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TopMetadata are a representation of the administrative, descriptive, preservation, usage, and technical characteristics associated with multimedia objects; they can be extracted manually or automatically from multimedia documents. This value-added information helps bridge the semantic gap, described as: “The lack of coincidence between the information that one can extract from the visual data and the interpretation that the same data have for a user in a given situation” (Smeulders, Worring, Santini, Gupta, & Jain, 2000).
Because of the high cost and subjectivity associated with human-generated metadata, a large number of research initiatives are focusing on technologies that enable automatic classification and segmentation of digital resources. Many consortia are working on a number of projects to define multimedia metadata standards, in order to describe multimedia content in many different domains and to support sharing, exchanging, and interoperability across different platforms. They are distinguished in (Salvetti, Pieri, & Di Bono, 2004):
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Standardised description schemes that are directly related to the representation of multimedia content for a specific domain (like METS, MPEG-7);
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Standardised metadata frameworks that consider the possibility of integrating metadata standards mapped on different application domains, providing rich metadata models for media descriptions together with languages that allow one to define other description schemes for arbitrary domains (like PICS, RDF, MPEG-21).
For example, the vision of MPEG-21 is to define a multimedia framework that enables augmented and transparent use of multimedia resources across a wide range of networks and devices used by different communities. The intent is that this framework will cover the entire multimedia content delivery chain, including creation, production, delivery, personalization, presentation, and trade.
The development of metadata standards will increase the value of multimedia data, which are used by various applications. Nevertheless, there are disadvantages in current metadata representation schemes (Smith & Schirling, 2006), such as cost, unreliability, subjectivity, lack of authentication, and interoperability with respect to syntax, semantics, vocabularies, and languages (Salvetti, Pieri, & Di Bono, 2004).