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| <title>Referential integrity</title> |
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| |
| <h1 class="topictitle1">Referential integrity in the XML schema editor</h1> |
| <div><p>The XML schema editor has a built-in mechanism to handle referential |
| integrity issues. When you delete certain nodes, clean up for any nodes affected |
| will automatically occur.</p> |
| <div><p>When you define a complex type, you can add a content model to |
| it and reference a global element. </p><div class="skipspace"><div class="p">For example:<pre><schema> |
| <element name="comment" type="string"> |
| <complexType name="Items"> |
| <sequence> |
| <element ref="comment"> |
| </sequence> |
| </complexType> |
| </schema></pre> |
| </div> |
| <p>If the global element (comment) was deleted, |
| all references to it would be in error. However, when you delete the global |
| element, the XML schema editor will clean up using the following algorithm:</p> |
| <ul><li>If there are one or more global elements in the schema, it will change |
| all existing references to the first global element.</li> |
| <li>If there is no global element, then it will delete the element reference |
| from the content model.</li> |
| </ul> |
| <p>Similar cleanup operations are performed when other types of objects |
| are deleted. The following lists describes various cleanup operations. </p> |
| <p>Deleting |
| a global attribute will cause the following cleanup:</p> |
| <ul><li>Any item that references the deleted global attribute will be reset using |
| the preceding algorithm.</li> |
| </ol> |
| </ul> |
| <p>Deleting a complex type will cause the following cleanup:</p> |
| <ul> |
| <li>Any element type that is set to the deleted complex type will be reset |
| to the <tt class="sysout">string</tt> type.</li> |
| <li>Any complex type that derives from the deleted complex type will be reset |
| to no derivation.</li> |
| </ul> |
| <p>Deleting a simple type will cause the following cleanup:</p> |
| <ul> |
| <li>Any attribute type that is set to the deleted simple type will be reset |
| to the <tt class="sysout">string</tt> type.</li> |
| <li>Any element type that is set to the deleted simple type will be reset |
| to the <tt class="sysout">string</tt> type.</li> |
| <li>Any simple type that derives from the deleted simple type will be reset |
| to <tt class="sysout">string</tt> as its base type.</li> |
| </ul> |
| <p>Deleting a group or attribute group will cause the following cleanup:</p> |
| <ul> |
| <li>Any complex type that references the deleted group or attribute group |
| will be reset using the algorithm similar to the one described earlier for |
| deleted global elements.</li> |
| </ul> |
| </div> |
| <div class="section"><h4 class="sectiontitle">Deleting included and imported schema</h4><div class="p">If an included |
| or imported schema is deleted, you must manually reset the following type |
| references as appropriate: <ul><li>Global element and element's type</li> |
| <li>Attribute type</li> |
| <li>Complex type derivation</li> |
| <li>Simple type derivation</li> |
| </ul> |
| They will not automatically be reset if an included or imported schema |
| is deleted.</div> |
| </div> |
| </div> |
| <p><div class="relconcepts"><strong>Related concepts</strong><br /> |
| <div><a href="../topics/cxmlsced.html" title="XML schemas are an XML language for describing and constraining the content of XML files.">XML schema editor</a></div> |
| </p> |
| <p class="reltasks"><strong>Related tasks</strong><br /> |
| <div><a href="../topics/tedtschm.html" title="After you create an XML schema, you can edit its various properties, such as its namespace and prefix.">Editing XML schema properties</a></div> |
| </div> |
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