ReferentialConstraint Element (Association SSDL)
The ReferentialConstraint element on an Association specifies direction in a relationship in the store schema definition language (SSDL) within the Entity Data Model (EDM). A ReferentialConstraint in SSDL is based on a foreign key constraint in the data source. Associations in the EDM are navigable in either direction; the roles of the Principal Role and Dependent Role elements of a ReferentialConstraint have corresponding foreign key relationships in the database.
The following schema specifies direction using the Principal Role and Dependent Role attributes of a ReferentialConstraint element. In the data table, the DependentRole has a foreign key containing the ManagerID.
<Association Name="FK_Employee_Employee_ManagerID">
<End Role="Employee" Type="Adventureworks.Store.Employee" Multiplicity="0..1" />
<End Role="Employee1" Type="Adventureworks.Store.Employee" Multiplicity="*" />
<ReferentialConstraint>
<Principal Role="Employee">
<PropertyRef Name="EmployeeID" />
</Principal>
<Dependent Role="Employee1">
<PropertyRef Name="ManagerID" />
</Dependent>
</ReferentialConstraint>
</Association>