xs:unique

Purpose

Defines an identity constraint of type xs:unique. The values of an identity constraint are extracted from an XML fragment that is validated against the parent element declaration. The values of an xs:unique identity constraint must be unique.

For details of the construction of the tuples representing the values of an identity constraint, please see section 3.11.4 Identity-constraint Definition Validation Rules of the W3C documentation XML Schema Part 1: Structures.

Parent element xs:element
Child elements xs:annotation, xs:field, xs:selector
Attributes id, name
Attributes
Name Type Description
id xs:ID Assigns an identifier to the schema node.
name xs:NCName

The names of all identity constraints (xs:key, xs:keyref and xs:unique) must be unique within a schema document.

An xs:unique identity constraint can be referenced by an xs:keyref identity constraint that cites the name of the xs:unique identity constraint in the refer attribute.