ISO 21961:2003 gives requirements and defines the syntax of a specification language to be used in the creation of a data entity dictionary (DED).
A data entity is a concept that can, or does, take on one or more values. Semantics of a data entity, such as a text definition of its meaning, are defined by attributes. The purpose of ISO 21961:2003 is to define a language for specifying a dictionary which describes semantics for a collection of data entities; it does not define a specific dictionary. A dictionary is understood as a mechanism that is able to organize a set of information in a consistent and easily understandable manner, and it is commonly used by humans to look up the meaning of words used in natural languages. Similarly, a data entity dictionary (DED) is used by humans and systems to look up the definition, and other attributes, of data entities used in the definition and generation of data products.
ISO 21961:2003 defines the abstract definition of the semantic information that is required to be conveyed and presents the specification in a layered manner (attributes, entities, dictionaries). This is done so that the actual technique used to convey the information is independent of the information content and, therefore, the same abstract standard can be used within different formatting environments. This also permits the semantic information to be translated to different representations as may be needed when data are transferred across different domains.
ISO 21961:2003 defines the concepts of name, definition, units, and a small set of other standard attributes so that they may be used consistently in the formation of data entity dictionaries. Several classes of data entities are defined. These classes allow making a distinction between the abstract data entities, the models, and the concrete data entities, the data fields in a data product.