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XML Schema field Element

Definition and Usage

The field element specifies an XPath expression that identifies the value (or one of the values) used to define the identity constraint (unique, key, and keyref elements).

Element Information

-Parent elements: key, keyref, unique

Syntax

(? symbol declaration within the field element, which can appear zero or one time.)

Attribute Description
id Optional. Specifies a unique ID for the element.
xpath Required. Identifies a single element or attribute whose content or value is used for the constraint. If the expression identifies an element, it must be of simple type.
xml:lang Optional. Specifies the language used in the content.

Example 1

The following example shows a field element that defines the "userID" attribute as the field used for the identity constraint:

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