The DDL is used by MPEG-7 groups when they have to define any structured data model. For instance the MDS, audio and video groups are using it to define their descriptors and description schemes. The Call for Proposals was issued in October 1998.
Descriptors bind a feature to a set of values.
Description Schemes are models of the multimedia objects and of the universes that they represent e.g. the data model of the description. The DDL forms a core part of the MPEG-7 standard. It provides the solid descriptive foundation by which users can create their own Description Schemes and Descriptors. The DDL defines the syntactic rules to express and combine Description Schemes and Descriptors. The DDL must satisfy the MPEG-7 DDL requirements.