subscriber&#39;s audio publication component delivery history  708  with delivery details  728 . 
       FIG. 7B  shows a block diagram of a system  750 , according to an example embodiment. System  750  is an example of audio publication delivery module  720  of  FIG. 7A . Referring to  FIG. 7B , system  750  includes an encryption module  754 , a transfer manager  758 , a runtime state processor  768 , and a presentation manager  764 . These elements of system  750  are described as follows. 
     Audio publication components  752  (e.g., selected audio publication components  718  of  FIG. 7A ) to be delivered to a subscriber are received by system  750 . In an embodiment, a subset or all of audio publication components  752  may be received and encrypted by encryption module  754  (e.g., using public/private key encryption). Encryption module  754  generates encrypted audio publication components  756 , which are received by transfer manager  758 . Transfer manager  758  transmits encrypted audio components  760  to connected presentation manager  764  (e.g., presentation manager  726  of  FIG. 7A ) over a data communications network (see section D.8). In addition, presentation manager  764  transmits runtime state  762  to transfer manager  758  (see section D.2). Received runtime state  762  is transmitted to runtime state processor  768  as runtime state  766 , and runtime state processor  768  updates the subscriber&#39;s audio content item and advertisement presentation history  770  (e.g., contained in subscriber database  774 ), to include all audio content items marked “tracked,” and all audio content items and advertisements marked “tagged.” Additionally, received runtime state  766  may be stored in presentation system runtime state database  772  (e.g., contained in subscriber database  774 ). 
     C. Example Subscriber Portal Embodiments 
     Referring to  FIG. 1 , subscriber portal  124  enables subscribers to manage their subscription account, to configure custom audio publication templates, and to configure presentation system runtime preferences. subscriber portal  124  includes a subscriber enrollment module  126 , a subscriber account management module  128 , a custom audio publication configuration module  130 , a presentation system preferences configuration module  132 , and an optional presentation system  134 . As shown in  FIG. 1 , subscriber portal  124  is coupled to custom audio publications database  120  and subscriber database  122 . 
       FIG. 8  shows a block diagram of a system  800 , according to an example embodiment. System  800  is an example of subscriber portal  124  of  FIG. 1 . System  800  may be configured in several ways, and multiple embodiments of system  800  may coexist within interactive audio publication system  100 . For instance, system  800  is shown in  FIG. 8  as a graphical user interface (GUI). In one embodiment, system  800  may be implemented as an Internet Web site that may be accessed using a Web browser. Such a Web-based embodiment may optionally include a presentation system  844  to enable audio publication presentation via the Web. In another embodiment, system  800  may be implemented within presentation system  136  and accessed at runtime via presentation device  140 . As shown in  FIG. 8 , system  800  includes a GUI  802 , a subscriber access module  824 , a subscriber enrollment module  814 , a subscriber account management module  826 , a custom audio publication configuration module  836 , a presentation system runtime preferences configuration module  848 , and an optional presentation system  844 . 
     Referring to  FIG. 8 , GUI  802  provides a visual interface to system  800 , which may include a plurality of menus, controls, and/or views backed by data contained in subscriber database  804  (e.g., subscriber database  122 ). Subscribers interact with GUI  802  to generate and modify data stored in subscriber database  804 , which may include subscriber profiles  806 , custom audio publication templates  808 , presentation system runtime state data  810 , and presentation system runtime preferences  812 , for example. 
     New subscriber enrollment is handled by subscriber enrollment module  814 . A new subscriber  816  may interact with GUI  802  and/or subscriber enrollment module  814  to generate a subscriber profile  818 , which may be stored in subscriber profiles database  806 . Subscriber profile  818  may include a unique username and password used to identify and authenticate new subscriber  816  during subsequent access requests to system  800 . Subscriber profile  818  may additionally contain a subscriber&#39;s audio publication subscription information, payment information, email address, home address, phone number, age, gender, and/or other pertinent information. 
     A registered subscriber may gain access to system  800  by issuing an access request  820  received by subscriber access module  824 , and supplying valid access credentials to subscriber access module  824 . Subscriber access module  824  validates the provided access credentials by comparing them to subscriber access credentials  822  stored in subscriber profiles database  806 . Following a successful validation of supplied access credentials, GUI  802  may render and present one or more textual and/or graphical components, enabling the subscriber to perform a plurality of tasks. Examples of such tasks are described in turn below. 
     As shown in  FIG. 8 , GUI  802  is coupled to each of subscriber enrollment module  814 , subscriber access module  824 , subscriber account management module  826 , custom audio publication configuration module  836 , presentation system  844 , and presentation system runtime preferences configuration module  848 . In an embodiment, via GUI  802 , subscriber account management module  826  may enable current subscribers to manage their subscription account. As shown in  FIG. 8 , subscriber account management module  826  may include an update profile module  828 , a purchase subscriptions module  830 , a modify subscriptions module  832 , and a change payment plan/information module  834 . For example, subscribers may update their current profile using profile update module  828 , may purchase subscriptions to audio publications using purchase subscriptions module  830 , may modify their current audio publication subscriptions using modify subscriptions module  832 , and/or may change payment plan/information using change payment plan/information module  834 . 
     In an embodiment, via GUI  802 , custom audio publication configuration module  836  provides a set of graphical views and controls enabling subscribers to generate and modify one or more custom audio publication templates  808 . As shown in  FIG. 8 , custom audio publication configuration module  836  may include a create/delete custom audio publication templates module  838 , an add/delete/rename custom sections module  840 , and a define audio content item/section assignment rules module  842 . For instance, subscribers may be enabled to generate or delete custom audio publication templates  808  using create/delete custom audio publication templates module  838 ; add, delete, or rename custom sections within a selected custom audio publication template  808  using add/delete/rename custom sections module  840 ; and/or define audio content item assignment rules for each custom section using define audio content item/section assignment rules module  842 , possibly by using graphical “drag-and-drop” operations or other techniques to map selected audio content items to one or more custom sections (see section B.2). One or more updated custom audio publication templates  808  are stored in subscriber database  804 . 
     In an embodiment, system  800  may include an integrated presentation system  844 . For example, a Web-based embodiment of system  800  may contain a presentation system  844  enabling audio publications to be presented via a standard Web browser, possibly with the assistance of a plug-in (e.g., an ActiveX control or a Java Applet). Within presentation system  844 , custom audio publications may be accessed directly from custom audio publications database  846  (e.g., database  120  of  FIG. 1 ). Additionally, presentation system  844  may access, update, and store its runtime state  810  in subscriber database  804 . Runtime state  810  may also be enabled to be synchronized with a subscriber&#39;s other presentation system  136  during audio publication delivery (see section B.4). Optionally, a subscriber may manually initiate runtime state synchronization between presentation system  844  and one or more of a subscriber&#39;s other presentation systems  136 . 
     In an embodiment, via GUI  802 , subscribers can access presentation system runtime preferences configuration module  848  to view and configure presentation system runtime preferences  812  (see section D.4) for one or more presentation systems  136  and integrated presentation system  844 . Runtime preferences  812  may be stored in subscriber database  804 , enabling full restoration to a subscriber&#39;s presentation system(s)  136 , if necessary. 
     D. Example Audio Publication Presentation System Embodiments 
     Referring to  FIG. 1 , presentation system  136  enables a presentation of interactive audio publications to a subscriber. Presentation system  136  includes a presentation manager  138 , a presentation device  140 , and optional third-party support modules  142 . When present, third-party support modules  142  may include portable media players (PMPs) and software and/or drivers needed to interface with PMPs. Various embodiments of presentation system  136  are possible. For example, presentation device  140  may be implemented as a standalone hardware device (e.g., a laptop computer, a notebook computer, a smart phone, a handheld computer, a custom hardware device, etc.), an attachable device (e.g., a plug-in device), a software application targeted for a PMP, a smart phone, or other computing platform, or as any other suitable device mentioned elsewhere herein or otherwise known. Additionally, presentation manager  138  may be integrated with presentation device  140 , or it may alternatively be deployed as a separate application, such as an application to be executed on a subscriber&#39;s personal computer. In another embodiment, presentation system  136  may be embedded in a larger system, such as an in-vehicle entertainment system, etc. 
     D.1. Example Presentation System Runtime Mode Embodiments 
     In an embodiment, a presentation system may include three runtime modes—a “title mode,” a “summary mode,” and a “full story mode”—that may be alternately selected by a subscriber at runtime. Both of the title and summary modes enable subscribers to peruse an interactive audio publication relatively quickly and efficiently, while the full story mode provides subscribers with an increased level of content detail. 
     In the title mode, only the title segment for each audio content item is presented by default. Similarly, in the summary mode, only the title and summary segments are presented by default. In the title and summary modes, in an embodiment, a subscriber has to specifically request presentation of the audio content item segment(s) that are not presented by default. Conversely, in full story mode, each audio content item is presented in its entirety, unless a subscriber specifically preempts playback of an audio content item. These modes are summarized below in Table 2. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Presentation device runtime modes. 
               
            
           
           
               
               
            
               
                 Runtime 
                   
               
               
                 Mode 
                 Description 
               
               
                   
               
               
                 Title 
                 Useful for quickly browsing audio content item titles 
               
               
                 Mode 
                 Only the audio content item title segment presented by default 
               
               
                   
                 Subscriber must request presentation of the summary and 
               
               
                   
                 story body segments 
               
               
                 Summary 
                 Useful for browsing through audio publications 
               
               
                 Mode 
                 Only the audio content item title and summary segments 
               
               
                   
                 presented by default 
               
               
                   
                 Subscriber must request presentation of the story body 
               
               
                   
                 segment 
               
               
                 Full Story 
                 Audio content items played in their entirety 
               
               
                 Mode 
                 Subscriber must preempt playback of an audio content item 
               
               
                   
               
            
           
         
       
     
     In one embodiment, a desired summary segment length may be specified in the presentation system runtime preferences (see section D.4). For example, the desired summary segment length might be set by a certain number of introductory audio content item paragraphs. 
     D.2. Example Presentation System Runtime State Embodiments 
     During audio publication presentation, presentation system  136  maintains the complete state of each of a subscriber&#39;s audio publications, including the state of each audio content item and the state of each advertisement contained within the audio publications. The collective state that includes all audio publication states is called the presentation system runtime state. 
     An audio content item may be assigned to one of four states: “unhandled,” “played,” “skipped,” and “discarded.” Initially, each audio content item is in the unhandled state. An audio content item remains in the unhandled state until either its presentation completes normally (whereupon it enters the played state), or a subscriber preempts complete playback by navigating to another audio content item, section, or audio publication. If the subscriber preempts playback, but indicates a desire to resume playback at a later time, then the audio content item enters the skipped state. Otherwise, the audio content item enters the discarded state. 
     Additionally, an audio content item has two independent non-mutually exclusive status flags—“tracked” and “tagged”—that may be optionally set or cleared by a subscriber via presentation system  136 . Setting an audio content item&#39;s tracked flag indicates that the audio content item should be considered by audio publication customization module  112  when searching for relevant content during audio publication customization (see section B.2). Audio content item tracking enables subscribers to follow developments in selected topics of interest and to discover new audio content items with relevant story content, as described further below. 
     Audio content item “tagging” is a mechanism for marking audio content items so that they may be “post-processed” by a subscriber (e.g., shared with other subscribers, saved permanently to their account, etc.). Subscribers can access and post-process tagged audio content items from subscriber portal  124 , or possibly, directly from presentation device  140  (depending on the capabilities of the presentation device  140  embodiment). The audio content item states and status flags are summarized below in Table 3 and Table 4 respectively. 
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Audio content item states. 
               
            
           
           
               
               
               
            
               
                   
                 State 
                 Description 
               
               
                   
                   
               
               
                   
                 Unhandled 
                 A subscriber has not yet interacted with the audio 
               
               
                   
                   
                 content item 
               
               
                   
                 Played 
                 The audio content item has been presented in its 
               
               
                   
                   
                 entirety 
               
               
                   
                 Skipped 
                 The audio content item has been skipped 
               
               
                   
                   
                 temporarily; presentation may be resumed at 
               
               
                   
                   
                 a later time 
               
               
                   
                 Discarded 
                 The audio content item has been discarded; 
               
               
                   
                   
                 presentation cannot be resumed at a later time 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 Audio content item status flags. 
               
            
           
           
               
               
            
               
                 Status Flag 
                 Description 
               
               
                   
               
               
                 Tracked 
                 The audio content item will be considered by audio 
               
               
                   
                 publication customization module 112 when searching 
               
               
                   
                 for relevant content 
               
               
                 Tagged 
                 The audio content item is marked for “post- 
               
               
                   
                 processing” by a subscriber 
               
               
                   
               
            
           
         
       
     
     An advertisement may be in one of two states: “not played” and “played.” Additionally, an advertisement has a “tagged” flag that may be set by a subscriber during presentation of the advertisement. Tagging an advertisement enables a subscriber to review the advertisement at a later time, possibly via presentation device  140  or subscriber portal  124 . In one embodiment, tagging an advertisement may cause an email to be sent automatically to a subscriber&#39;s email address that is stored in their profile. For example, the email may contain a Web hyperlink to the advertisement, a digital media file containing the advertisement, or an alternative presentation of the advertisement including at least one of text, images, and/or audio. 
     A current presentation system runtime state may be transmitted to customization &amp; distribution system  110  during audio publication distribution and may be stored in subscriber database  122 . Optionally, the stored runtime state may be used to synchronize a plurality of presentation systems  136  that is tied to the same subscriber account. Runtime state synchronization enables the active presentation system to be changed (e.g., the subscriber may have more than one presentation system in their possession) during audio publication presentation and ensures that there are no discontinuities or inconsistencies when presentation is resumed on the new presentation system. 
     The runtime state also enables presentation system  136  to monitor a subscriber&#39;s progress through each audio publication. A subscriber can obtain real-time status reports indicating, for example, the number of unhandled or skipped audio content items in a section, the time required to present the remaining audio content items in a section (based on the current runtime mode), or the percentage of audio content items that have been handled (i.e., either played, skipped, or discarded). Reports may be delivered aurally, possibly by using a combination of prerecorded speech prompts and computerized text-to-speech, or alternatively delivered as text-based notifications. 
     D.3. Example Presentation System Subscriber Interface Embodiments 
     Subscribers may interact with presented audio publications using either a graphical user interface, a button interface (e.g., one or more buttons or a keyboard), a thumb wheel, a roller ball, a stick pointer, etc., and/or by using corresponding voice commands. The button interface may include either physical or virtual buttons. A virtual button interface may be realized, for example, by presenting button icons on a touch screen. 
     In an embodiment, a built-in speech recognition module enables true hands-free navigation of audio publications using an intuitive voice control interface. The voice control interface enables subscribers to interact with audio publications safely while driving, exercising, or multitasking. With speech recognition enabled, subscribers can navigate audio publications by issuing short voice commands. If desired, voice commands may be prefaced by a special trigger command (e.g., “reader” or the product&#39;s brand name) for better recognition accuracy in noisy environments. 
     Presentation system  136  defines several commands (shown in Table 6 further below) to facilitate interaction with audio publications. Commands may be categorized by function into four broad categories, such as “navigation,” “control,” “customization,” and “help.” Subscribers may navigate though audio publications and audio content items using navigation commands, manage audio content item presentation with control commands, customize audio publications and runtime preferences with customization commands, and obtain help using help commands. 
     Commands may be received from a subscriber at any point while presentation system  136  is active. Not all commands must be active at all times; disabled commands may be ignored by presentation system  136 . Alternatively, a short message may be played indicating the reason why a command could not be completed. For example, to ensure uninterrupted presentation of an advertisement, a majority of commands may be disabled while an advertisement is presented. 
     D.4. Example Presentation System Runtime Preferences Embodiments 
     Presentation system  136  provides several runtime preferences for customizing audio publication presentation. Examples of runtime preferences are shown below in Table 5. 
                     TABLE 5               Exemplary presentation system runtime preferences.                                    (1) Default runtime mode (title, summary, or full story mode)       (2) Desired summary length (e.g., as a number of introductory paragraphs)       (3) Enable/disable helpful speech prompts       (4) Enable/disable greeting                    
Separate runtime preferences for a plurality of subscribers may be stored on presentation device  140 , enabling a plurality of subscribers to share a presentation device. Preferences may be set via presentation device  140  (using the button interface, voice control interface, or other interface) or subscriber portal  124 . If the voice control interface is used, the preferences may be set interactively via a sequence of guided speech prompts.
 
     Presentation system  136  may also feature helpful speech prompts that may be selectively enabled or disabled in the runtime preferences. If enabled, various speech prompts may be played at key interaction points to assist subscribers as they become familiar with the presentation system command set and user interface. Additionally, an optional greeting may be selectively enabled or disabled in the runtime preferences, so that the greeting is played (or not played) when presentation device  140  is powered-on. An example greeting might greet a subscriber by name and announce the current date and time. 
     D.5. Example Audio Content Item Searching Embodiments 
     Presentation system  136  may be configured to enable subscribers to search for audio content items that satisfy a particular keyword search expression. Depending on the particular presentation system embodiment and whether a network connection is available, the search may be performed either locally or remotely, possibly by using search engine  576  ( FIG. 5C ) provided by customization &amp; distribution system  110 . The search scope may be restricted to the set of audio content items currently present on presentation system  136  or broadened to include a full set of audio content items accessible by a subscriber (e.g., according to their subscription). Alternatively, the search scope may be maximized to include all available audio content items, although access to one or more of the matching audio content items may require a subscription upgrade. 
     A keyword search expression may be dictated (e.g., by voice) or typed (e.g., by keyboard) if the presentation system embodiment provides a text entry interface. If the keyword search expression is dictated, speech recognition may either be performed locally on presentation device  140  by a speech recognition module (e.g., as described below with respect to  FIG. 10 ), or remotely by a separate speech recognition system. In the latter case, recorded audio comprising the keyword search expression may be transmitted directly to a remote speech recognition system, or alternatively preprocessed by presentation device  140  prior to transmission (e.g., to decrease the amount of data transmitted to the speech recognition system). 
     D.6. Example Visual Content Item Presentation 
     As discussed in section A.1, one or more visual content items may be scheduled for display during presentation of an audio content item. If presentation device  140  provides a visual display interface, visual content items may be presented according to scheduling details contained in an associated audio content item&#39;s metadata. In addition, a subscriber may alternately switch between an automatic presentation of visual content items and a manual browsing mode, in which the subscriber may freely browse available visual content items using voice commands or the button interface provided by presentation device  140 . 
     D.7. Example Audio Publication Built-in Sections 
     As described elsewhere herein, audio publications may include one or more sections, such that each section contains at least one audio content item. In an embodiment, interactive audio publication system  100  may provide three additional sections within each custom audio publication: “Tracked Content,” “Skipped Content,” and “Search Results.” 
     The “Tracked Content” section is compiled automatically during audio publication customization as new audio content items are analyzed for relevance with previously “tracked” audio content items (see section B.2). New audio content items scoring a high relevance match with one or more previously “tracked” audio content items are added automatically to the “Tracked Content” section, enabling subscribers to follow developments in selected topics of interest. 
     The “Skipped Content” section maintains a list of all audio content items that have been skipped temporarily during presentation of an audio publication. A subscriber may navigate to the “Skipped Content” section to access and replay any previously skipped audio content items. 
     The “Search Results” section is populated with the results from the most recent audio content item search (see section D.5) performed by a subscriber. The audio content items added to the “Search Results” section may be limited to those that are available for immediate presentation (e.g., based on the subscriber&#39;s subscriptions). 
     D.8. Example Presentation Manager Embodiments 
     As shown in  FIG. 1 , presentation manager  138  interfaces with presentation device  140  and audio publication distribution module  116 .  FIG. 9  shows a block diagram of a system  900 , according to an example embodiment. System  900  is an example of presentation manager  138  of  FIG. 1 . As shown in  FIG. 9 , system  900  includes a receive audio publications module  904 , a prepare audio publications module  908 , a transfer and remove audio publications module  912 , and a transmit runtime state module  916 . As shown in  FIG. 9 , a presentation device  914  (e.g., presentation device  140  of  FIG. 1 ) is coupled to transfer and remove audio publications module  912 . 
     Referring to  FIG. 9 , presentation manager  900  may be configured to access audio publication distribution module  116  of  FIG. 1  in any manner, including automatically according to a daily schedule, or in response to a notification from audio publication distribution module  116  indicating that one or more new and/or updated audio publications are available for download. Alternatively, a subscriber may manually initiate audio publication delivery. As described in section B.4, audio publication components (i.e., audio publication metadata, audio content items, visual content items, speech prompts, and advertisements) may be downloaded by presentation manager  900  either in bulk, or alternatively streamed on-demand as they are needed for presentation. 
     Following a successful login to audio publication distribution module  116  by presentation manager  900 , receive audio publications module  904  issues a request for either an entire interactive audio publication (complete download) or alternatively, for one or more audio publication components needed for imminent presentation (e.g., for on-demand delivery). At the same time, presentation system runtime state  918  may be transmitted by transmit runtime state module  916  to distribution module  116 . As discussed in section D.2, presentation system runtime state  918  collectively includes the state of each of a subscriber&#39;s audio publications and enables the active presentation system to be changed during audio publication presentation. Additionally, runtime state  918  may be used to update a subscriber&#39;s audio content item and advertisement presentation history, and may be utilized for targeted advertising as described in section B.3. 
     New and/or updated audio publications  902  (or individual audio publication components) are received by module  904 . Received audio publications  906  (or audio publication components) are prepared for presentation on presentation device  914  by module  908 . Module  908  may be configured to support audio publication presentation on any number of implementations of presentation device  914 . For example, a plug-in presentation device implementation may depend on a connected PMP for audio playback and visual display functionalities. In addition, the PMP may prevent access to its file system, thereby disallowing presentation device  914  from reading audio content item metadata and audio publication metadata directly from disk. To bypass this limitation, module  908  may split each audio content item into separate audio content item fragments, as described herein. Additionally, at least a portion of the information contained in the audio content item and audio publication metadata may be retained by employing a file naming convention that encodes portions of the metadata in the audio content item fragment filenames, and by utilizing separate audio file playlists corresponding to the individual audio publication sections. Such preprocessing may enable presentation device  914  to recreate the audio content item and audio publication metadata by parsing the playlists and the audio content item fragment filenames. 
     In another possible embodiment of presentation manager  900 , audio publications may be adapted for playback on standard PMPs (i.e., without presentation device  914 ). In such an embodiment, audio content item audio data may be packaged into separate audio files. Using audio publication metadata, module  908  may organize the audio files into separate playlists corresponding to the individual audio publication sections. Additionally, advertisements may be inserted into a subset of the audio files according to advertisement scheduling details contained in the audio publication metadata. Furthermore, visual content items may be embedded in the album artwork ID3 tag (or equivalent tag) of associated audio files for display during playback. 
     Prepared audio publications  910  (or audio publication components) are transferred by module  912  to presentation device  914 . In addition, old audio publications may be removed automatically from presentation device  914  by module  912  according to a subscriber&#39;s presentation system runtime preferences or if presentation device  914  has limited storage capacity. Various techniques for transferring audio publication components to/from presentation device  914  may be used by module  912 . In one embodiment, audio publication components may be stored in a database that is shared between presentation manager  900  and presentation device  914 . Alternatively, for PMP-based embodiments, PMP management software (or another third-party module  142 ) may be used to transfer prepared audio publications  910  and remove old audio publications to/from presentation device  914 . 
     D.9. Example Presentation Device Embodiments 
     Referring to  FIG. 1 , presentation device  140  provides a core user interaction experience with interactive audio publications. Presentation device  140  receives audio publications from presentation manager  138  and presents them to a subscriber interactively. For example, a subscriber may be enabled to listen to one or more audio publications using presentation device  140 . Presentation device  140  may include or be coupled to one or more speakers to enable the subscriber to hear the audio publication. For instance, headphones may be coupled to presentation device  140  to enable the subscriber to listen to the audio publication, including listening to the audio publication in situations where the subscriber desires to be more discreet (e.g., when listening to the audio publication at work or in another public place, such as a store, a restaurant, an airplane, or while using public transportation, etc.). If an audio publication includes video, the subscriber may be enabled by presentation device  140  to view the video (e.g., on a display of presentation device  140 ). If the audio publication includes advertisements, presentation device  140  may enable the advertisements to be played (for an audio advertisement) and/or displayed (for a video advertisement) to the subscriber. One or more audio publications may be stored on presentation device  140  at any time, and the active audio publication may be changed as desired by the subscriber at runtime. 
       FIG. 10  shows a block diagram of a system  1000 , according to an example embodiment. System  1000  is an example of presentation device  140  of  FIG. 1 . System  1000  includes a plurality of modules that may be implemented using hardware, software, or a combination of hardware, software, and/or firmware. As shown in  FIG. 10 , system  1000  includes a presentation device executive logic  1002 , a user interface adapter  1004 , a PMP adapter  1006 , an audio output interface  1008 , an external peripheral interface  1010 , a display interface  1012 , a physical button interface  1016 , a virtual button interface  1018 , a voice control interface  1020 , a database  1040 , an optional PMP  1042 , optional media codecs  1044 , a TTS (text-to-speech) engine  1046 , and an optional display  1048 . Voice control interface  1020  includes an audio capture module  1030 , an analog to digital converter  1034 , and a speech recognition module  1038 . These elements of system  1000  are described as follows. 
     Referring to  FIG. 10 , in an embodiment, presentation device executive logic  1002  is logic (e.g., an application, one or more processors and/or circuits, etc.) that manages a plurality of connected components. Presentation device executive logic  1002  provides a core application logic and control and uses “interface/adapter” modules  1004 ,  1006 ,  1008 ,  1010 , and  1012  to interface with supporting modules, thereby facilitating alternative presentation device embodiments. 
     Presentation device  1000  uses presentation manager  1014  (see section D.8) to handle all aspects of audio publication preparation, transfer, and removal to/from presentation device  1000 . Depending on a particular presentation system embodiment, presentation device executive logic  1002  may interface either directly or indirectly with presentation manager  1014 . In an indirect interface configuration, one or more third-party support modules  142  ( FIG. 1 ) (e.g., a PMP, PMP management software, etc.) may provide a bridge between presentation device executive logic  1002  and presentation manager  1014 . 
     Subscribers may interact with presentation device  1000  via a button interface (optionally a physical button interface  1016  or a virtual button interface  1018 ) and/or a voice control interface  1020 . Any of the available interfaces may be used to enter commands to presentation device  1000 , and commands may be received from a subscriber at any time. A subscriber command  1022 ,  1024 , or  1026  that is entered using physical button interface  1016 , virtual button interface  1018 , or voice control interface  1020  respectively, is received by presentation device executive logic  1002  via user interface adapter  1004 . User interface adapter  1004  enables presentation device executive logic  1002  to execute independently of the actual control interface utilized by a subscriber. 
     Voice control interface  1020  may be selectively enabled or disabled as necessary. If voice control interface  1020  is enabled, voice commands (examples are included in Table 6 further below) may be used to control presentation device executive logic  1002 . Analog audio  1028  is captured by audio capture module  1030  using a microphone or a microphone array. Audio capture module  1030  generates captured audio signal  1032 . Captured audio signal  1032  is converted to digital audio samples  1036  by analog to digital converter  1034 . Generated digital audio samples  1036  are received by speech recognition module  1038 , which is described below. 
       FIG. 11  shows a block diagram of a system  1100 , according to an example embodiment. System  1100  is an example of speech recognition module  1038  of  FIG. 10 . System  1100  includes an acoustic echo canceller  1110 , a speech detector  1114 , and a speech recognizer  1118 . These elements of system  1100  are described as follows. An input audio signal  1108  may contain one or more of the following audio components: a subscriber utterance (i.e., a possible voice command)  1102 , loudspeaker output  1104  as an audio content item is played, and background noise  1106 . Acoustic echo canceller  1110  receives input audio signal  1108 , removes loudspeaker output  1104  from input audio signal  1108 , and outputs echo-suppressed audio signal  1112 . Speech detector  1114  receives echo-suppressed audio signal  1112  and discriminates between speech and background noise  1106 , enabling only speech signals to pass through. In one embodiment, speech detector  1114  is an algorithm (e.g., an application) that performs speech detection automatically. Alternatively, speech detector  1114  may be a push-to-talk button, enabling speech detection to be performed manually by a subscriber. Speech detector  1114  outputs speech audio signal  1116 , which may contain some background noise  1106 . 
     Speech recognizer  1118  receives and processes audio speech signal  1116  to identify a possible spoken command  1120 . A plurality of speech recognition grammars  1122  may be used by speech recognizer  1118  to restrict the set of acceptable voice commands based on a current state of presentation device executive logic  1002 , for example. Additionally, speech recognition grammars  1122  may be used to improve recognition accuracy, to decrease computational requirements, and to clarify misunderstood (or low-confidence) commands through an interactive dialog using speech prompts. If subscriber utterance  1102  contains a voice command, a corresponding decoded voice command  1120  is output from system  1100 . 
     Referring to  FIG. 10 , audio publication components are received by presentation device executive logic  1002  from presentation manager  1014 , or alternatively via a third-party module  142 , such as a PMP  1042 . Presentation device executive logic  1002  parses and transforms received audio publication metadata into an equivalent representation that may be stored in database  1040 . Database  1040  may also maintain the local presentation system runtime state (see section D.2) and may also store the presentation system runtime preferences (see section D.4). 
     In an embodiment, audio and/or video decoding and playback may be performed using a third-party module  142  such as a PMP  1042 , or alternatively, using media codecs  1044 , audio output interface  1008 , and/or display interface  1012 . In PMP-based embodiments, presentation device executive logic  1002  interfaces with a connected PMP  1042  through PMP adapter  1006 , which may be an interface that enables a variety of PMPs  1042  to be used with presentation device executive logic  1002 . 
     Presentation device executive logic  1002  may use audio output interface  1008  and TTS (text-to-speech) engine  1046  to generate speech prompts and status reports at runtime, as described above, and to provide audible help. 
     In certain embodiments, presentation device  1000  may have access to an external display  1048  (or touch screen) which may be used to present images, videos, and possibly a virtual button interface  1018 . If display  1048  is available, presentation device executive logic  1002  interfaces with display  1048  though display interface  1012 . If display  1048  is a touch screen, a virtual button interface  1018  may be provided to render buttons and controls on display  1048  and to process user input in the form of screen touches and gestures. 
     In some embodiments, presentation device  1000  may enable interfacing with external hardware devices. For example, external peripheral interface  1010  may enable presentation device  1000  to be controlled remotely and/or to receive firmware upgrades from a connected computer. Hardware peripheral interface  1010  may also provide connections to route audio to headphones or external speakers, and to receive audio via an external microphone. 
     D.10. Further Example Presentation Device Embodiments 
       FIG. 12  depicts a block diagram of a system  1200 , according to an example embodiment. System  1200  shows a block diagram of an example of presentation device  140  of  FIG. 1 . As shown in  FIG. 12 , system  1200  includes one or more CPU(s)  1202 , a non-volatile memory  1204 , a RAM (random access memory)  1206 , an optional PMP (portable media player)  1212 , a power source  1214 , a microphone  1218 , an analog-to-digital converter  1224 , an automatic gain control  1220 , a processor GPIO (general purpose input/output)  1228 , a physical button interface  1230 , one or more LEDs (light emitting diodes)  1232 , an analog-to-digital converter  1234 , a digital-to-analog converter  1238 , an audio mixer  1242 , and a volume control  1246 . Although not shown in  FIG. 12 , system  1200  may include a body or casing in which the elements shown in  FIG. 12  are incorporated and/or enclosed. These elements of system  1200  are described as follows. 
     System  1200  includes one or more CPUs  1202  that may be capable of running an operating system (e.g., embedded Linux, etc.). Non-volatile memory  1204  (e.g., flash memory, ROM, etc.) may be used to store prerecorded speech prompts and default runtime preferences, and RAM  1206  may provide working memory for presentation device executive logic  1002  ( FIG. 10 ). System  1200  may receive power  1210  from optionally connected PMP  1212  via bus  1210 , or from another internal or external power source  1214 . Example power sources include an internal rechargeable battery or an external DC supply (e.g., a cigarette lighter). CPU(s)  1202  interfaces with optional PMP  1212  via a data communications interface  1208 , which may be USB, serial, or another interface type. 
     Input analog audio signal  1216  is captured by microphone  1218  (or a microphone array). Optionally, automatic gain control  1220  may be used to control the gain of microphone  1218  so as to maximize a dynamic range of input analog audio signal  1216  while avoiding clipping. Microphone  1218  outputs captured audio signal  1222 . Captured audio signal  1222  is converted to a digital signal  1226  by analog-to-digital converter (ADC)  1224 . Processor GPIO  1228  (general purpose input/output) may be used by CPU(s)  1202  to receive control commands from physical button interface  1230 . Processor GPIO  1228  may also be used by CPU(s)  1202  to control one or more system status LEDs  1232 . 
     When present, optional PMP  1212  may provide audio and/or video decoding and playback functionalities (e.g., when such decoding and playback functionalities are not handled by CPU(s)  1202  and/or other portions of system  1200  other than PMP  1212 ). Optionally, analog-to-digital converter (ADC)  1234  may be used to sample analog audio signal  1236  output from PMP  1212 , enabling cancellation of audio signal  1236  to be performed using a standard DSP (digital signal processing) algorithm. Prerecorded speech prompts and dynamically generated text-to-speech audio output by CPU(s)  1202  may be played using digital-to-analog converter (DAC)  1238 . Audio mixer  1242  combines audio signal  1236  output from optional PMP  1212  with audio signal  1240  output by DAC  1238  to generate mixed audio signal  1244 . Volume control  1246  applies an amplification gain to mixed audio signal  1244  yielding output audio signal  1248 . 
     D.11. Exemplary Plug-In Presentation Device Embodiments 
     In embodiments, system  1200  may be implemented directly in a mobile device, such as a PMP, a smart phone, a laptop computer, or other such device mentioned elsewhere herein or otherwise known. In another embodiment, system  1200  may be implemented in an attachable device (e.g., a plug-in module or device) that may be coupled (e.g., plugged-in) to another device or system to enable the functionality described herein, possibly by using one or more functionalities provided by the other device or system (e.g., digital audio and/or video decoding and playback/display, speech recognition, etc.). For instance,  FIG. 13  depicts a view of a plug-in device  1300 , according to an example embodiment. Plug-in device  1300  is an example embodiment of presentation device  140 , and in embodiments, may include some or all of the features of system  1200  of  FIG. 12 . Plug-in device  1300  is configured to interface with a mobile device (e.g., a PMP) that may enable digital audio playback and/or video display functionalities. For example, system  1300  may be plugged into an interface (e.g., a connector) of the mobile device. 
     Referring to  FIG. 13 , plug-in device  1300  includes a plurality of control interfaces positioned on a rectangular body. As shown in  FIG. 13 , plug-in device  1300  includes a “read” button  1302 , a play/pause button  1304 , a next paragraph button  1306 , a previous paragraph button  1308 , a next audio content item button  1310 , a previous audio content item button  1312 , a volume up/down button  1314 , a tag button  1316 , a track button  1318 , a discard button  1336 , a clickable scroll wheel  1320 , a toggle button  1322 , and a preferences modify button  1326 . The control interfaces shown in  FIG. 13  for plug-in device  1300  are provided for purposes of illustration. Additional, fewer, and/or alternative control interfaces that provide corresponding functionality may be present in plug-in device  1300  in embodiments. Furthermore, although control interfaces are shown in  FIG. 13  in the form of buttons and a scroll wheel, each control interface may have any other form, virtual or physical, as described herein or otherwise known. Furthermore, the control interfaces of plug-in device  1300  may be positioned on plug-in device  1300  in any arrangement. The control interfaces are described as follows. 
     As shown in the example of  FIG. 13 , “read” button  1302 , play/pause button  1304 , next paragraph button  1306 , previous paragraph button  1308 , next audio content item button  1310 , previous audio content item button  1312 , volume up/down button  1314 , tag button  1316 , and track button  1318  are located on a common planar surface of the body of plug-in device  1300 . “Read” button  1302  may be pressed by a subscriber in title or summary mode (see section D.1) to request playback of an audio content item&#39;s summary or story body segment. As shown in the example of  FIG. 13 , read button  1302  is larger than other buttons of plug-in device  1300  and is centrally located on the planar surface. Play/pause button  1304  enables a user to play or pause a currently selected audio content item. Next paragraph button  1306  enables a user to advance to a next paragraph of a currently selected audio content item. Previous paragraph button  1308  enables a user to go to an earlier paragraph of a currently selected audio content item. Next audio content item button  1310  enables a user to advance to a next audio content item (e.g., in the current audio publication section). Previous audio content item button  1312  enables a user to go to a previous audio content item. Volume up/down button  1314  enables a user to increase or decrease the audio volume of audio played by plug-in device  1300 . Tag button  1316  enables audio content item and advertisement tagging, track button  1318  enables audio content item tracking, and discard button  1336  allows a currently selected audio content item to be permanently discarded as described in section D.2. 
     Clickable scroll wheel  1320  is located on a first edge (e.g., a right side edge in  FIG. 13 ) of the body of plug-in device  1300 . Clickable scroll wheel  1320  may provide multiple functions. For example, clickable scroll wheel  1320  may be configured to enable navigation among a plurality of audio publications and/or a plurality of audio publication sections, to enable the presentation system runtime preferences to be modified, and/or to enable a PMP&#39;s graphical display to be interacted with, if applicable. Toggle button  1322  is located on a second edge (e.g., a left side edge in  FIG. 13 ) of the body of plug-in device  1300 . Toggle button  1322  alternately enables/disables a voice control interface. Preferences modify button  1326  is located on a second edge (e.g., a left side edge in  FIG. 13 ) of plug-in device  1300 . Preferences modify button  1326  may be pressed to activate a mode enabling the runtime preferences to be modified. 
     As shown in  FIG. 13 , the body of plug-in device  1300  includes further features, including an LED  1324 , an audio input jack  1328 , an audio output jack  1330 , a hardware peripheral port  1332 , and a connector  1334 . LED  1324 , audio input jack  1328 , and audio output jack  1330  are each located on the planar surface of the body of plug-in device  1300 . LED  1324  may be configured to emit light when the voice control interface is enabled. An external microphone or microphone array may be connected to plug-in device  1300  via audio input jack  1328 , enabling plug-in device  1300  to be controlled using voice commands. Audio output jack  1330  enables audio to be routed externally to a pair of headphones or external speakers. Hardware peripheral port  1332  is located on a third edge (e.g., a bottom side edge in  FIG. 13 ) of plug-in device  1300 . Hardware peripheral port  1332  may be present to provide serial and USB connectivity, which may enable plug-in device  1300  to be controlled remotely and/or to receive firmware updates. Connector  1334  is located on a fourth edge (e.g., a top side edge in  FIG. 13 ) of plug-in device  1300 . Connector  1334  enables plug-in device  1300  to interface with a connected mobile device. For example, connector  1334  may enable plug-in device  1300  to be connected to an industry standard or proprietary interface of an electronic device such as a laptop computer, a tablet computer, a portable music player (e.g., an Apple® iPod®), a smart phone (e.g., an Apple® iPhone®, a phone that incorporates the Google Android™ platform, a RIM Blackberry® device), other mobile computer, etc. 
     D.12. Presentation Device Executive Main Process 
     The presentation devices described herein may operate in various ways to perform their functions. For instance,  FIGS. 14A-19  depict example processes that may be performed by presentation device executive logic  1002  ( FIG. 10 ) or other controlling logic of a presentation device. Throughout the referenced figures, the abbreviation “ACI” is used to denote “audio content item.”  FIGS. 14A-14B  are described as follows, and  FIGS. 15-19  are described in subsequent sections. 
       FIGS. 14A-14B  depict a flowchart  1400  for a process for playing audio publications, according to an example embodiment. Flowchart  1400  may be performed by presentation device executive logic  1002  of  FIG. 10 , for example. Further structural and operational embodiments will be apparent to persons skilled in the relevant art(s) based on the discussion regarding flowchart  1400 . Note that the steps of flowchart  1400  need not necessarily be performed in the order shown in  FIGS. 14A-14B . Furthermore, in embodiments, each of the steps of flowchart  1400  (and of further flowcharts described herein) may be performable by one or more sub-steps, depending on the particular implementation. Flowchart  1400  is described as follows. 
     Referring to  FIG. 14A , at step  1402 , an application is started. For example, the application may be presentation device executive logic  1002 . After step  1402 , flowchart  1400  enters “Initialization” process  1404 , an example of which is shown in  FIG. 15  and described in section D.13. According to process  1404 , presentation device executive logic  1002  may be initialized. After process  1404 , flowchart  1400  enters a “Handle Command” process  1406 , an example of which is shown in  FIGS. 16A-16D  and described in section D.14, where a subscriber-issued command is awaited. According to process  1404 , one or more commands that may be received by presentation device executive logic  1002  may be processed. 
     If no commands are received in “Handle Command” process  1406 , in decision block  1408 , a check for network connectivity is performed. If network connectivity for the presentation device is determined to be present, decision blocks  1410  and  1418  may determine whether additional commands have been received from a subscriber. For example, decision block  1410  determines whether to perform a complete download of available audio publications. If it is determined that available audio publications are to be downloaded, a complete audio publication download may be performed in step  1412 , and flowchart  1400  proceeds to “Initialization” process  1404  (as indicated by an exit point  1414  to entry point  1416  path in  FIG. 14A ). Decision block  1418  determines whether the presentation system runtime state should be synchronized. If it is determined that the presentation system runtime state should be synchronized, flowchart  1400  proceeds to “Initialization” process  1404  (as indicated by exit point  1414  to entry point  1416  path). If it is determined at decision blocks  1410  and  1418  that neither of the commands are received from a subscriber, or if there is determined to be no network connectivity at decision block  1408 , operation proceeds to “Handle Command” process  1406 . 
     If a “resume” command is received in “Handle Command” process  1406 , and this is a first “resume” command issued following application startup in step  1402 , then operation proceeds from “Handle Command” process  1406  to decision block  1422  (via “Change Section” entry point  1420 ). Decision block  1422  performs a preliminary determination of whether all downloaded audio content items have been played or discarded. If there are no remaining audio content item to play, operation proceeds to step  1426 . In step  1426 , a speech prompt  1424  is played to the subscriber, playback is stopped in step  1428 , and operation proceeds back to “Handle Command” process  1406  to await additional commands. If it is determined that there are remaining audio content items to play at decision block  1422 , operation proceeds to step  1430 . In step  1430 , the current section name is announced to the subscriber, such as by using a prerecorded speech prompt or generated text-to-speech. 
     Operation proceeds from step  1430  to decision block  1432  (shown in  FIG. 14B ). Decision block  1432  determines whether the current section contains any unhandled audio content items. If there are no remaining unhandled audio content items in the current section, operation proceeds to decision block  1434 . Decision block  1434  determines whether there are any audio content items in the current section that have been skipped. If decision block  1434  determines that there is at least one skipped audio content item, operation proceeds to step  1438 . In step  1438 , speech prompt  1436  is played to the subscriber to ask whether the skipped audio content item(s) should be played, and operation proceeds to decision block  1440 . In decision block  1440 , it is determined whether the subscriber indicates that the skipped audio content item(s) should be played. If so, operation proceeds to step  1442 , and if not, operation proceeds to step  1450 . In step  1442 , the current section is switched to “Skipped Content,” and operation proceeds to step  1446 . In step  1446 , a speech prompt  1444  is played to the subscriber to announce that the section is changing, and operation proceeds to “Change Section” entry point  1420  ( FIG. 14A ) via exit point  1448 . In step  1450 , a next audio publication section with at least one unhandled or skipped audio content item is selected, and operation proceeds to step  1446 . If it is determined at decision block  1434  that there are no skipped audio content items, operation proceeds to step  1454 . In step  1454 , a speech prompt  1452  is played to the subscriber announcing that there are no audio content items left to play in the current section, and operation proceeds to step  1450 . 
     If it is determined in decision block  1432  that the current section contains at least one unhandled audio content item, operation proceeds to step  1456 . In step  1456 , a next unhandled audio content item in the current section is retrieved, and operation branches into two concurrent paths. A first execution path (e.g., left-hand in  FIG. 14B ) handles audio content item and advertisement presentation, while a second execution path (e.g., right-hand in  FIG. 14B ) awaits and processes interaction commands (e.g., see Table 6 further below). 
     According to the first execution path, operation proceeds to a decision block  1458 . At decision block  1458 , it is determined whether an advertisement is to be presented. Such determination may be made based on advertisement scheduling details which may be present in the audio publication metadata of the currently selected audio publication. If an advertisement is to be presented, operation proceeds to step  1460 . In step  1460 , the selected advertisement is presented and a subset of the subscriber commands (e.g., see Table 6) may optionally be disabled. As described in section B.3, advertisements may be scheduled for presentation at the beginning and/or the end of a selected audio content item segment. Thus, decision block  1458  and step  1460  may be located and/or repeated together in a variety of positions along the left-hand execution path of flowchart  1400 . Decision block  1458  and step  1460  are indicated in  FIG. 14  in corresponding locations for illustrative purposes. 
     Following presentation of an advertisement in step  1460 , or if decision block  1458  determines that no advertisement is to be presented, in step  1462 , the current audio content item&#39;s title segment is played. When playback of the title segment has completed, operation proceeds to decision block  1464 . In decision block  1464 , the current runtime mode (see section D.1) is queried to determine whether the “title mode” is selected. If title mode is selected, operation proceeds to “Handle Title Mode” process  1466 , an example of which is shown in  FIG. 17  and described in section D.15. In “Handle Title Mode” process  1466 , it is determined whether the current audio content item&#39;s summary segment is to be played. Decision block  1468  evaluates the return value of process  1466  and determines whether playback of the summary segment is to commence by proceeding to step  1470 , or whether the next audio content item is to be retrieved by proceeding to “Next ACI” entry point  1474  (shown in  FIG. 14A ) via exit point  1472 . If decision block  1464  determines that title mode is not selected, operation proceeds to step  1470 . In step  1470 , the summary segment is played automatically. 
     Upon completion of the summary segment in step  1470 , operation proceeds to decision block  1476 . At decision block  1476 , it is determined whether the current runtime mode is either “summary mode” or “title mode.” If summary mode or title mode is selected, then operation proceeds to a “Handle Summary Mode” process  1478 , an example of which is shown in  FIG. 18  and described in section D.16. In “Handle Summary Mode” process  1478 , it is determined whether the current audio content item&#39;s story body segment is to be played. Decision block  1480  evaluates the return value of process  1478  and determines whether playback of the story body segment is to commence by proceeding to step  1482 , or whether the next audio content item is to be retrieved by proceeding to decision block  1432  (via exit point  1472  to “Next ACI” entry point  1474 , shown in  FIG. 14A ). If decision block  1476  determines that neither summary mode nor title mode is selected, the story body segment is played automatically in step  1482 . 
     If the current runtime mode is “full story mode,” neither “Handle Title Mode” process  1466  nor “Handle Summary Mode” process  1478  executes, and the title, summary, and story body audio content item segments are played consecutively in steps  1462 ,  1470 , and  1482  respectively. Upon completion of the story body segment in step  1482 , operation proceeds to “Handle Played Audio Content Item” process  1484 , an example of which is shown in  FIG. 19  and described in section D.17. Operation proceeds from process  1484  to decision block  1432  (via exit point  1472  to “Next ACI” entry point  1474 , shown in  FIG. 14A ) to retrieve a next audio content item for presentation. 
     According to the second execution path, a “Handle Command” process  1486  handles any commands that are entered using button interfaces  1016  and  1018 , voice control interface  1020  (see section D.3 and Table 6), and/or another suitable interface. Operation remains in “Handle Command” process  1486  until a valid command is received and processed, or playback is stopped (or paused), as determined by decision block  1488 . In decision block  1488 , if it is determined that playback is stopped (or paused), operation proceeds back to “Handle Command” process  1406  ( FIG. 14A ) to await additional commands. 
     D.13. Presentation Device Executive “Initialization” Process 
       FIG. 15  depicts a flowchart  1500  for an example “Initialization” process, according to an example embodiment. Flowchart  1500  may be performed by presentation device executive logic  1002  of  FIG. 10 , for example. In an embodiment, flowchart  1500  may be performed in process  1404  of flowchart  1400  ( FIG. 14A ). Following entry at step  1502 , flowchart  1500  branches into two concurrent paths. Along a first (e.g., left-hand in  FIG. 15 ) execution path, operation proceeds to decision block  1504 , and along a second (e.g., right-hand in  FIG. 15 ) execution path, operation proceeds to step  1512 . In decision block  1504 , it is determined whether this is the first execution of flowchart  1500  following completion of step  1402  in flowchart  1400 . If it is determined not to be the first execution of flowchart  1500  (e.g., flowchart  1500  was entered via entry point  1416 ), the left-hand execution path terminates, and at step  1522 , operation proceeds back to flowchart  1400 . If it is determined to be the first execution of flowchart  1500 , operation proceeds to step  1506 . In step  1506 , runtime preferences (see section D.4) are retrieved and processed, and operation proceeds to decision block  1508 . In decision block  1508 , it is determined whether a greeting is to be played to the subscriber. If a greeting is determined to be played, operation proceeds to step  1510 . In step  1510 , a greeting is played to the subscriber. If a greeting is determined not to be played, operation proceeds to step  1522 . 
     In parallel, along the right-hand execution path, at step  1512 , new and/or updated audio publication metadata is retrieved from presentation manager  138  or a connected third-party module  142  and is processed. Operation proceeds from step  1512  to step  1514 . In step  1514 , a first section of a first audio publication provided by presentation manager  138  or the connected third-party module  142  is selected for presentation, and operation proceeds to decision block  1516 . In decision block  1516 , it is determined whether network connectivity exists. If network connectivity is determined to be present, operation proceeds to step  1518 , and otherwise proceeds to step  1520 . In step  1518 , the local presentation system runtime state (see section D.2) is synchronized with the runtime state stored remotely in subscriber database  122 , and operation proceeds to step  1520 . In step  1520 , the current application runtime state (e.g., the presentation device executive logic  1002  runtime state) is initialized to the current presentation system runtime state, which may cause a new section and/or audio publication to be selected. Operation proceeds from step  1520  to step  1522 . Flowchart  1500  returns to flowchart  1400  at step  1522 , after both of the first and second execution paths of flowchart  1500  have completed and rejoined. 
     D.14. Presentation Device Executive “Handle Command” Process 
       FIGS. 16A-16D  depict a flowchart  1600  for an example “Handle Command” process, according to an example embodiment. Flowchart  1600  may be performed by presentation device executive logic  1002  of  FIG. 10 , for example. In an embodiment, flowchart  1600  may be performed in processes  1406  and  1486  of flowchart  1400  ( FIGS. 14A-14B ). Flowchart  1600  is entered at entry step  1601 . Subsequent to entry step  1601 , a valid received command (e.g., see Table 6 below) is determined by evaluating decision blocks  1602 - 1619 . Each of decision blocks  1602 - 1619  corresponds to a particular command that may be received. If a valid command is received, the corresponding branch node is selected, and the command is processed. After the command has been processed, operation proceeds either to step  1620  ( FIG. 16D ), from which flowchart  1600  returns to flowchart  1400 , or proceeds to a particular exit point (e.g., one of exit points  1624 ,  1626 ,  1629 ,  1633 ,  1635 ,  1649 , or  1666 ), from which flowchart  1600  returns to flowchart  1400  at a corresponding entry point. 
     Throughout this section, it is assumed that an audio content item is playing to a subscriber when flowchart  1600  is entered at entry step  1601 . Operation proceeds from entry step  1601  to step  1621 . In step  1621 , playback of the current audio content item may be paused. At this point, a subscriber-issued command may be received and processed according to flowchart  1600 . If a command is received from the subscriber and no audio content item is playing, step  1621  may be skipped. Operation proceeds from step  1621  to decision blocks  1602 - 1619 , which determine whether a command corresponding to one of decision blocks  1602 - 1619  has been issued. When a command corresponding to one of decision blocks  1602 - 1619  is determined to be received, the command is processed as described below. If such a command is not determined to be received, operation proceeds to step  1620 . 
     Skip  1602 : A skip command may be determined to be received at decision block  1602 . In such case, operation proceeds to step  1622 . In step  1622 , the audio content item enters the “skipped” state, and in step  1623 , the audio content item is added to the “Skipped Content” section (see section D.7). Operation proceeds to “Next ACI” exit point  1624 , and flowchart  1400  is reentered at decision block  1432  (by proceeding from “Next ACI” exit point  1624  of  FIG. 16A  to “Next ACI” entry point  1474  of  FIG. 14A ). 
     Discard  1603 : A discard command may be determined to be received at decision block  1603 . In such case, operation proceeds to step  1625 . In step  1625 , the audio content item enters the “discarded” state. Operation proceeds to exit point  1626 , and flowchart  1400  is reentered at decision block  1432  (by proceeding from next ACI exit point  1626  of  FIG. 16A  to “Next ACI” entry point  1474  of  FIG. 14A ). 
     Previous Audio Content Item  1604 : A previous audio content item command may be determined to be received at decision block  1604 . In such case, operation proceeds to step  1627 . In step  1627 , the previously “played,” “skipped,” or “discarded” audio content item is fetched, and in step  1628 , the audio content item state is initialized to the “unhandled” state. Operation proceeds to exit point  1629 , and flowchart  1400  is reentered to begin the first and second execution paths subsequent to step  1456  (by proceeding from “Play ACT” exit point  1629  of  FIG. 16A  to “Play ACT” entry point  1490  of  FIG. 14B ). 
     Change Audio Publication  1605 : A change audio publication command may be determined to be received at decision block  1605 . In such case, operation proceeds to step  1630 . In step  1630 , a subscriber&#39;s desired audio publication is selected. In step  1631 , the first section of the selected audio publication with at least one unhandled or skipped audio content item is selected. In step  1632 , the selected audio publication is announced to the subscriber. Operation proceeds to “Change Section” exit point  1633 , and flowchart  1400  is reentered at decision block  1422  (by proceeding from “Change Section” exit point  1633  of  FIG. 16A  to “Change Section” entry point  1420  of  FIG. 14A ). 
     Change Section  1606 : A change section command may be determined to be received at decision block  1606 . In such case, operation proceeds to step  1634 . In step  1634 , a subscriber&#39;s desired audio publication section is selected. Operation proceeds to “Change Section” exit point  1635 , and flowchart  1400  is reentered at decision block  1422  (by proceeding from “Change Section” exit point  1635  of  FIG. 16A  to “Change Section” entry point  1420  of  FIG. 14A ). 
     Search  1607 : A search command may be determined to be received at decision block  1607  ( FIG. 16B ). In such case, operation proceeds to step  1636 . In step  1636 , a search expression is entered/generated by a subscriber, such as by voice control interface  1020 , by directly entering text (see section D.5), etc., and operation proceeds to step  1637 . In step  1637 , search results containing any matching audio content items are retrieved and presented to the user of the presentation device either aurally (e.g., by using text-to-speech engine  1046 ), textually, or in both formats, and step  1638  is performed. In step  1638 , matching audio content items that are available for immediate presentation are added to the “Search Results” audio publication section (see section D.7). Operation proceeds from step  1638  to decision block  1639 . In decision block  1639 , it is determined whether any of the matching audio content items retrieved in step  1637  are selected by the subscriber. If it is determined that none of the search results retrieved in step  1637  are selected by the subscriber, or if no audio content items matched the search expression created in step  1636 , playback of the current audio content item is resumed in step  1640 . Following step  1640 , flowchart  1600  returns to flowchart  1400  from step  1641 . If it is determined in decision block  1639  that an audio content item search result is selected by the subscriber, operation proceeds to decision block  1642 . In decision block  1642  it is determined whether the current audio publication is to be switched/changed. If it is determined that the current audio publication needs to be switched, operation proceeds to step  1643 , and if not, operation proceeds to decision block  1645 . In step  1643 , a new audio publication is selected, and in step  1644 , the new audio publication is announced to the subscriber. Operation proceeds from step  1644  to decision block  1645 . In decision block  1645 , it is determined whether the current section is to be switched/changed. If it is determined that the current section is to be switched, operation proceeds to step  1646 , and if not, operation proceeds to step  1648 . In step  1646 , a new section is selected, and in step  1647 , the new section is announced to the subscriber. Operation proceeds from step  1647  to step  1648 . In step  1648 , the current audio content item is switched to the selected audio content item search result. Operation proceeds to exit point  1649 , and flowchart  1400  is reentered to begin the first and second execution paths subsequent to step  1456  (by proceeding from “Play ACI” exit point  1649  of  FIG. 16B  to “Play ACI” entry point  1490  of  FIG. 14B ). 
     Set Preferences  1608 : A set preferences command may be determined to be received at decision block  1608  ( FIG. 16C ). In such case, operation proceeds to step  1650 . In step  1650 , the presentation system runtime preferences may be handled (see section D.4), such as by presenting a sequence of speech prompts to a subscriber, by using a graphical menu interface (if supported by presentation device  140 ), and/or using another technique. After the runtime preferences have been set by a subscriber in step  1650 , operation proceeds to step  1651 . In step  1651 , playback of the current audio content item is resumed, and operation proceeds to step  1620 . 
     List Audio Publications or Sections  1609 : A list audio publications or sections command may be determined to be received at decision block  1609 . In such case, operation proceeds to step  1652 . In step  1652 , depending on the received command, either a list of the available audio publications (for a received list audio publications command) or a list of the audio publication sections contained in the current audio publication (for a received list sections command) is announced to a subscriber, such as by using prerecorded speech prompts, electronic text-to-speech (e.g., using text-to-speech engine  1046 ), or another technique. Optionally, the list of audio publications or sections may be presented visually, if supported by presentation device  140 . Operation proceeds to decision block  1653 . In decision block  1653 , a subscriber is enabled to preempt (e.g., pause, restart, and/or presentation of the listing announcement. After playback of the listing announcement has completed in step  1652 , playback of the current audio content item is resumed in step  1654 , and operation proceeds to step  1620 . 
     Get Status  1610 : A get status command may be determined to be received at decision block  1610 . In such case, operation proceeds to step  1655 . In step  1655 , a status report is generated, and in step  1656 , the status report is played to a subscriber, such as by using electronic text-to-speech (e.g., using text-to-speech engine  1046 ). Optionally, the status report may be presented visually, if supported by presentation device  140 . Operation proceeds to a decision block  1657 . In decision block  1657 , a subscriber is enabled to preempt playback of the status report. When playback of the status report has completed in step  1656 , playback of the current audio content item is resumed in step  1658 , and operation proceeds to step  1620 . 
     Get Help  1611 : A get help command may be determined to be received at decision block  1611 . In such case, operation proceeds to step  1659 . In step  1659 , contextual help is presented to a subscriber (e.g., in the form of a dialog), such as by using prerecorded speech prompts or electronic text-to-speech (e.g., using text-to-speech engine  1046 ). Optionally, help may be presented visually, if supported by presentation device  140 . Operation proceeds to decision block  1660 . In decision block  1660 , a subscriber is enabled to preempt playback of the contextual help. When playback of the contextual help has completed in step  1659 , playback of the current audio content item is resumed in step  1661 , and operation proceeds to step  1620 . 
     Next/Previous Paragraph  1612 : A next/previous paragraph command may be determined to be received at decision block  1612 . In such case, operation proceeds to step  1662 . In step  1662 , depending on the command issued, playback either skips forward to a next paragraph or backward to the beginning of a previous (or the current) paragraph within the current audio content item. Playback of the current audio content item is resumed in step  1663 , and operation proceeds to step  1620 . 
     Pause  1613 : A pause command may be determined to be received at decision block  1613 . Because audio content item playback is paused in step  1621 , operation proceeds to step  1620 . 
     Resume  1614 : A resume command may be determined to be received at decision block  1614 . In such case, operation proceeds to step  1664 . In step  1664 , playback of the current audio content item is resumed, and operation proceeds to a decision block  1665 . In decision block  1665 , it is determined whether this is the first “resume” command received from the subscriber since application startup at step  1402  ( FIG. 14A ). If it is determined to be the first resume command, operation proceeds to exit point  1666 , and flowchart  1400  is reentered at decision block  1422  (by proceeding from “Change Section” exit point  1666  of  FIG. 16C  to “Change Section” entry point  1420  of  FIG. 14A ). If it is determined not to be the first resume command, operation proceeds to step  1620 . 
     Tag Audio Content Item or Advertisement  1615 : A tag audio content item or advertisement command may be determined to be received at decision block  1615 . In such case, operation proceeds to step  1667 . In step  1667 , the audio content item&#39;s or advertisement&#39;s “tagged” status flag is alternately set or cleared, and in step  1668 , a speech prompt is played to confirm the current “tagged” status. Playback of the current audio content item (or advertisement) is resumed in step  1669 , and operation proceeds to step  1620 . 
     Track Audio Content Item  1616 : A track audio content item command may be determined to be received at decision block  1616 . In such case, operation proceeds to step  1670 . In step  1670 , the audio content item&#39;s “tracked” status flag is alternately set or cleared, and in step  1671 , a speech prompt is played to confirm the current “tracked” status. Playback of the current audio content item is resumed in step  1672 , and operation proceeds to step  1620 . 
     Enable/Disable Voice Control  1617 : An enable/disable voice control command may be determined to be received at decision block  1617 . In such case, operation proceeds to step  1673 . In step  1673 , voice control is alternately enabled or disabled, and in step  1674 , a speech prompt is played to the subscriber to confirm the current voice control state. Playback of the current audio content item is resumed in step  1675 , and operation proceeds to step  1620 . 
     Undo  1618 : An undo command may be determined to be received at decision block  1618  ( FIG. 16D ). In such case, operation proceeds to decision block  1676 . Decision block  1676  determines whether the previous completed command can be undone. If it is determined that the previously completed command can be undone, operation proceeds to step  1677 , and if not, operation proceeds to step  1679 . In step  1677 , the previous completed command is undone, and operation proceeds to step  1678 . In step  1678 , the undone command is added to a redo stack, and operation proceeds to step  1620 . In step  1679 , playback of the current audio content item is resumed, and operation proceeds to step  1620 . 
     Redo  1619 : A redo command may be determined to be received at decision block  1619 . In such case, operation proceeds to decision block  1680 . Decision block  1680  determines whether there are any previously undone commands that can be redone. If it is determined that there are previously undone commands that can be redone, operation proceeds to step  1681 , and if not, operation proceeds to step  1682 . In step  1681 , the last undone command is redone, and operation proceeds to step  1620 . In step  1682 , playback of the current audio content item is resumed, and operation proceeds to step  1620 . 
     D.15. Presentation Device Executive “Handle Title Mode” Process 
       FIG. 17  depicts a flowchart  1700  for an example “Handle Title Mode” process, according to an example embodiment. Flowchart  1700  may be performed by presentation device executive logic  1002  of  FIG. 10 , for example. In an embodiment, flowchart  1700  may be performed in process  1466  of flowchart  1400  ( FIG. 14B ). Flowchart  1700  may be entered when title mode (see section D.1) is active and the title segment of an audio content item has finished being played by the presentation device (see  FIG. 14 ). A value returned by flowchart  1700  indicates whether the summary segment of the audio content item is to be played. For example, if the return value is “true,” playback of the summary segment is enabled. If the return value is “false,” playback of the summary segment is not enabled. 
     Flowchart  1700  is entered at entry step  1702 , and operation proceeds to a step  1704 . In step  1704 , the return value for flowchart  1700  is initialized to “false,” and operation proceeds to decision block  1706 . In decision block  1706 , it is determined whether speech prompts are enabled in the runtime preferences. If it is determined that speech prompts are enabled, operation proceeds to step  1710 , and if not, operation proceeds to first and second execution branches, which are performed concurrently. In step  1710 , speech prompt  1708  is played to ask the subscriber whether the summary segment should be played, and operation proceeds to the first and second execution branches. 
     In the first (e.g., left-hand in  FIG. 17 ) execution path, step  1712  is performed, which temporarily suspends execution of the execution path for a predetermined period of time (e.g., 1-2 seconds) and enables a “Play More” command to be received from a subscriber. After the wait delay has expired, operation proceeds to step  1718 . In the second (e.g., right-hand in  FIG. 17 ) execution path, decision block  1714  is performed, where the “Play More” command is awaited. When decision block  1714  determines that the “Play More” command is received, operation proceeds to step  1716 . In step  1716 , the return value of flowchart  1700  is set to “true,” and operation proceeds to step  1718 . If decision block  1714  determines that the “Play More” command is not received by the time the wait delay of step  1712  expires, execution of the right-hand execution path terminates, and operation proceeds from step  1718  back to flowchart  1400 . 
     D.16. Presentation Device Executive “Handle Summary Mode” Process 
       FIG. 18  depicts a flowchart  1800  for an example “Handle Summary Mode” process, according to an example embodiment. Flowchart  1800  may be performed by presentation device executive logic  1002  of  FIG. 10 , for example. In an embodiment, flowchart  1800  may be performed in process  1478  of flowchart  1400  ( FIG. 14B ). Flowchart  1800  may be performed when either title mode or summary mode is active and a summary segment of an audio content item has finished playing (see  FIG. 14B ). A value returned by flowchart  1800  indicates whether the story body segment of the audio content item is to be played. For example, if the return value is “true,” playback of the story body segment is enabled. If the return value is “false,” playback of the story body segment is not enabled. 
     Flowchart  1800  is entered at entry step  1802 , and operation proceeds to step  1804 . In step  1804 , the return value of flowchart  1800  is initialized to “false,” and operation proceeds to decision block  1806 . In decision block  1806 , it is determined whether speech prompts are enabled in the runtime preferences. If it is determined that speech prompts are enabled in the runtime preferences, operation proceeds to step  1810 , and if not, operation proceeds to first and second execution branches, which are performed concurrently. In step  1810 , a speech prompt  1808  is played to ask the subscriber whether the story body segment should be played, and operation proceeds to the first and second execution branches. 
     In the first (e.g., left-hand in  FIG. 18 ) execution path, step  1812  is performed, which temporarily suspends execution of the execution path for a predetermined period of time (e.g., 1-2 seconds), and enables the “Play More” command to be received from a subscriber. After the wait delay has expired, operation proceeds to step  1818 . In the second (e.g., right-hand in  FIG. 18 ) execution path, a decision block  1814  is performed, where the “Play More” command is awaited. When decision block  1814  determines that the “Play More” command is received, operation proceeds to step  1816 . In step  1816 , the return value of flowchart  1800  is set to “true,” and operation proceeds to step  1818 . If decision block  1814  determines that the “Play More” command is not received by the time the wait delay of step  1812  expires, execution of the right-hand path terminates, and operation proceeds from step  1818  back to flowchart  1400 . 
     D.17. Presentation Device Executive “Handle Played Audio Content Item” Process 
       FIG. 19  depicts a flowchart  1900  for an example “Handle Played Audio Content Item” process, according to an example embodiment. Flowchart  1900  may be performed by presentation device executive logic  1002  of  FIG. 10 , for example. In an embodiment, flowchart  1900  may be performed in process  1484  of flowchart  1400  ( FIG. 14B ). 
     Flowchart  1900  may be entered when a story body segment of an audio content item has finished playing (see  FIG. 14B ). Flowchart  1900  enables a subscriber to set the “tracked” and/or “tagged” status flags of the played audio content item (see section D.2). 
     Flowchart  1900  is entered at entry step  1902 , and operation proceeds to step  1904 . In step  1904 , the played audio content item is indicated as having entered the “played” state, and operation proceeds to step  1908 . In step  1908 , a speech prompt  1906  is played to the subscriber announcing that presentation of the current audio content item has completed, and operation proceeds to decision block  1910 . In decision block  1910 , it is determined whether speech prompts are enabled in the runtime preferences. If it is determined that speech prompts are enabled, operation proceeds to step  1916 , and if not, operation proceeds to step  1912 . In step  1912 , execution of flowchart  1900  is temporarily suspended for a predetermined period of time (e.g., 1-2 seconds), and operation proceeds to step  1930 . In step  1916 , a speech prompt  1914  is played to the subscriber asking whether the audio content item should be tagged, and operation proceeds to decision block  1918 . In decision block  1918 , it is determined whether the subscriber indicated that the audio content item should be tagged. If the subscriber indicated that the audio content item should be tagged, operation proceeds to step  1920 , and if not, operation proceeds to step  1924 . In step  1920 , the audio content item&#39;s “tagged” status flag is set, and operation proceeds to step  1924 . In step  1924 , a speech prompt  1922  is played to the subscriber asking whether the audio content item should be tracked, and operation proceeds to decision block  1926 . In decision block  1926 , it is determined whether the subscriber indicated that the audio content item should be tracked. If it is determined that the subscriber indicated that the audio content item should be tracked, operation proceeds to step  1928 , and if not, operation proceeds to step  1930 . In step  1928 , the audio content item&#39;s “tracked” status flag is set, and operation proceeds to step  1930 . In step  1930 , operation proceeds back to flowchart  1400 . 
     Example Commands 
     Table 6 shown below lists a number of commands that may be received from a user by a presentation device to select audio publications, to cause audio publications to be played, to navigate among and within audio publications, to modify the playing of audio publications, and to enable further functions. The commands shown in Table 6 are provided for purposes of illustration, and are not intended to be limiting. Additional and/or alternative commands may also be enabled in embodiments. Furthermore, each command may be provided by a subscriber in various ways, including by voice command, by manual entry (e.g., by pushing physical or virtual buttons, etc.), and/or by further techniques. For voice commands, optional command words are enclosed in brackets: 
     
       
         
           
               
             
               
                 TABLE 6 
               
             
            
               
                   
               
               
                 Presentation system commands and equivalent voice control commands. 
               
            
           
           
               
               
               
               
            
               
                   
                 Command 
                 Voice Commands 
                 Purpose 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                 Navigation 
                 Previous 
                 previous 
                 Fetches the previous audio 
               
               
                   
                   
                 [go] back 
                 content item 
               
               
                   
                 Previous 
                 previous 
                 Navigates to the previous 
               
               
                   
                 paragraph 
                 paragraph 
                 paragraph in an audio content 
               
               
                   
                   
                   
                 item 
               
               
                   
                 Next 
                 next paragraph 
                 Advances to the next paragraph 
               
               
                   
                 paragraph 
                   
                 in an audio content item 
               
               
                   
                 Change section 
                 [goto] 
                 Jumps to section name 
               
               
                   
                   
                 section&lt;name&gt; 
               
               
                   
                 Change 
                 [goto] [audio] 
                 Jumps to audio publication name 
               
               
                   
                 audio 
                 publication 
               
               
                   
                 publication 
                 &lt;name&gt; 
               
               
                   
                 Search 
                 search &lt;keyword 
                 Searches for audio content items 
               
               
                   
                   
                 expression&gt; 
                 that match the provided keyword 
               
               
                   
                   
                   
                 expression 
               
               
                 Control 
                 Play 
                 play 
                 Starts/restarts playback 
               
               
                   
                   
                 start 
               
               
                   
                   
                 resume 
               
               
                   
                 Play more 
                 more 
                 Plays the audio content item&#39;s 
               
               
                   
                   
                   
                 summary segment (title mode), 
               
               
                   
                   
                   
                 or the story body segment 
               
               
                   
                   
                   
                 (summary mode) 
               
               
                   
                 Skip 
                 skip 
                 Temporarily skips an audio 
               
               
                   
                   
                 next 
                 content item and adds it to the 
               
               
                   
                   
                   
                 “Skipped Content” section 
               
               
                   
                 Discard 
                 discard 
                 Discards the current audio 
               
               
                   
                   
                   
                 content item and moves to the 
               
               
                   
                   
                   
                 next audio content item 
               
               
                   
                 Stop/Pause 
                 stop 
                 Stops playback 
               
               
                   
                   
                 pause 
               
               
                   
                 Undo 
                 undo 
                 Undo the last operation 
               
               
                   
                 Redo 
                 redo 
                 Redo the last “undo” operation 
               
               
                 Customization 
                 Track audio 
                 track 
                 Sets/clears the audio content 
               
               
                   
                 content item 
                   
                 item&#39;s “tracked” flag 
               
               
                   
                 Tag audio 
                 tag 
                 Sets/clears the audio content 
               
               
                   
                 content item or 
                   
                 item&#39;s or advertisement&#39;s 
               
               
                   
                 advertisement 
                   
                 “tagged” flag 
               
               
                   
                 Switch mode 
                 switch to mode 
                 Switches the current operating 
               
               
                   
                   
                   
                 mode (title, summary, or full 
               
               
                   
                   
                   
                 story mode) 
               
               
                   
                 Set playback 
                 play new [first] 
                 Sets the playback order so that 
               
               
                   
                 order 
                 play old [first] 
                 either newer or older audio 
               
               
                   
                   
                   
                 content items are played first 
               
               
                   
                 Set preferences 
                 [set] preferences 
                 Enables runtime preferences to 
               
               
                   
                   
                   
                 be configured 
               
               
                   
                 Enable/disable 
                 start (stop) 
                 Enables/disables the speech 
               
               
                   
                 voice control 
                 listening 
                 recognition module 
               
               
                 Help 
                 Get help 
                 help 
                 Access help 
               
               
                   
                 Get status 
                 [get] status 
                 Get a real-time status report 
               
               
                   
                 List 
                 list [audio] 
                 Lists available audio publications 
               
               
                   
                   
                 publications 
                 or sections 
               
               
                   
                   
                 list sections 
               
               
                   
               
            
           
         
       
     
     Example Interactive Audio Publication Presentation Embodiments 
     Various embodiments for an interactive audio publication generation and presentation are described in the sections above.  FIG. 20  shows a flowchart  2000  for audio publication generation, customization, distribution, and presentation, according to example embodiments. Flowchart  2000  may be performed by embodiments described above, including creation system  102 , customization &amp; distribution system  110 , subscriber portal  124 , and/or presentation system  136  of interactive audio publication system  100  of  FIG. 1 , and/or by the further embodiments and sub-features of these systems/portals described elsewhere herein and shown in the figures (e.g., presentation device  140 , etc.). Further structural and operational embodiments will be apparent to persons skilled in the relevant art(s) based on the discussion regarding flowchart  2000 . Embodiments for performing each of the steps of flowchart  2000  are shown in  FIGS. 1-13  and  FIGS. 14A-19  (e.g., flowcharts  1400 ,  1500 ,  1600 ,  1700 ,  1800 , and  1900 ) and described above. Flowchart  2000  is described as follows. 
     Referring to  FIG. 20 , at step  2002 , a plurality of content items is received that includes at least one text-based content item or speech-based content item. For example, as described above, creation system  102  of  FIG. 1  may receive a plurality of content items that includes one or more text-based content items and/or speech-based content items. 
     In step  2004 , the received plurality of content items is converted into corresponding audio content items that each includes digital audio data corresponding to a spoken representation of a corresponding text-based content item or speech-based content item, and audio content item metadata indicating a structure of the included digital audio data. For example, as described above, audio content item creation module  104  of  FIGS. 1 ,  2 A, and/or  2 B may be configured to convert content items into corresponding audio content items that each includes digital audio data corresponding to a spoken representation of a corresponding text-based content item or speech-based content item and audio content item metadata. For example, system  200  of  FIG. 2A  is an example of audio content item creation module  104  for generating audio content items  242  from text-based content items  204 , and system  250  of  FIG. 2B  is an example of audio content item creation module  104  for generating audio content items  294  from speech-based content items  254 . Audio content item metadata creation modules  236  ( FIG. 2A) and 288  ( FIG. 2B ) are example modules for generating audio content item metadata. As described above, audio content item metadata may be generated that includes one or more markers designating boundaries of a title segment, a summary segment, and a story body segment of an audio content item in the form of time-based and/or word-based boundaries, references to files, etc. Additionally, audio content item metadata may contain scheduling details used to present associated visual content items and/or advertisements, as well as file references to one or more visual content item and/or advertisement files. 
     In step  2006 , an audio publication is assembled from one or more of the audio content items, the audio publication being organized into one or more sections. For example, as described above, audio publication creation module  106  of  FIG. 1  may be configured to assemble an audio publication from one or more audio content items. Example embodiments for audio publication module  106  are shown in  FIGS. 3A and 3B , and described above. 
     In step  2008 , audio publication metadata is generated that defines a structure of the audio publication. For example, as described above, audio publication assembly module  324  of  FIG. 3A  is configured to generate audio publication metadata for audio publications. Furthermore, ad hoc audio publication creation module  362  receives analyzed metadata details  360  and generates an ad hoc audio publication  368  that includes audio publication metadata. 
     In step  2010 , the audio publication is customized for at least one user, using one or more subscriber-defined custom audio publication templates. An audio publication may be optionally customized For example, as described above, audio publication customization module  112  of customization &amp; distribution system  110  may transform audio publications  118  into custom audio publications  120 . Embodiments of audio publication customization module  112  are shown in  FIGS. 5A-5D . 
     In step  2012 , the audio publication is distributed to a user for interactive presentation, the distributed audio publication including the audio publication metadata and the one or more audio content items. For example, as described above, customization &amp; distribution system  110  of  FIG. 1  is configured to enable audio publications to be distributed for interactive presentation, such as by presentation system  136 . The audio publication may be presented by a presentation system in various ways, including according to one or more of the flowcharts of  FIGS. 14A-19 . 
     In step  2014 , accounts and profile settings for users, custom audio publication templates, and access to audio publications and audio content items are managed. For example, as described above, subscriber portal  124  is configured to enable users to manage corresponding accounts and profile settings, to enable users to configure custom audio publication templates, and to enable users to access audio publications and audio content items. 
     Further Example Embodiments 
     Features shown in the figures and described herein may be implemented in various ways. For example, the modules, engines, and further features shown in the figures and described above may be implemented in hardware, software, firmware, or any combination thereof. For example, such modules, engines, and further features may be implemented as computer program code configured to be executed in one or more processors. Alternatively, such modules, engines, and further features may be implemented as hardware logic/electrical circuitry. 
     The search engines shown in the figures and described above may be implemented in hardware, software, firmware, or any combination thereof. Such search engines may use a ranking or relevance function, or other ranking/relevance functionality, to rank corresponding items/objects in an order of relevance (e.g., to a user), as would be known to persons skilled in the relevant art(s). 
     The databases shown in the figures and described above may be embodied in various ways, including as a data structure such as one or more text files, one or more tables, one or more data arrays, one or more databases, etc., capable of containing the corresponding data, items, objects, etc. Such databases may be stored in one or more of any type of storage mechanism, including a magnetic disc (e.g., in a hard disk drive), an optical disc (e.g., in an optical disk drive), a magnetic tape (e.g., in a tape drive), a memory device such as a RAM device, a ROM device, etc., and/or any other suitable type of storage medium. 
       FIG. 21  depicts an exemplary implementation of an electronic device  2100  in which embodiments of the present invention may be implemented. Electronic device  2100  may be a general-purpose computing device in the form of a conventional personal computer, a work station, a mobile computer, a handheld music player (e.g., an Apple® iPod®, etc.), a mobile phone or smart phone (e.g., an Apple® iPhone®, etc.) or electronic device  2100  may be a special purpose computing device. The description of electronic device  2100  provided herein is provided for purposes of illustration, and is not intended to be limiting. Embodiments of the present invention may be implemented in further types of electronic devices, as would be known to persons skilled in the relevant art(s). 
     As shown in  FIG. 21 , electronic device  2100  includes a processing unit  2102 , a system memory  2104 , and a bus  2106  that couples various system components including system memory  2104  to processing unit  2102 . Bus  2106  represents one or more of any of several types of bus structures, including a memory bus or memory controller, a peripheral bus, an accelerated graphics port, and a processor or local bus using any of a variety of bus architectures. System memory  2104  includes read only memory (ROM)  2108  and random access memory (RAM)  2110 . A basic input/output system  2112  (BIOS) is stored in ROM  2108 . 
     Electronic device  2100  also has one or more of the following drives: a hard disk drive  2114  for reading from and writing to a hard disk, a magnetic disk drive  2116  for reading from or writing to a removable magnetic disk  2118 , and an optical disk drive  2120  for reading from or writing to a removable optical disk  2122  such as a CD ROM, DVD ROM, or other optical media. Hard disk drive  2114 , magnetic disk drive  2116 , and optical disk drive  2120  are connected to bus  2106  by a hard disk drive interface  2124 , a magnetic disk drive interface  2126 , and an optical drive interface  2128 , respectively. The drives and their associated computer-readable media provide nonvolatile storage of computer-readable instructions, data structures, program modules and other data for the computer. Although a hard disk, a removable magnetic disk and a removable optical disk are described, other types of computer-readable media can be used to store data, such as flash memory cards, digital video disks, random access memories (RAMs), read only memories (ROM), and the like. 
     A number of program modules may be stored on the hard disk, magnetic disk, optical disk, ROM, or RAM. These programs include an operating system  2130 , one or more application programs  2132 , other program modules  2134 , and program data  2136 . Application programs  2132  or program modules  2134  may include, for example, computer program logic for implementing one or more of the elements shown in  FIGS. 1-13 , and any one or more steps/decision blocks/processes shown in the flowcharts of  FIGS. 14A-19 , as described above. 
     A user may enter commands and information into the electronic device  2100  through input devices such as keyboard  2138  and pointing device  2140 . Other input devices (not shown) may include a microphone, touchscreen, control buttons, joystick, game pad, satellite dish, scanner, or the like. These and other input devices are often connected to the processing unit  2102  through a serial port interface  2142  that is coupled to bus  2106 , but may be connected by other interfaces, such as a parallel port, game port, or a universal serial bus (USB). Keyboard  2138  and other input devices may be external to electronic device  2100  (e.g., when electronic device  2100  is a desktop computer) or may be mounted in a surface of electronic device  2100  (e.g., when electronic device  2100  is a mobile device, such as a laptop computer, handheld computing device, mobile phone, portable music player, etc.). 
     A display  2144  is also connected to bus  2106  via an interface, such as a video adapter  2146 . In addition to the monitor, electronic device  2100  may include other peripheral output devices (not shown) such as speakers and printers. Display  2144  may be external to electronic device  2100  or may be mounted in a surface of electronic device  2100 . One or more loudspeakers may be connected to bus  2106  via an interface, such as an audio adaptor of electronic device  2100 . The loudspeakers may be built into a body of electronic device  2100 , or may be external loudspeakers, such as a pair of headphones or external speakers connected to electronic device  2100 . 
     Electronic device  2100  may be connected to a network  2148  (e.g., the Internet, a telecommunications network, a cellular network, etc.) through a network interface or adapter  2150 , a modem  2152 , or other means for establishing communications over the network. Modem  2152 , which may be internal or external, is connected to bus  2106  via serial port interface  2142 . 
     As used herein, the terms “computer program medium” and “computer-readable medium” are used to generally refer to media such as the hard disk associated with hard disk drive  2114 , removable magnetic disk  2118 , removable optical disk  2122 , as well as other media such as flash memory cards, digital video disks, random access memories (RAMs), read only memories (ROM), and the like. 
     As noted above, computer programs and modules (including application programs  2132  and other program modules  2134 ) may be stored on the hard disk, magnetic disk, optical disk, ROM, or RAM. Such computer programs may also be received via network interface  2150  or serial port interface  2142 . Such computer programs, when executed or loaded by an application, enable electronic device  2100  to implement features of embodiments of the present invention discussed herein. Accordingly, such computer programs represent controllers of the electronic device  2100 . 
     The invention is also directed to computer program products comprising software stored on any computer useable medium. Such software, when executed in one or more data processing devices, causes a data processing device(s) to operate as described herein. Embodiments of the present invention employ any computer-useable or computer-readable medium, known now or in the future. Examples of computer-readable mediums include, but are not limited to storage devices such as RAM, hard drives, floppy disks, CD ROMs, DVD ROMs, zip disks, tapes, magnetic storage devices, optical storage devices, MEMs, nanotechnology-based storage devices, and the like. 
     Example Advantages 
     The interactive audio publication system embodiments described herein includes advantages over conventional techniques. Embodiments of the interactive audio publication system may include one or more of the following advantages, including: 
     Providing a complete end-to-end system that handles the generation, customization, distribution, and presentation of an interactive audio publication; 
     Enabling both text and speech-based content (e.g., podcasts, etc.) to be transformed into interactive “audio content items,” that are further organized into navigable audio publications; 
     Featuring a novel presentation system that includes an apparatus that utilizes subscriber input to present audio content interactively and dynamically; 
     Enabling audio content items to appear in multiple sections within an audio publication, while ensuring that previously presented audio content items are not repeated to subscribers; 
     Enabling subscribers to customize preexisting audio publications and to generate new custom audio publications according to their preferences and interests; 
     Enabling sequencing of visual content (e.g., images and movies) for display to subscribers during presentation of an audio content item; 
     Enabling targeted audio and/or visual advertisements to be selected by a publisher and delivered to subscribers, with the ability to provide publishers with playback confirmation; and 
     Providing automatic adaptation of audio publications for playback on various presentation device embodiments. 
     Embodiments of the presentation device may provide one or more of the following advantages over conventional implementations, including: 
     a robust hands-free speech recognition interface enabling subscribers to interact with audio publications using simple voice commands; 
     an intuitive button interface enabling subscribers to navigate interactive audio publications easily and discreetly; 
     an ability for a subscriber to choose the desired level of presentation detail on-the-fly for selected audio content (e.g., title only, title and summary, full story, etc.); 
     nonlinear subscriber navigation through interactive audio publications and audio content items, with the ability to navigate between available audio publications and audio publication sections, and to skip forward or backward by whole paragraphs of text; 
     automatic monitoring and reporting of a subscriber&#39;s progress through the audio publication, ensuring that previously played audio content items are not replayed; 
     an ability for a subscriber to prioritize content and temporarily skip audio content items for playback at a later time; 
     on-demand subscriber audio content item “tracking” such that new audio content items with high relevance are added to a special “Tracked Content” section automatically over time (i.e., a work day, week, month, etc.); 
     audio content item “tagging” and sharing via a subscriber&#39;s email or online social networking sites; 
     advertisement “tagging,” enabling review of presented advertisements at a later time; 
     audio content item searching via subscriber-typed or subscriber-dictated keyword search expressions; 
     a preferences mode enabling subscribers to configure their presentation system runtime preferences; and 
     speech prompts that assist the subscriber if they want help. 
     Example Embodiments 
     A method for presenting an interactive audio publication to a user may include: 
     receiving a plurality of content items that includes at least one text-based content item or speech-based content item; converting the received plurality of content items into corresponding audio content items that each include digital audio data corresponding to a spoken representation of a corresponding text-based content item or speech-based content item, and audio content item metadata indicating a structure of the included digital audio data, the audio content item metadata including a plurality of markers designating boundaries of a title segment, a summary segment, and a story body segment of an audio content item; assembling an audio publication from one or more of the audio content items, the audio publication being organized into one or more sections; generating audio publication metadata that defines a structure of the audio publication, said generating comprising customizing the audio publication metadata for at least one user; and distributing the audio publication to a user for interactive presentation, the distributed audio publication including the audio publication metadata and the one or more audio content items. 
     The converting may include: determining markers that designate word, sentence, and paragraph boundaries in a received content item, and including the determined markers in the audio content item metadata corresponding to the received content item. 
     The determining may include: using an automatic speech recognition (ASR) system to locate the word, sentence, and paragraph boundary markers within a received content item. 
     The converting may include: performing said converting prior to said assembling, after said assembling and prior to the interactive presentation, or in a plurality of stages in which one or more portions of a first audio content item are generated prior to said assembling and remaining portions of the first audio content item are generated after said assembling and prior to the interactive presentation. 
     The method may further include: enabling a user to indicate a summary segment length by specifying a number of audio content item introductory paragraphs. 
     The converting may further include: using at least one of human voice talent or computerized text-to-speech (TTS) to convert a text-based content item into a corresponding audio content item. 
     The method may further include: selecting one or more visual content items, and embedding scheduling details for display of the selected one or more visual content items during presentation of a corresponding audio content item in audio content item metadata of the corresponding audio content item. 
     The method may further include: enabling a publisher to specify a default ordering of sections within the audio publication, and enabling the publisher to specify a default ordering of audio content items within each section within the audio publication. 
     A single audio content item may be associated with a plurality of audio publication sections. 
     The method may further include: selecting a plurality of prerecorded speech prompts to be played in response to one or more predesignated actions performed by a user during presentation of the audio publication. 
     The method may further include: automatically generating an ad hoc audio publication based a plurality of audio content items received from a content source. 
     The method may further include: enabling a user to define one or more custom audio publication templates, the custom audio publication templates being configured to be used to generate one or more custom audio publications from one or more source audio publications, and the custom audio publication templates including one or more custom sections, such that each custom section contains one or more audio content item assignment rules. 
     The method may further include performing the assignment rule, including: selecting one or more audio content items from one or more of the source audio publications, and assigning the selected one or more audio content items to one or more of the custom sections. 
     The method of claim  12 , may further include performing the assignment rule, including: using a search engine to locate audio content items from one or more of the source audio publications that match a keyword search expression, and adding the matching audio content items to a custom section of the one or more custom sections. 
     The method of claim  12 , may further include performing the assignment rule, including: using a search engine to locate audio content items from one or more of the source audio publications that are relevant to at least one user-designated audio content item, and including the located audio content items in a custom section of the one or more custom sections. 
     The method of claim  1 , may further include: selecting at least one audio and/or visual advertisement, and embedding scheduling details in audio publication metadata or audio content item metadata for the advertisement that is to be provided during presentation of the audio publication prior to or following presentation of the title segment, the summary segment, or the story body segment of an audio content item. 
     The advertisement may be targeted to a user by utilizing information derived from at least one of an audio content item contained in a custom audio publication of the user, a custom audio publication template of the user, an audio content item and advertisement presentation history of the user, or a profile of the user. The history of the user may indicate audio content items and advertisements previously presented to the user, audio content items and advertisements marked “tagged” by the user, and audio content items marked “tracked” by the user. 
     The method may further include: performing advertisement selection on-demand as a result of analyzing the content of a requested audio content item. 
     The method may further include: enabling a user to tag the advertisement so that the user may review the advertisement at a later time. 
     An email may be transmitted to the user as a result of the user tagging the advertisement, the email including at least one of a Web hyperlink to the advertisement, a digital media file associated with the advertisement, or an alternative presentation of the advertisement that includes at least one of text, an image, or audio. 
     The method may further include transferring audio publications that include a plurality of referenced audio content items, visual content items, speech prompts, and advertisements over a data communications network to a presentation system of the user. 
     The method may further include: streaming one or more requested audio publication components over a data communications network to a presentation system of the user for presentation on-demand. 
     The method may further include: issuing a notification to a user when a new or updated audio publication is available for download. 
     The method may further include: transmitting a time-sensitive audio content item over a data communications network to a presentation system of a user for immediate presentation. 
     A system for generating, customizing, distributing, and presenting an interactive audio publication to a user may include: a creation system configured to generate audio content items and audio publications; a customization and distribution system configured to generate one or more custom audio publications according to one or more user-defined custom audio publication templates, and configured to enable distribution of audio publications to a user; a subscriber portal configured to enable users to manage corresponding accounts and profile settings, to enable users to configure custom audio publication templates, and to enable users to access audio publications and audio content items; and a presentation system that includes a presentation manager and a presentation device configured to present one or more interactive audio publications to a user. 
     CONCLUSION 
     While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only and not limitation. It will be understood by those skilled in the relevant art(s) that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined in the appended claims. Accordingly, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.