Graphical Representation

Summary

The <keyRef> element defines a reference to a key or unique constraint.

Creating

A <keyRef> can only be added to an element object. This can be done using the right click context menu on any of these entities.

Properties

Id - A user defined ID to uniquely identify the entity within the schema
Name - the name of the key.
Refer - the key or unique constraint to which this constraint refers.
XPath Fields - 1 or more XPath expressions that uniquely identify selected element.
XPath Selector - The XPath expression that identifies the element to which this key applies.

Sample

The following XSD code

<?xml version="1.0" encoding="utf-8" ?>


<!--Created with Liquid XML Studio (https://www.liquid-technologies.com)-->


<xs:schema attributeFormDefault="unqualified" elementFormDefault="qualified" xmlns:xs="http://www.w3.org/2001/XMLSchema">


  <xs:element name="library">


    <xs:complexType>


      <xs:sequence>


        <xs:element name="Book">


        ...


        </xs:element>


      </xs:sequence>


    </xs:complexType>


    <xs:key name="ID">


      <xs:selector xpath="Book|Author|Character" />


      <xs:field xpath="@id" />


    </xs:key>


    <xs:keyref name="IDREF" refer="ID">


      <xs:selector xpath="Book/Author-Ref|Book/Character-Ref" />


      <xs:field xpath="@ref" />


    </xs:keyref>


  </xs:element>


</xs:schema>





 

Will be represented like this