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Entity data model (EDM) refers to a set of concepts that describe data structure, regardless of its stored form. This model uses three key concepts to describe data structure: entity type, association type and property. EDM supports a set of primitive data types that define properties in a conceptual model.
The fundamental building block used to describe the structure of data within the entity data model (EDM) is the entity type. Entity type serves as a template for entities, which represent a specific object with a unique entity key within the entity set, a collection of instances of a specific entity type. In the conceptual model, entity types are constructed from properties and describe the structure of top-level concepts. Entity sets are grouped logically in an entity container.
The primitive data types supported by EDM include string, Boolean and Int32, among others. They are proxies for actual primitive data types supported in a storage or hosting environment. However, this model does not define the semantics of operations or conversion over primitive data types. Semantics are defined by the storage or hosting environment. EDM also supports inheritance for entity types where one entity type is derived from another.
EDM has namespaces, which work as abstract containers for entity types, complex types and associations. These namespaces provide context for the objects they contain and provide ways to disambiguate objects with the same name. EDM also provides XML syntax, which is called conceptual schema definition language.