Abstract:
A method and apparatus is provided for automatically classifying a multimedia artifact based on scoring, and selecting the appropriate set of ontologies from among all possible sets of ontologies, preferably using a recursive routing selection technique. The semantic tagging of the multimedia artifact is enhanced by applying only classifiers from the selected ontology, for use in classifying the multimedia artifact, wherein the classifiers are selected based on the context of the multimedia artifact. One embodiment of the invention, directed to a method for classifying a multimedia artifact, uses a specified criteria to select one or more ontologies, wherein the specified criteria indicates the comparative similarity between specified characteristics of the multimedia artifact and each ontology. The method further comprises scoring and selecting one or more classifiers from a plurality of classifiers that respectively correspond to semantic element of the selected ontologies, and evaluating the multimedia artifact using the selected classifiers to determine a classification for the multimedia artifact.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention disclosed and claimed herein generally pertains to selection of resources from among various methods of automatic content tagging in large scale systems. More particularly, the invention pertains to a method and apparatus for automatically classifying multimedia artifacts by scoring and selecting appropriate ontologies from amongst all possible sets of ontologies, such as by recursive routing selection. Even more particularly, the invention pertains to a method of the above type wherein the semantic tagging of the multimedia artifact is improved, or enhanced by applying only classifiers selected from the selected ontologies, based on the context of the multimedia artifact. 
         [0003]    2. Description of the Related Art 
         [0004]    Vast amounts of multimedia content are being created in many areas of science and commerce, necessitating the need for new automatic data analysis and knowledge discovery tools for more efficient data management. Semantic classification algorithms are being developed for classification to add metadata and facilitate semantic search. A principal challenge in semantic content modeling is the complexity of the modeled domain. Projecting multimedia content into a high-dimensional semantic space requires a suitable set of semantic classifiers that effectively and efficiently capture the underlying semantics of the data stream. Classifiers are often mapped to classes belonging to a specific ontology and specific domain, such as Broadcast News Video, Surveillance Video, Medical Imaging, Personal Photos, and the like. 
         [0005]    As processing power increases and data size increases exponentially, the number of classes that need to be detected, and can be detected, is also increasing considerably. Moreover, as the number and variety of automatic content classifiers increases, so does the entropy or randomness of the respective analysis system. Evaluating thousands of existing semantic concepts against terabytes of data is computationally expensive and redundant, and results in a computational bottleneck, or in an increased need for human experts who can select the appropriate set of classifiers to be automatically evaluated against a content item. Adding automatic classifiers results in a less efficient and less effective system, if the proper context of the automatic tagging is not included. At present, no solution exists for efficient traversing through the set of existing ontologies, and for the smart selection of classifiers associated with the respective ontologies in order to accommodate a large scale of classifiers and data. Moreover, automatic classifiers for the same class can differ significantly in the context of different ontologies;, for example, Person Activity in Surveillance Videos versus Person Activity in Broadcast News. The known solutions for selecting the most appropriate classifiers either adopt (or build) a single ontology, or else evaluate against a manually selected set of concepts within all available ontologies. This can compromise the quality of the content retrieval, since weak and redundant classifiers can have the same relevance in the semantic tagging as the more reliable ones. 
         [0006]    In recent years, a substantial amount of effort has been put into designing semantic concept detectors for various concepts of interest in different domains. The “Large Scale Concept Ontology for Multimedia”  IEEE Trans. Multimedia,  July 2006, initiative has identified nearly 1000 concepts of interest for visual analysis. For example, Kender and Naphade, in “Visual concepts for news story tracking: Analyzing and exploiting the NIST TRECVID video annotation experiment,”  IEEE Proc. Int. Conf. Computer Vision and Pattern Recognition  ( CVPR ), 2005, exploited the relationships between concepts, and used various criteria to determine the maturity of LSCOM concept definition and ontology completeness. Also, performance of semantic classifiers can be enhanced using context, as shown on a moderate-size lexicon by Naphade and Smith in “Mining the Semantics of Concepts and Context,”  Intl. Workshop on Multimedia Data Management  (MDM-KDD), 2003. However, ontologies offer varying interpretations of concepts when used within context. 
         [0007]    Moreover, analysis of vast amounts of image and video data available on internet blogs and web chat rooms has produced a need to analyze multiple modalities such as associated text, audio, speech, URL and XML data. This type of data is needed to automatically place a multimedia artifact in a context, and to offer clues that will result in correct ontology selection. For example, Benitez, Smith, and Chang introduced a multimedia knowledge representation framework of semantic and perceptual information in “MediaNet: A Multimedia Information Network for Knowledge Representation”,  Proc. SPIE  2000  Conference on Internet Multimedia Management Systems  (IS&amp;T/SPIE-2000), Vol. 4210, 2000. 
         [0008]    Reconciling ontology entries to create a normalized omniscient ontology may be virtually impossible. Thus, choosing the right set of ontologies, and the right set of classifiers for a multimedia artifact is one of the key problems in regard to large simultaneous information feeds of video streams that need to be analyzed and indexed. Statistical approaches to determine both classifiers and ontologies simultaneously need exhaustive evaluation and pruning in order to make an ontology manageable for a large number of classes. 
         [0009]    In the absence of a solution that addresses the above situation, selecting the right set of classifiers for multimedia artifacts that are based on the appropriate context and determined by the appropriate ontologies in a large scale classification system, will continue to be a problem. 
       SUMMARY OF THE INVENTION 
       [0010]    The invention generally pertains to a method and apparatus for automatically classifying a multimedia artifact based on scoring, and selecting the appropriate set of ontologies from among all possible sets of ontologies, preferably using a recursive routing selection technique. The semantic tagging of the multimedia artifact is enhanced by applying only classifiers from the selected ontology, for use in classifying the multimedia artifact, wherein the classifiers are selected based on the context of the multimedia artifact. One embodiment of the invention, directed to a method for classifying a multimedia artifact, uses a specified criteria to select one or more ontologies, wherein the specified criteria indicates the comparative similarity between specified characteristics of the multimedia artifact and specified characteristics of each ontology. The method further comprises scoring and selecting one or more classifiers from a plurality of classifiers that respectively correspond to semantic elements of the selected ontologies at the current granularity, and evaluating the multimedia artifact using the selected classifiers to determine a classification for the multimedia artifact. This is a recursive process, so scoring and selecting happens at every level of the hierarchy as traversing through the ontology continues. So, at every level, semantic characteristics differ (e.g. sports concept at one level, and scoring a goal at the next). One objective of the invention is to provide a method for selecting the most appropriate set of classifiers and/or ontology based on context, and to optimize the number of concepts that can be evaluated on a large collection without compromising the metadata enrichment or increasing the processing complexity. Further objectives are to select classification detectors on the basis of multimodal observations of the data, and to describe each classification method and ontology in terms of characteristics such as domain, quality and size. It is anticipated that embodiments of the invention will provide sub-optimal metadata enrichment of multimedia artifacts for arbitrary dataset size, computation and processing constraints. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself, however, as well as a preferred mode of use, further objectives and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein: 
           [0012]      FIG. 1  is a schematic drawing depicting an ontology and semantic-based metadata concept selection pipeline, for use in illustrating concepts of the invention. 
           [0013]      FIG. 2  is a block diagram showing a recursive router and other components for use in carrying out embodiments of the invention. 
           [0014]      FIG. 3  is a block diagram showing a data processing system that may be used to implement the recursive router of  FIG. 2 , and other components in embodiments of the invention. 
           [0015]      FIG. 4  is a schematic diagram showing one embodiment of the invention. 
           [0016]      FIG. 5  is a schematic diagram showing another embodiment of the invention in the different domain. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0017]    Referring to  FIG. 1 , there is shown a large scale classification system  100  for use in an embodiment of the invention. The system is configured to perform semantic tagging and classification of multimedia information that is provided by specified information sources.  FIG. 1  shows examples of such information sources, such as a Broadcast News source  102  that provides video information, Surveillance source  104  that provides video and raw archive images, and Blogs or other Internet sources  106  that provide personal images and photographs. 
         [0018]    As a first stage or step in the classification procedure described herein, it is necessary to select an ontology for the particular multimedia information, from all the ontologies that are available or pertinent to the particular information. This is shown by ontology selection stage  108  of  FIG. 1 . As is known by those of skill in the computer science and information science arts, an ontology is a data model that has an associated domain, and that is used to reason about objects in the domain and relations between objects. In addition to individual objects in its domain, an ontology has classes, which are sets, collections or different types of objects. An ontology also has associated attributes and semantic elements, where attributes are properties, features, characteristics or parameters that domain objects can have. Semantic elements of an ontology can be generic or specific entities, and can include, by way of example and not limitation, particular events, objects, activities, scenes, sites, people and/or organizations. 
         [0019]    In  FIG. 1 , a data object comprising information furnished by one of the sources  102 - 106 , wherein the object is in digital form and is to be classified and tagged by system  100 , is referred to hereinafter as a multimedia artifact. Examples of multimedia artifacts, as such term is used herein, include but are not limited to photographs, graphics, images, videos, audio, music, text, three dimensional objects, games, virtual worlds, XML, and/or other structured and unstructured information. A multimedia artifact is also characterized by semantic elements similar to the semantic elements associated with ontologies, as described above. In the system of  FIG. 1 , metadata pertaining to a given multimedia artifact can be used to select an ontology from the available ontologies that correspond to the given multimedia artifact. Examples of metadata, for a particular multimedia artifact, could include, without limitation, the artifact source, its image name, alt tag, attribute, the name of the collection to which the artifact belongs, and/or its general purpose. 
         [0020]    A further important characteristic of ontologies is that they may occur in a structure wherein there may be multiple ontologies that are horizontal, or on the same level. There may also be ontologies that are on different levels. For example,  FIG. 1  shows the ontology Multimedia  110 , which is on a level above ontologies  112 - 122 . Thus, if the Multimedia ontology  110  is selected in classifying a multimedia artifact, one or more of the ontologies  112 - 122  may also be selected to further refine artifact classification. 
         [0021]    Referring further to  FIG. 1 , after an ontology has been selected, semantic classifiers are also selected, at stage  124  of  FIG. 1 . In the classification procedure, semantic elements of a multimedia artifact are compared with semantic elements included in a selected ontology domain, in order to detect matches therebetween. A classifier is a mechanism that automatically routes this procedure down through the taxonomy, or classification structure of the ontology. Thus, if a match occurs with an ontology semantic element, and the element is a node that has a branch descending downwards or has leaves at a lower level, a classifier corresponding to the semantic element will direct the matching procedure down the branch to check for matches at lower levels. In carrying out this activity, the classifier may make use of algorithms, wherein the algorithms can use, without limitation, rule-based, statistical-based or hybrid classification methods. Such algorithms include, but are not limited to, neural networks, decision trees, Gaussian mixture models, hidden Markov models and support vector machines. These algorithms can use models developed to recognize, or identify semantic elements. 
         [0022]    As used herein, the term “evaluating a multimedia artifact”, means carrying out a comparison or classification procedure as described above. As the classifiers route the multimedia artifact through the classes of a selected ontology or ontologies, underlying semantics of the artifact are captured. That is, when matches occur between semantic elements of the multimedia artifact and those of the ontology classes, new metadata is discovered for the artifact. As a result, the multimedia artifact is automatically enriched with the most relevant metadata, which can pertain to both its context and its content. This enriching metadata can be used to tag the multimedia artifact, as shown by the automatic tagging stage  126  of  FIG. 1 . Enriched semantic metadata can be packaged with the multimedia artifact, or stored in an associated database. 
         [0023]    If there are multiple ontologies on the top level to be considered for a multimedia artifact, one or more of the ontologies is initially selected on the basis of some criteria. The selection can be based on context information, or other metadata for the multimedia artifact, if available. If metadata does not exist, the pertinence of each ontology is scored, based on artifact content, and the ontology or ontologies with the highest scores are selected. If there are multiple classifiers in the selected ontologies, the classifiers can also be scored to select those that are most pertinent to the multimedia artifact. The scoring activity can be carried out in connection with algorithms such as those referred to above. 
         [0024]    Referring to  FIG. 2 , there is shown a recursive router  202  configured with other components that can be operated collectively to carry out classification and tagging procedures for system  100 , as described above. Initially, a digital multimedia artifact  204  is inputted to router  202 , with or without metadata, and the artifact is recursively evaluated. If there is no metadata available, the multimedia artifact is classified only on the basis of its content, as likewise described above. Otherwise, the metadata is used in the classification. 
         [0025]    During successive recursions, the multimedia artifact is evaluated with respect to different ontologies from ontology database  206 . Router  202  derives a score for each ontology, based on the number of semantic elements from the ontology that are found to match, or be relevant to the, multimedia artifact. The scores of respective ontologies are ranked, and the ranking is used to select the ontology, or ontologies that are most appropriate to the multimedia artifact. Classifiers associated with the selected ontologies are then selected, from a classifier database  208 , based on the content and/or metadata of the multimedia artifact. The selected classifiers are used to evaluate the artifact, and scores are derived for the classifiers and ranked in like manner as the ontologies. The classification scores, together with existing metadata, are used to further refine traversal through the ontology structure for a set of classifiers to be evaluated during the subsequent cycle of recursive router  202 . Iterative refinement of automatic semantic tagging stops, when prespecified leaves are reached in the ontology database  206 . 
         [0026]    Using the recursive router arrangement of  FIG. 2 , evaluation of a multimedia artifact traverses a path that reaches classes at different levels of the ontology class hierarchy. Thus, there can be integration at different levels of decision, to enhance or enrich semantic metadata.  FIG. 2  further shows an output  210  comprising enriched metadata that is produced by the recursion process. The metadata can also be fed back to the recursive router, to further refine the next evaluation cycle. 
         [0027]    Referring to  FIG. 3 , there is shown a block diagram of a generalized data processing system  300  which may be adapted to provide recursive router  202  and other components shown in  FIG. 2 , as well as other components needed to implement embodiments of the invention described herein. It is to be emphasized, however, that the invention is by no means limited to such systems. For example, embodiments of the invention can also be implemented with a large distributed computer network and a service over the internet, as this can be applicable to distributed systems, LANs and WWWs. 
         [0028]    Data processing system  300  exemplifies a computer, in which code or instructions for implementing embodiments of the invention may be located. Data processing system  300  usefully employs a peripheral component interconnect (PCI) local bus architecture, although other bus architectures such as Accelerated Graphics Port (AGP) and Industry Standard Architecture (ISA) may alternatively be used.  FIG. 3  shows a processor  302  and main memory  304  connected to a PCI local bus  306  through a Host/PCI Cache bridge  308 . PCI bridge  308  also may include an integrated memory controller and cache memory for processor  302 . It is thus seen that data processing system  300  is provided with components that may readily be adapted to provide other components for implementing embodiments of the invention as described herein. Referring further to  FIG. 3 , there is shown a local area network (LAN) adapter  312 , a small computer system interface (SCSI) host bus adapter  310 , and an expansion bus interface  314  respectively connected to PCI local bus  306  by direct component connection. Audio adapter  316 , a graphics adapter  318 , and audio/video adapter  322  are connected to PCI local bus  306  by means of add-in boards inserted into expansion slots. SCSI host bus adapter  310  provides a connection for hard disk drive  320 , and also for CD-ROM drive  324 . 
         [0029]    Referring to  FIG. 4 , there is shown an embodiment of the invention wherein only one level of an ontology structure is traversed, in carrying out an algorithm to automatically select semantic classifiers for use in evaluating a multimedia artifact.  FIG. 4  shows a multimedia artifact comprising a photographic image  402  or the like, provided by Broadcast News source  102  as described above. Based on the source of artifact  402 , Broadcast News ontology  112  is selected from among the available multimedia ontologies  108 , that are shown in  FIG. 1 . 
         [0030]    Referring further to  FIG. 4 , there is shown a set  404  of general semantic classifiers at node level, under the Broadcast News ontology  112 , wherein set  404  comprises a superset of leaf classifiers. The genre for multimedia artifact  402  can be derived from such general semantic classifiers and from artifact context, such as the source and collection of multimedia artifact  402 , and its associated metadata.  FIG. 4  shows that by running the context, and/or content of multimedia artifact  402  against relevant genre classes, it can be determined that the political speech genre  406  is a genre for artifact  402 . This determination triggers specific semantic classifier leaf nodes in set  404 , including politics node  408  in the Program category, studio node  410  in the Location category, speech node  412  in the Activities and Events category and the maps node  414  in the Graphics category. Frequent concurrencies of high-level concepts can be used to trigger the most appropriate classifier nodes at each level of the ontology structure. More visual categories of the current analogy, such as the categories People  416  and Objects  418 , are triggered as a whole set. Iterative refinement of the People and Object categories  416  and  418 , at the level of the leaf classifiers of set  404 , is based on classification detection scores. Only the classifier concept nodes with the highest detection scores at this level are selected, such as the military leader node  420 , the face node  422 , and flag node  424 , as shown by  FIG. 4 . 
         [0031]    The effort to provide the information shown by  FIG. 4  describes one recursion in carrying out a classification procedure in accordance with the embodiment of the invention. There is only one recursion, since each of the classifier leaf nodes shown in  FIG. 4  is an ontology that might overlap with other ontologies. Therefore, the system carrying out the classification recursively selects the appropriate ontology based on classification of artifact and associated meta content, against the classes at each iteration level or recursion level. 
         [0032]    Referring to  FIG. 5 , there is shown an example of how an image can be automatically tagged with semantic labels from different ontologies, without exhaustive evaluation against thousands of classifiers. A multimedia artifact comprising an image  502  has a URL, HTML address, file name, date it was taken, and alt tag as input metadata  504 . The HTML address and alt tag select a Web Shopping ontology  506 . A file name, page source from the URL and alt tag select the Consumer Media and TV Fashion Shows ontology  508 , and Fashion Reviews in Broadcast News  510 . The image name entity, detected in the page URL, triggers the Name entity ontology and a related Designer profession  512 . 
         [0033]    After selecting pertinent ontologies, the next step is to determine the relevant branch in each selected ontology, based on the existing metadata  504 . Thus, Wedding branch  514  is selected from the Shopping Category  506 , based on the alt tag. At the next level below Fashion Shows  508 , scoring of the appropriate classifier is used to select Runway  516 . The date of the image  502  is then used to select Summer  518 , at the next following level. Classifier scoring is also used to select Long Dress  520 , and a combination of alt tag and scoring is used to select the Wedding category  522 . 
         [0034]    The arrangement of  FIG. 5 , the result at each level, is used both for metadata enrichments and for finer classifier selection. Also, ontologies can have overlapping branches. An example of this is Bridal Gowns  524  of Designer ontology  512  overlapping in part with Wedding Dresses  526  of Shopping ontology  506 . Moreover,  FIG. 5  illustrates how branches or tags from different ontologies can reach the same category, such as the Beaded category  528  and the Ivory category  530 . 
         [0035]    In embodiments of the invention, the ontology structure can be leveraged to avoid detecting the entire lexicon by smartly selecting concept detectors that need to be run on the data. In one approach, the frequent concurrencies of high-level concepts are used to devise a scheme for sub-optimal choice of the most appropriate concepts to evaluate against a multimedia artifact or collection item based on a tradeoff measure between another of the number of concepts evaluated, and metadata enrichment. The subset of classifiers is iteratively evaluated against a data sample, and weights assigned to the classifiers in a training phase are adapted based on sample content. 
         [0036]    The invention can take the form of an entirely software embodiment or an embodiment containing both hardware and software elements. In a preferred embodiment, the invention is implemented in software, which includes but is not limited to firmware, resident software, microcode, or the like. 
         [0037]    Furthermore, the invention can take the form of a computer program product accessible from a computer-usable or computer-readable medium providing program code for use by or in connection with a computer or any instruction execution system. For the purposes of this description, a computer-usable or computer readable medium can be any tangible apparatus that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus or device. 
         [0038]    The medium can be an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system (or apparatus or device), or a propagation medium. Current examples of optical disks include compact disk—read only memory (CD-ROM), compact disk—read/write (CD-R/W) and DVD. 
         [0039]    A data processing system suitable for storing and/or executing program code will include at least one processor coupled directly or indirectly to memory elements through a system bus. The memory elements can include local memory employed during actual execution of the program code, bulk storage, and cache memories which provide temporary storage of at least some program code in order to reduce the number of times code must be retrieved from bulk storage during execution. 
         [0040]    Input/output or I/O devices (including but not limited to keyboards, displays, pointing devices, etc.) can be coupled to the system either directly or through intervening I/O controllers. 
         [0041]    Network adapters may also be coupled to the system to enable the data processing system to become coupled to other data processing systems or remote printers or storage devices through intervening private or public networks. Modems, cable modem and Ethernet cards are just a few of the currently available types of network adapters. 
         [0042]    The description of the present invention has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiment was chosen and described in order to best explain the principles of the invention, the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated.