6.2.5 Keys

   The concept of a key, a set of attributes that defines uniqueness among the instances of a class, is already introduced in the Foundation Keys&Indexes package by the UniqueKey class. The Relational model extends the UniqueKey class to UniqueConstraint. Similarly, the Relational package uses KeyRelationship from the Foundation package as the basis of a ForeignKey. The generic associations of the Foundation’s UniqueKey and KeyRelationship between themselves, Class and StructuralFeatures are inherited by associations between UniqueConstraint, ForeignKey, Table, and Columns in the Relational package.

   UniqueKey

   KeyRelationship

   Attribute (fromCore)

   optionScopeColumnSet

   NamedColumnSet

   {ordered}

   ForeignKey/ownedElement

   /keyRelaitonship

   /namespace PrimaryKey

   /namespace /ownedElement

   /namespace

   Figure 6-9 UniqueConstraint and ForeignKey