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Chapter 2 Building an XML model
XSM User's Guide 65
The UNIQUENUM unique constraint, defined on the project element,
specifies that the numEmployee attribute must be unique or null within the
employee element
To display a unique property sheet, double-click its name or its icon in the
Browser tree view.
Unique general properties
The General page of a unique property sheet displays the following
properties:
Property Description
Name Name of the unique constraint. It must be a no-colon-name
(See Glossary)
Code Code of the unique constraint. It must be a no-colon-name
Comment Descriptive label of the unique constraint
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 unique constraint. Its value must be of type ID and
unique within the model containing the unique constraint
Selector (XPath) An XML Path Language expression that selects a set of
elements across which the values specified in the Fields page
must be unique. There must be one and only one selector
For more information on Selector or XPath, see section Defining an
identity constraint selector.
Unique fields properties
The Fields page of a unique property sheet displays a list of XPath
expressions.
If there is more than one field (or XPath expression), the combination of
fields must be unique.
For more information on XPath expressions, see section Defining an
identity constraint selector.