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Defining identity constraints
70 PowerDesigner
To create an identity constraint from an element property sheet:
1 Click the Constraints tab of an element property sheet.
2 Click the Add Unique, Add Key or Add KeyRef Constraint tool in the
Constraints page.
An identity constraint appears in the list with predefined name and code
(a unique constraint in the example).
3 Modify the name and the code of the identity constraint.
4 Click OK.
Defining an identity constraint selector
An identity constraint selector specifies an XPath expression that selects a set
of elements for an identity constraint (unique, key or keyRef).
An XPath expression is limited to a subset of the full XPath language defined
in the W3C Recommendation XML Path Language 1.0.
An XPath expression allows you to locate a node (an element with its
ramifications) in the hierarchical tree structure of an XML document.