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Chapter 2 Building an XML model
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,
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 |
| (See Glossary) |
Code | Code of the unique constraint. It must be a |
Comment | Descriptive label of the unique constraint |
Stereotype | |
| 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.
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