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Defining identity constraints
72 PowerDesigner
Syntax Description
/book/chapter[2]/section[3] Selects the third section in the second chapter of
the book
employee[@dept=”doc”] Selects all the employee child elements of the
context node with a dept attribute set to doc
employee[@dept=”doc”][3] Selects the third employee child element of the
context node with a dept attribute set to doc
employee[3][@dept=”doc”] Selects the third employee child element of the
context node only if it has a dept attribute set to
doc
chapter[title] Selects the chapter child elements of the context
node with at least one title child element
chapter[title=”About this
book”]
Selects the chapter child elements of the context
node with at least one title child element with a
text content set to About this book
employee[@numEmployee and
@dept]
Selects all the employee child elements of the
context node with the numEmployee and dept
attributes
text() Selects all the child nodes of the text context
node
Defining selector general properties
The General page of a selector property sheet displays the following
properties:
Property Description
XPath An XPath expression relative to the parent element being
declared. It identifies the child elements to which the identity
constraint applies
Stereotype Sub-classification used to extend the semantics of an object
without changing its structure. It can be predefined or user-
defined
ID ID of the selector. Its value must be of type ID and unique within
the model containing the selector
To display a selector property sheet:
1 Type an XPath expression in the Selector groupbox of an identity
constraint (unique, key or keyRef) property sheet.