1 Introduction

The Store Schema Definition Language (SSDL) file format describes the store schema in the Entity Data Model (EDM). SSDL is a language based on XML that can be used for defining storage models by using the EDM. SSDL is used to describe storage metadata and schema using concepts from the entity-relationship model.

Entities are instances of entity types (such as Customer or Employee) that are richly structured records with a key. The structure of an entity type is provided by its properties. An entity key is formed from a subset of the properties of the entity type. The key (such as CustomerId or EmployeeId) is a fundamental concept to uniquely identify and persist entity instances and to enable entity instances to participate in relationships or associations.

Entities are grouped into entity sets; for example, the Customers entity set is a set of Customer instances.

Associations (sometimes referred to as relationships) are instances of association types. Association types are used to specify a named relationship between two entity types. Thus, an association is a named relationship between two or more entities. Associations are grouped into association sets.

Unlike conceptual schema definition language (CSDL), SSDL does not support the following concepts:

• Complex types

• Inheritance

• Navigation properties

• Function imports

SSDL does include the concept of functions that allow store functions and stored procedures to be defined and represented as part of the store metadata.

Entity sets and association sets are grouped into one or more entity containers. Entity containers are conceptually similar to databases; however, because entity types and association types are declared outside an entity container, they can be re-used across entity containers.

Additionally, although CSDL is independent of any particular database, an instance of SSDL is tied to a particular database. In order to specify SSDL, it is necessary to reference the EDM-enabled ADO.NET provider in addition to a provider manifest token. The provider manifest token identifies a provider manifest that is built into the provider and specifies which data types and database functions are supported by the provider. The provider manifest also specifies which primitive EDM type each store data type maps to. For more information about provider manifests, see [MSDN-PMS].

Sections 1.7 and 2 of this specification are normative. All other sections and examples in this specification are informative.