XML Schema unique Element


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Definition and Usage

The unique element defines that an element or an attribute value must be unique within the scope.

The unique element MUST contain the following (in order):

  • one and only one selector element  (contains an XPath expression that specifies the set of elements across which the values specified by field must be unique)
  • one or more field elements (contains an XPath expression that specifies the values that must be unique for the set of elements specified by the selector element)

Element Information

  • Parent elements: element

Syntax

<unique
id=ID
name=NCName
any attributes
>

(annotation?,(selector,field+))

</unique>

(The ? sign declares that the element can occur zero or one time inside the unique element)

Attribute Description
id Optional. Specifies a unique ID for the element
name Required. Specifies a name for the element
any attributes Optional. Specifies any other attributes with non-schema namespace

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