Patent Publication Number: US-6990677-B1

Title: Application program interfaces for electronic program guide data services

Description:
RELATED APPLICATIONS 
   This application claims the benefit of U.S. Provisional Application Ser. No. 60/125,062, filed Mar. 18, 1999, and entitled “Filtering, Scaling, and Loading of Electronic Guide Data,” which is incorporated herein by reference. This application is also related generally to U.S. patent application Ser. No. 09/527,313 entitled “Systems and Methods for Electronic Program Guide Data Services,” which was filed on the same day as the present application, and is incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   1. The Field of the Invention 
   The present invention relates to electronic program guides (EPGs). More specifically, the present invention relates to application program interfaces enabling EPG data sources and applications using EPG data to interface with EPG services. 
   2. The Prior State of the Art 
   Electronic program guides (EPGs) are designed to permit television viewers as well as Internet webcast viewers to browse and select from television listings which are displayed on a television screen. Before being displayed, the EPG data is downloaded from an EPG source such as a head end or a server to a destination device such as a television, computer or set top box. The EPG source, which may receive EPG data from a number of different EPG data providers, usually consolidates and encrypts the EPG data before transmitting it to the destination device. In conventional systems, the destination device is only capable of receiving EPG data from only one EPG data source, which indicates that the destination device must accept the format of the EPG data provided by the EPG source. More importantly, the EPG data received by a user cannot be tailored to that user&#39;s particular tastes. 
   The ability to retrieve data from a single source in a particular format is not the only drawback of this arrangement. Many destination devices which receive interactive EPG data have limited storage capacity. For this reason, the EPG data downloaded from a data broker or source is typically compressed such that the destination device may store more EPG data in the limited storage space. This selective compression is primarily performed, however, by the EPG data source. This leaves the destination device with the ability to only alter the amount of EPG data downloaded as opposed to the content of the downloaded EPG data. 
   In addition to being unable to alter the content of the downloaded EPG data, a destination device is limited in other significant ways. EPG data from multiple EPG data providers must first be collected and consolidated by a particular EPG source before it is downloaded to a destination device. Destination devices are only capable of receiving EPG data from a single EPG data source. Because destination devices can only receive from one data provider, destination devices are limited to a single data transmission format. 
   Another limitation of current destination devices is that the applications on the destination device that utilize the EPG data must be updated when the EPG data source is changed or altered. Additionally, the applications on the destination device must also be updated when the format of the data source is altered or changed. EPG data is currently being transmitted by various EPG data sources across various transport mediums, but destination devices are unable to take advantage of these sources and mediums because destination devices are limited to one data provider and one format. 
   EPG data typically includes a title, a description and attributes such as closed captioning, rating, and the like. EPG data can be collected from in-band and out of band television signals, HTTP or FTP, TCP/IP sockets or any other communications protocol. The internet, in particular, has become a significant source of EPG data. In fact, EPG data is expanding to include reviews of programs, the names of the actors, and other types and classes of information. Much of this information is readily available, but destination devices are frequently unable to take advantage of that information because, as previously mentioned, the destination devices are limited to a particular EPG data source and a particular EPG data format. 
   It would be an advance in the art for a destination device to be able to receive EPG data from multiple EPG data sources and not be confined to a particular EPG data source or EPG data format. It would also be an advance in the art for a destination device to be able to tailor the content of the EPG data by permitting the EPG data to be scaled both temporally and extensibly. Scaling the EPG data in this manner provides a user, at a minimum, with EPG data that is tailored to the user. 
   SUMMARY OF THE INVENTION 
   The present invention provides EPG services which allows destination devices to overcome present limitations by enabling a destination device to receive EPG data from multiple EPG data sources or providers, including web sites and other conventional EPG data providers. In order to receive EPG data from multiple EPG data sources, a software loader module is loaded or initiated for each EPG data source. The loader module is capable of retrieving EPG data from a particular EPG data source in its native transmission format. The loadable modules interface with an EPG writer module that collects the EPG data from the loader modules and stores the retrieved EPG data locally on the destination device. 
   The interface or EPG writer module comprises a writer application program interface (API) that establishes a standard access point for each loader module. This permits a single EPG writer module to interface with the loader modules of multiple EPG data sources. In this manner, a destination device can receive EPG data from multiple EPG data sources which have different transmission mediums and formats, because a loader module may be created or adapted to each separate EPG data source. The loader modules may receive EPG data in different formats, but all loader modules interface with the EPG writer. 
   Once the EPG data has been locally stored on the destination device by the EPG writer or the EPG writer API, an application may access the EPG data via a controller module which comprises a controller API. The controller API is an interface that allows many different applications to access the locally stored EPG data. The writer API and the controller API also allow applications to be independent of the EPG data sources. This independence allows an application to continue to have access to EPG data even if the EPG source or the format of the EPG data provided by the EPG source is changed. 
   EPG services also introduces significant scalability to the EPG data. Typically, the EPG data stored by EPG services is for a particular time period dictated by the supplier of the EPG data. EPG services allows this time period to be adjustable by a user or an application. For example, a device application developer or a user may choose a time period of 2 days to conserve memory on the destination device even if the EPG data source provides a 5 day block of EPG data. A device application developer or a user may also choose to alter the amount of data stored for titles, descriptions, and other program attributes. The settings selected by a developer or an end-user can be applied to a specific channel, to favorite channels, or to all channels. In other words, the EPG data stored by EPG services can be customized to a particular application or user. At a minimum, a user is provided with enhanced EPG data listings that can be tailored by the user by many factors including but not limited to content, time, and geography. 
   The ability to tailor the content of EPG data using these attributes significantly enhances how a user may make use of EPG. For example, an application developer or a user may decide to download detailed information for programs occurring in the next two days and to download less detailed information for programs occurring on days three through five. In this example, the EPG data is temporally scaled or customized by the application. In addition to being able to temporally scale or filter EPG data, EPG services allows EPG data to be scaled by several factors including, but not limited to, channel, richness, language, and time. 
   Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims. These and other objects and features of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In order that the manner in which the above-recited and other advantages and objects of the invention are obtained, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. Understanding that these drawing depict only typical embodiments of the invention and are not therefore to be considered to be limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which: 
       FIG. 1  is a block diagram illustrating the scalability and extensibility of EPG data which is downloaded by a destination device implementing one embodiment of the present invention; 
       FIG. 2  illustrates an exemplary system for implementing EPG services; and 
       FIG. 3  is a detailed block diagram illustrating the reception of EPG data from an EPG data source and the transmission of EPG data from EPG services to one or more applications. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Electronic program guides (EPGs) are used to convey data to a user. Primarily, the data typically transmitted by an EPG data source is related to television programming and may include the titles of the television programs, the descriptions of the television programs, and other attributes and properties of the television programs. The EPGs are usually developed by EPG data providers that are responsible for the content of the EPG data. For instance, EPG data provided by an EPG data provider may be devoted exclusively to movie channels or EPG data can be devoted to public or free television channels. Currently, a recipient of EPG data is restricted to the format and content of a single EPG data provider. 
   EPGs, however, can also be used to convey other types of information such as radio schedules, Internet streaming media event schedules, information related to the Internet, or the content of the Internet. This document focuses on EPG data relating to television programming, but other data that may be included in EPGs is within the scope of the present invention. The television programming represented by EPG data is frequently displayed in table form. Each row of the table contains a type of information such as the title of the television programs, or a description of the television program, while each column is usually represents a time period or time block. As described previously, a destination device is currently unable to alter these characteristics and must accept the EPG data as it is formatted by an EPG data source. 
   EPG services overcomes the limitations of the prior art in at least two ways. Instead of simply receiving what an EPG data provider is transmitting, EPG services allows incoming EPG data to be extensibly scaled according to a several different factors or axes. For example, if the EPG data is temporally scaled, EPG services may receive detailed EPG data about television programs airing in the near future and coarse EPG data related to television programs airing further in the future. 
   In addition, EPG services permits a recipient of EPG data to determine the amount of descriptive EPG data such as titles, descriptions and attributes that is received. For television programs airing in the near future, the EPG data may be rich in content by including detailed descriptions while the EPG for television programs airing in the more distant future may include the titles and exclude the descriptions. 
   In addition to providing temporal and selective scalability, EPG services is capable or receiving EPG data from more than one EPG data source or provider. EPG services provides a loader module for each EPG data source and an abstraction layer or writer interface that interfaces with all of the loader modules. The writer interface or abstraction layer allows the EPG data received by the loader modules to be stored in the memory or storage of the destination device. Applications may then access the EPG data through another abstraction layer or control interface. The EPG data source or provider may change over time, but the application using EPG data provided by that source or provider is unaffected by those changes because the EPG data is accessed through EPG services rather than from the EPG data source or provider directly. Correspondingly, the application can be updated without regard to the EPG data provider, because the EPG data is stored via the writer interface. 
   The invention is described using block diagrams and flow charts. Using the block diagrams and flow charts in this manner to describe and represent the invention should not be construed as limiting the scope of the invention. Rather, the block diagrams and flow charts are intended to illustrate exemplary embodiments of the present invention. 
   The embodiments of the present invention may comprise a special purpose or general purpose computer comprising various computer hardware. Embodiments within the scope of the present invention also include computer-readable media having computer-executable instructions or data structures stored thereon. Such computer-readable media can be any available media which can be accessed by a general purpose or special purpose computer. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired executable instructions or data structures and which can be accessed by a general purpose or special purpose computer, such as one included in a set top box. Computer-readable media may also include remote data stores such as web servers and other remotedata stores. When information is transferred or provided over a network or other communications connection to a computer, the computer properly views the connection as a computer-readable medium. Thus, such a connection is also properly termed a computer-readable medium. Combinations of the above should also be included within the scope of computer-readable media. Computer-executable instructions comprise, for example, instructions and data which cause a general purpose computer, special purpose computer, or special purpose processing device to perform a certain function or group of functions. The computer-executable instructions and associated data structures represent an example of program code means for executing the steps of the invention disclosed herein. 
   Although not required, the invention can be described in the general context of computer-executable instructions, such as program modules, being executed by one or more processors included, for example, in a set top box. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types. Moreover, those skilled in the art will appreciate that the invention may be practiced with other computer system configurations, including general purpose computers, personal computers, hand-held devices, multi-processor systems, microprocessor-based or programmable consumer electronics, network PCs, minicomputers, mainframe computers, and the like. 
   As used herein “EPG data” refers to television programming information, radio programming information, Internet content, scheduling information, titles, descriptions, movie reviews, ratings information, MPEG Streams, and any other type of data that may be retrieved from a source by an electronic device. The embodiments of the present invention described herein refer to television programming information, but the embodiments of the present invention easily extend to other types of EPG data. As used herein “digital recording” refers to copies of recordings of the data represented by the EPG data and includes but is not limited to television programming, radio programming and the like. 
     FIGS. 1 and 2  illustrate generally some of the advantages provided by EPG services. The overall purpose of EPG services is to collect remote and transient EPG data and store it to provide applications with fast access, rich content, and querying capabilities for the collected EPG data. For devices having high speednetwork connectivity, the EPG data may also be collected and accessed remotely. EPG services achieves these objectives by: allowing the EPG data to be scaled according to many different factors or axes; providing extensibility such that new sources and types of EPG data may be accessed; providing components or modules to collect the EPG data from EPG data sources and providers; and providing components or modules to access the EPG data that has been retrieved and stored by EPG services. 
     FIG. 1  is a block diagram illustrating a portion of the scalability that EPG services provides for EPG data. The EPG data in  FIG. 1  comprises titles  106 , descriptions  104  and attributes  102 . Titles  106 , descriptions  104  and attributes  102  are each an example of EPG data and the combination of titles  106 , descriptions  104  and attributes  102  is also an example of EPG data. EPG data may be retrieved from more than one EPG data source or provider, but the EPG data that is stored by EPG services may differ from the EPG data that was received from the EPG data source. Thus the amount of EPG data retrieved from a particular EPG that is actually stored can vary from completely excluding the EPG data to completely including the EPG data of a particular source. The EPG data illustrated in  FIG. 1  is intended to be illustrative of EPG data in general and does not exclude additional information from being included in the EPG data made available by other EPG data sources and providers. 
   EPG data may be scaled, in this example, according to the factors or axes of time, richness, channels and language. In  FIG. 1 , time  108  is depicted as the horizontal axis of EPG table  100 . Typically, EPG data is stored for two to seven days, but time  108  can be adjusted in one minute intervals to any desired interval. In addition, time  108  can be divided into shorter time intervals. The richness of the EPG data refers to the amount of data that is stored for television program titles, descriptions and attributes and the like. The richness of to time  108 . Thus, various intervals of time  108  may have varying levels of richness. 
   The channels is another scalable factor. In a default condition, EPG data is stored for viewable channels and no EPG data is stored for hidden or test channels. A user, however, may choose to remove a particular channel from the EPG data. In one embodiment, a removed channel is treated differently from a test or hidden channel. EPG data is still stored for removed channels, but the EPG data is not necessarily displayed to a user or an application. Another aspect of the scalability of EPG services is related to favorite or preferred channels. A channel that is designated as preferred or favorite may have EPG data that is more rich than the EPG data stored for other channels. In addition, a user has the ability to exclude certain channels or other attributes from being included in the EPG data. 
   The EPG data is also scalable with regard to language. This setting only applies, however, to the storage of textual data that describes a television program. The language used in the programming itself does not affect the scalability of the EPG data. The language setting only permits EPG data to be stored if the language matches the system language preferences. The described scalability factors of time, richness, channels and language are exemplary factors and do not limit the factors with which EPG data may be scaled. 
   EPG data table  100  in  FIG. 1  further illustrates an example of EPG data that has been scaled according to richness and time. The amount of data  109  is, in this illustration, indicative of the richness of the EPG data. Column  110  contains attributes  102 , descriptions  104  and titles  106 . The time period for column  110  is, in this example, the next two days of EPG data. The EPG data in column  110  is rich in that descriptions  104  are extremely detailed, titles  106  are complete, and many attributes  102  are detailed. Exemplary attributes include closed captioning, rating, stereo and more. 
   Column  111  is indicative, in this example, of a time period from day 3 to day 5. As illustrated, the amount of data  109  is less and is coarser or less rich than the EPG data stored in column  110 . Descriptions  104  in column  111  are not as detailed, but titles  106  are still complete and column  111  contains no attributes  102 . Similarly, column  112  is indicative of a time period from day 6 to day 7. Only titles  106  are stored in column  112 . Thus the EPG data stored in column  112  is less rich than the EPG data in column  111 . EPG data table  100  therefore illustrates EPG data that has been scaled with respect to time and richness or content. 
   The following table is another illustration of EPG data that has been scaled according to time, richness, and channel. The EPG data displayed to a user will reflect the EPG data indicated in the following table. 
   
     
       
         
             
             
             
             
           
             
                 
                 
             
             
                 
               Channel Type 
               EPG Data 
               Time 
             
             
                 
                 
             
           
          
             
                 
               Channels Hidden by 
               Title 
               Do not store 
             
             
                 
               EPG Data Provider 
               Description 
               Do not store 
             
             
                 
                 
               Attributes 
               Do not store 
             
             
                 
               Normal Channels 
               Title 
               Store 4 days 
             
             
                 
                 
               Description 
               Store 3 days 
             
             
                 
                 
               Attributes 
               Store 2 days 
             
             
                 
               Favorite Channels 
               Title 
               Store 5 days 
             
             
                 
                 
               Description 
               Store 5 days 
             
             
                 
                 
               Attributes 
               Store 5 days 
             
             
                 
                 
             
          
         
       
     
   
   The above table illustrates a scenario where no EPG data is stored for hidden channels, the richness of the EPG data stored for normal channels is greater for television programs airing in the near future, and the EPG data stored for favorite channels is very rich for the entire time period stored. In this manner, the EPG data can be scaled and stored in a variety of different combinations using a variety of factors. EPG services allows EPG data to be custom tailored for a particular application or user. Channels or other attributes or descriptions that are not of interest to a particular application or user may be excluded. 
     FIG. 2  is a block diagram illustrating an exemplary system capable of implementing one embodiment of the present invention.  FIG. 2  illustrates a device  20 , which may be a set top box, a computer, a video cassette recorder, a television tuner, a modem, a digital satellite tuner, or any other device capable of receiving EPG data. Device  20  receives EPG data from EPG data provider  70 . Exemplary EPG data providers or sources include television stations, Internet Service Providers (ISPs), and satellites. The EPG data may be transferred via in-band television signals, out-of-band television signals, Hyper Text Transfer Protocol (HTTP), File Transfer Protocol (FTP), Transmission Control Protocol/Internet Protocol (TCP/IP) sockets, or any other communication protocol. 
   Device  20  typically has at least one application  22  which is capable of utilizing the EPG data provided by EPG data provider  70 . EPG services  40  acts as an intermediary between EPG data provider  70  and application  22 . In this manner, both application  22  and EPG data provider  70  may change independent of the other without creating an incompatibility that may render application  22  incapable of receiving EPG data because EPG data provider  70  and application  22  interact with EPG services  40  rather than with each other. 
   One embodiment of EPG services  40  provides pluggable modules for EGP loaders  60 , EPG writer  43 , storage  42 , and EPG control  41 . EPG loaders  60  provide the ability to receive EPG data from EPG data providers. As new EPG data providers become available to device  20 , a new EPG loader  60  is added to EPG services  40 . The EPG loader added to the system for the new EPG data provider is capable of collecting the EPG data from the new EPG data provider. For example, an EPG loader  60  may be added to EPG services  40  which is capable of retrieving or collecting movie review data from an HTTP address. In addition, EGP loaders  60  can be added and removed from EPG services  40  as needed. When an EPG data provider  70  is no longer available, for example, the EPG loader corresponding to that EPG provider is removed from EPG services  40 . 
   EPG writer  43  is a component or module that stores the EPG data collected by EPG loaders  60  in storage  42  which is a database containing EPG data in one embodiment. Storage  42  is also an example of a computer-readable medium. EPG writer  43  is responsible, in this example, for enforcing the scaling of the EPG data as well as the maximum amount of storage  42  that may be used for storing EPG data. Thus, if an EPG loader attempts to store EPG data that is greater in size than the maximum amount of EPG data allowed, then EPG data relating to television programming furthest in the future is removed until the EPG data being stored does not exceed the maximum storage amount allowed. 
   EPG writer  43  also removes EPG data from storage  42  that is no longer needed or usable. For instance, EPG writer  43  deletes the EPG data from storage  42  for all television programs which have aired before the current half-hour block. For example, at 8:15 a.m., EPG writer  43  will delete all EPG data relating to television programming occurring prior to 8:00 a.m. At 8:35 a.m., EPG writer  43  deletes television programming prior to 8:30 a.m. One reason for deleting EPG data and for limiting the amount of EPG data that can be downloaded is because storage  42  of device  20  is typically limited. 
   Because EPG services  40  may have a plurality of EPG loaders  60 , it is possible that one or more EPG loaders  60  will attempt to add EPG data to the same record or storage locations. More simply, it is possible for a conflict to arise with respect to the EPG data in a variety of contexts. For this reason, EPG services provides various schemes for resolving conflicts. For example, multiple loaders may attempt to update the description for the same program. To resolve this conflict, the EPG writer may be implemented to treat each EPG loader with a different priority. The EPG writer may permit higher priority loaders to take precedence. Another alternative for EPG loaders with equal priorities is to permit the last EPG data written to take precedence and be stored in storage  42 . Another alternative is to allow a user or application to select a conflict resolution scheme if conflicting EPG data sources are present. Simply stated, the user could designate a particular EPG data source or provider as having priority over another IPG data source or provider. These are examples of conflict resolution, but other methods orschemes may be employed. 
   It is also possible for EPG loaders  60  to implement a priority scheme independent of the EPG writer. This implementation, however, reduces the independent of the EPG loaders and forces more rigid interface and implementation constraints upon the development and design of the EPG loaders. In addition, EPG loaders  60  may be time based threads that activate and deactivate at predetermined times. 
   The retrieval of EPG data from storage  42  is performed by a control module illustrated as EPG control  41 , which is an example of a controller API in some embodiments. EPG control  41  may access: EPG data related to the available channels including channel number, channel station, network identification, station broadcast times and associated Uniform Resource Locators (URLs); EPG data related to information related to programming information including title, description, length, rating and other air times; or EPG data relating to whether the television program is purchasable, such as a pay-per-view movie or event. The EPG data can be accessed and retrieved by EPG control  41  in a variety of different combinations. 
   The ability to access and retrieve EPG data is enhanced by the querying capabilities supplied by EPG control. EPG data can be searched by many parameters, including but not limited to, time, title, description, category or other attribute which may be user defined. In this manner, the EPG data retrieved by an application can be extremely customized for an application. For high performance applications, EPG control  41  is also capable of notifying application  22  when the EPG data within a particular range changes. This enables applications  22  to maintain up to date EPG data available. 
     FIG. 3  is a detailed block diagram of a system implementing one embodiment of the present invention. Device  20  has one or more applications  22  which are capable of using EPG data. The EPG data retrieved by applications  22  may be displayed to a user via a television screen or a computer screen, or may be sent to a printer or other rendering device. EPG data is typically generated by EPG data providers  70 , which are shown in  FIG. 3  as listings provider  74 , movie descriptions provider  75  and satellite listings provider  76 . In this example, the EPG data generated by listings provider  74  is transmitted via a television station  71 , the EPG data generated by movie descriptions provider  75  is transmitted via an Internet Service Provider (ISP)  72 , and the EPG data generated by satellite listings provider  76  is transmitted via satellite  73 . It is understood that EPG data can be transmitted in a variety of different methods and that the transmission of EPG data described herein is exemplary rather than limiting. For instance, listings provider  74  may also transmit via ISP  72 . 
   The EPG data provided by EPG data providers  70  is received at device  20  by EPG services  40  which comprises EPG loaders  60 . An EPG loader or loader module has the responsibility of collecting EPG data from its native transmission format. EPG loaders  60  comprises one or more specific EPG loaders because as illustrated by the various EPG data providers  70 , EPG data can be transmitted in a variety of different methods and formats and new sources or providers of EPG data may become available in the future. For these and other reasons, each loader module collects EPG data, in this embodiment, from a particular source or provider. 
     FIG. 3  illustrates a Vertical Blanking Interval (VBI) loader module  61 , a HTTP loader module  62  and a MPEG loader module  63 . VBI loader module  61  is capable of collecting EPG data from the VBI of a television signal or broadcast. HTTP loader module  62  is capable of collecting EPG data over a network such as the Internet, and MPEG loader module  63  is capable of collecting or retrieving EPG data from a digital stream provided by satellite  73 . EPG loaders  60  allow EPG data to be collected from any communication system or protocol and are not limited to those illustrated in  FIG. 3 . 
   In addition to understanding the transmission medium and format of a particular EPG data provider  70 , Each EPG loader module optionally comprises the hardware and software necessary to accomplish this task. This is illustrated by HTTP loader module  62  which comprises a protocol  64 , a device driver  65  and a modem  66 . For HTTP loader module  62 , protocol  64  may be HTTP and TCP/IP if the transmission medium is the Internet. Typically, modem  66  is the hardware required to access the Internet, but access can be accomplished with other hardware components such as a network interface cards. Device driver  65  is typically a software module designed for a particular hardware component such as modem  66 . 
   Conflict resolution  44  is an optional pluggable component that permits a user to specify the actions to be taken when one or more EPG data providers  70  conflict. The action taken by conflict resolution  44  can be specified by the user, the application  22  or the supplier of the EPG data. For instance, the user could specify that conflict resolution  44  cause movie descriptions provider  75  to have priority over satellite listing sprovider  76 . In this instance, the portions of the EPG data provided by satellite listings provider  76  that conflict with the EPG data provided by movie descriptions provider  75  are discarded or otherwise handled. Conflict resolution  44  is extensible and can be implemented by attribute as well as by EPG data provider. Conflict resolution  44  can also be implemented at the EPG loader level, whereby the EPG loaders resolve conflicts. 
   Each EPG loader  60  is capable of interacting with EPG writer  43 . EPG writer  43  comprises an applications programming interface (API), in one embodiment, which is used by EPG loaders  60  to interface with EPG writer  43 . The collected EPG data is placed in storage  42  by EPG writer  43 . Typically, EPG loader  60  creates an instance of EPG writer  43  to perform updates to storage  42 , which may be a local or remote data store. EPG writer  43  provides methods having one or more parameters that allow the EPG data collected by EPG loaders  60  to be placed in storage  42  such that the EPG data may be queried and retrieved by EPG control  41 . 
   EPG writer  43  provides the following properties, methods or functions. AudioSubChannel adds a new audio subchannel format and has the parameters languageCode, isMainAudioService, isDolbyEncoded, and programType. AudioSubChannelForScheduleEntry adds a new audio subchannel to a schedule entry and has the parameters scheduleDataID and audioDataID. CategorizationSystem adds a new categorization system to the data store and has the parameters categorizationSystemName and pSystemDataID. CategoryPair adds a new category or subcategory pair to the data store. 
   CategoryForProgram maps a category pair to a specific program and has the parameters programDataID and categoryPairDataID. Channel adds a new channel to the data store and has the parameters serviceRecordID, channel, network, station, description, channelTtype, startSeconds, and pChannelDataID. ClearAll removes all data from the data store and has no parameters. ClearChannels removes all channel data from the data store and has no parameters. ClearPrograms removes all program data from the data store and has no parameters. ClearScheduleEntries removes all schedule data from the data store. DeleteAudioSubChannel removes a specific audio subchannel from the data store and has the parameter audioDataID. 
   DeleteCategorizationSystem removes a specific categorization system from the data store and has the parameter systemDataID. DeleteCategoryPair removes a specific category pair from the data store and has the parameters systemDataID, categoryName, and subCategoryName. DeleteChannel removes a specific channel from the data store had has the parameter ChannelObject. DeleteProgram removes a specific program from the data store and has the parameter ProgramObject. DeletePropertyForChannel removes a property from a channel object and has the parameters pChannelObject and propertyName. DeletePropertyForProgram removes a property from a program object and has the parameters pProgramObject and propertyName. 
   DeletePropertyForScheduleEntry removes a property from a schedule entry and has the parameters pScheduleEntryObject and propertyName. DeletePropertyForWeblink removes a property from a weblink object and has the parameters pWeblinkObject and propertyName. DeleteScheduleEntry removes a specific schedule entry from the data store and has the parameter ScheduleEntryObject. DeleteSharingDay removes a specific sharing day from the data store and has the parameter sharingDayDataID. DeleteVideoSubChannel removes a specific video subchannel from the data store and has the parameter videoDataID. DeleteWeblink removes a specific Web link from the data store and has the parameter WeblinkObject. 
   EnableDuplicateChecking sets the preferred result for this condition and has the parameter preventDuplicates. Program adds a new program to the data store and has the parameters programTitle, programDescription, yearMade, seconds, and programDataID. PropertyForChannel adds an extensible name-value property to a specific channel and has the parameters channelDataID, name and value. PropertyForProgram adds an extensible name-value property to a specific program and has the parameters programDataID, name, and value. PropertyForScheduleEntry adds an extensible name-value property to a specific schedule entry and has the parameters scheduleEntryDataID, name, and value. PropertyForWeblink adds an extensible name-value property to a specific Weblink and has the parameters weblinkDataID, name, and value. 
   PurchaseStringForScheduleEntry adds a new purchase string to a specific schedule entry and has the parameters scheduleEntryDataID and purchaseString, which is frequently encrypted. RatingForProgram maps a rating authority and rating to a specific program and has the parameters program DataID, and ratingCode. RemoveOldScheduleEntriesAndPrograms removes schedule entries before a specific time and their associated program, rating, category, property, and Web link data and has the parameter beforeThisTime. ScheduleEntry adds a new schedule entry to the data store and has the parameters eventID, channelDataID, startTime, endTime, cc, rerun, videoDataID, audioDataID, and scheduleEntryDataID. SharingDay adds a unique sharing day to the data store and has the parameters startDay, startTime, endDay, endTime, and pSharingDataID. SharingDayForChannel links a unique sharing day to a particular channel and has the parameters channelDataID, and sharingDataID. 
   UpdateComplete indicates the current set of updates to the data store is complete. VideoSubChannel indicates the current set of updates to the EPG services storage or data store is completer and has the parameters language, aspectRation, videoSourceHeight, videoSourceWidth, squarePixel, componentType, streamed, and pVideoDataID. VideoSubChannelForScheduleEntry creates a relationship between a schedule entry and a video subchannel and ahs the parameters scheduleEntryDatalD and videoDataID. 
   Weblink adds a new Web link to the data store and has the parameters url, description, startTime, endTime and pWeblinkDataID. WeblinkForChannel maps a Weblink to a specific channel and has the parameters channelDataID, and weblinkDataID. WeblinkForProgram maps a Web link to a specific program and has the parameters programDataID, and weblinkDataID. WeblinkForScheduleEntry maps a Web link to a specific schedule entry and has the parameters scheduleEntryDatalD and weblinkDataID. 
   While EPG loaders  60  place EPG data in storage  42  via EPG writer  43 , EPG control  41  performs the functions necessary to retrieve the EPG data from storage  42 . EPG control  41 , in one embodiment also comprises an API that provides functions and methods to application  22  that assist in the access and retrieval of EPG data. For example, it is necessary in many instances for EPG control  41  to determine if the necessary EPG data is available in storage  42 . Functions and methods are also provided by EPG control  41  that are able to access and retrieve EPG data relates to channels. 
   While a program is typically a unique event, programs may be repeated by a television station and may therefore correspond to one or more schedule entries. To retrieve EPG data concerning a program, EPG control  41  provides methods and functions for use with schedule entries. Programs may also belong to one or more categories or subcategories and EPG control  41  provides functions to retrieve the valid category and subcategory pairs. 
   Programs also may have one or more ratings which correspond to different rating authorities and EPG control  41  has functions and methods to access ratings. Some applications  22  may request notification of changes to the EPG data that may occur within a particular time range. EPG control  41  services these requests and fires an event when the EPG data changes. Typically, only one event may be requested for each instance of EPG control  41 . EPG control  41  provides properties, methods, and events, generally designated as functions, which allow EPG control  41  to be used by an application to access storage  42  or other data store. 
   The properties of EPG control  41  are as follows. CategorizationSystems retrieves a collection of the names of known schemes for organizing programs by type and has the parameter psystems. DataEndTime returns the time in the future at which the available data ends and has the parameter pEndTime. HighestDataStartTime returns the furthest time in the future when a program starts and has the parameter pStartTime. IsAnyDataAvailable returns information to confirm if valid channel or guide listings exist in the data store and has the parameter pDataAvailable. IsChannelDataAvailable returns information to indicate if channel data exists in the data store and has the parameter pChannelDataAvailable. RatingSystem retrieves a collection of strings for the names of known schemes or systems for organizing content ratings and has the parameter psystems. AvailableChannels retrieves the Channels collection object and has the parameter pChannels. 
   The methods of EPG control  41  are as follows. CancelCategoryEventRequest disables signaling of OnCategoryUpdate events. CancelChannelEventRequest disables signaling of OnChannelUpdate events. CancelRangeEventRequest disables signaling of OnRangeUpdate events. Categories retrieves a collection of the names of main categories within a categorization system for a given categorization system name and has the parameters categorizationSystemName and pCategories. ChannelsForProviderNetworkName returns channels matching the search value and has the parameters searchString, substringMatch, and pChannels. ChannelsForNumber retrieves a Channels collection object for valid device channels with a particular channel number or tuple and has the parameters serviceSpace, channel, time, and pChannels. ChannelsForProviderName returns channels matching the search value and has the parameters searchString, substringMatch, and pChannels. 
   IsScheduleDataAvailable returns information indicating whether EPG data is found for a range and has the parameters startTime, endTime, and pScheduleDataAvailable. Program retrieves the Program object representing the program shown on the specified channel at the specified time and has the parameters serviceSpace, channel, time and pProgram. ProgramEndTime retrieves the end time for the program shown on the specified channel at the specified time and has the parameters serviceSpace, channel, time and pEndTime. 
   ProgramLength retrieves the length in seconds for the program shown and the specified channel and the specified time and has the parameters serviceSpace, channel, time, and pSeconds. ProgramRating retrieves a Rating object for a particular program and has the parameters serviceSpace, channel, time, ratingSystem, and prating. ProgramStartTime retrieves the start time for a particular program shown on the specified channel at the specified time and has the parameters serviceSpace, channel, time, and pStartTime. ProgramTitle retrieves the name of the program shown on the specified channel at the specified time and has the parameters serviceSpace, channel, time, and pTitle. 
   RequestCategoryUpdateEvent indicates that an event should be fired when any aspect of the known categorization systems changes. RequestChannelUpdateEvent indicates that an event should be fired when a new channel has been added to the specified service space. RequestRangeUpdateEvent returns the update of the time range and has the parameters startTime and endTime. ScheduleEntries returns all schedule time slots matching the query values and has the parameters serviceSpace, channel, startTime, endTime, and pScheduleEntries. ScheduleEntriesForCategories returns programs that match the query values and has the parameters categorizationSystem, categories, startTime, endTime, maxhits, and pScheduleEntries. 
   ScheduleEntriesForProgramProperty returns programs matching the query values and has the parameters name, value, startTime, endTime, maxHits, and pScheduleEntries. ScheduleEntriesForProperty returns time slots matching query values and has the parameters name, value, startTime, endTime, maxHits, and pScheduleEntries. ScheduleEntriesForStrings retrieves a ScheduleEntries collection object representing all time periods for programs whose title or description includes a particular case-insensitive string which will be shown and has the parameters searchStrings, subStringMatch, findTitle, findDescription, startTime, endTime, maxHits, and pScheduleEntries. ScheduleEntry returns a time slot matching query values, and has the parameters serviceSpace, channel, time, and pScheduleEntry. SubCategories retrieves a collection of the names of subcategories within a categorization system for a given categorization system name and category name and has the parameters categorizationSystemName, categoryIndex, and pSubCategories. 
   The EPG control  41  events are as follows. OnCategoryUpdate indicates that a new category has been added. OnChannelUpdate indicates that a new channel has been added. OnRangeUpdate indicates that the data within the time range specified by RequestRangeUpdateEvent has changed. 
   The extensible properties of a channel, program, schedule entry, weblink or other EPG data is retrieved in one embodiment through the use of EPG control objects which include CategoryPair, CategoryPairs, Channel, Channels, GuideRating, GuideRatings, Program, Programs, PurchaseStrings, ScheduleEntry, ScheduleEntries, Weblink, Weblinks, SharingSchedule, MajorMinorSelectorIDs, and Tuple. These objects and associated methods are detailed in the previously incorporated provisional application. While the APIs of the invention have been described herein with reference to specific functions and parameters, the invention also extends to other APIs that provide similar functionality. 
   EPG services is intended to provide extensibility to EPG data. As illustrated, new sources of EPG data are easily accommodated by a device. The EPG data can be scaled and formatted in a variety of ways. Extensible properties can be added to the channel, program schedule entry, or weblink data and multiple properties may be added to the same set of EPG data, which enhances the ability of applications to search and utilize the stored EPG data. 
   EPG Data Map is another component of EPG services that is used to retrieve necessary data from EPG services, but should not be used by EPG loaders or other applications or components. EPG Data Map, in one embodiment, is an API. 
   EPG Data Map provides the following methods and functions. NetworkCallLetters retrieves the network name for a specific service record ID and has the parameters serviceRecordID, time, and pNetworkCallLetters. ProgramEndTime retrieves the end time for the program shown on the specified channel at the specified time and has the parameters serviceRecordID, time, and pEndTime. ProgramLength retrieves the length in seconds for the program shown on the specified channel at the specified time and has the parameters serviceRecordID, time, and pSeconds. ProgramPurchaseString retrieves the available purchase strings for a specified program and has the parameters serviceRecordID, time, cDims, pcDims, and pPurchaseStrings. ProgramRatings retrieves Ratings objects for the program shown on the specified channel at the specified time and has the parameters serviceRecordID, time, and pRatings. ProgramStartTime retrieves the start time for the program shown on the specified channel at the specified time and has the parameters serviceRecordID, time, and pStartTime. ProgramTitle retrieves the name of the program shown on the specified channel at the specified time and has the parameters serviceRecordID, time, and pTitle. ServiceRecordIDForNetworkCallLetters retrieves a ServiceRecordID that matches a specific network call letter string and has the parameters serviceSpace, searchstring, substringMatch, cDims, pcDims, and pServiceRecordIDs. ServiceRecordlDForStationCallLetters retrieves a ServiceRecordID that matches a specific station call letter string and has the parameters serviceSpace, searchString, substringMatch, cDims, pcDims, and pServiceRecordIDs. StationCallLetters retrieves the station name for a specific service record ID and has the parameters serviceRecordID, time, minorChannel, and pStationCallLetters. 
   The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.