An overview of the MPEG-7 description definition language (DDL)

This paper presents an overview of the MPEG-7 description definition language (DDL). The DDL provides the syntactic rules for creating, combining, extending and refining MPEG-7 descriptors (Ds) and description schemes (DSs). In the interests of interoperability, the W3C's XML Schema language, with the addition of certain MPEG-7-specific extensions, has been chosen as the DDL. This paper describes the background to this decision and using examples, provides an overview of the core XML Schema features used within MPEG-7 and the extensions made in order to satisfy the MPEG-7 DDL requirements.