Reference to existing attribute value

shumba · March 15th, 2006, 02:39 PM

I have an instance document in which I need to enforce that an attribute value is unique. Also, some other element of the document relates to this unique attribute value.

Here is an example XML instance document I made up to explain my problem

Code:

<?xml version="1.0" encoding="UTF-8"?>
<parts xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xsi:noNamespaceSchemaLocation="test.xsd">
   <part ref="44" name="processor">
      <description>Standard floppy</description>
      <related-part>4</related-part>
   </part>
   <part ref="4" name="motherboard">
      <description>Standard floppy</description>
      <related-part>55</related-part>
   </part>
</parts>

And here is the XML Schema document

Code:

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">

   <xs:element name="parts">
      <xs:complexType>
         <xs:sequence>
            <xs:element name="part" type="partType" minOccurs="2" maxOccurs="unbounded"/>
         </xs:sequence>
      </xs:complexType>
      <!-- Each part must have a unique "ref" attribute and "name" combination 
         Same part for different computer make could have the same name but needs
         a different reference to track the part -->
      <xs:unique name="partRef">
         <xs:selector xpath="part"/>
         <xs:field xpath="@ref"/>
      </xs:unique>
      <xs:unique name="partRefAndName">
         <xs:selector xpath="item"/>
         <xs:field xpath="@partNum"/>
         <xs:field xpath="productName"/>
      </xs:unique>
   </xs:element>

   <xs:complexType name="partType">
      <xs:sequence>
         <xs:element name="description" type="xs:string"/>
         <xs:element name="related-part" maxOccurs="unbounded"/>
      </xs:sequence>
      <!-- Update to use attribute group
         Remove whitespaces in names -->
      <xs:attribute name="name" type="xs:token" use="required"/>
      <xs:attribute name="ref" type="xs:positiveInteger" use="required"/>
   </xs:complexType>
</xs:schema>

Now within the parts context, I want to create a key to the @ref attribute and ensure that the value of related-parts refers to a existing @ref

I have done this below but it does not work - no error messages

Code:

      <xs:key name="key">
         <xs:selector xpath="part"/>
         <xs:field xpath="@ref"/>
      </xs:key>
      <xs:keyref name="refKey" refer="key">
         <xs:selector xpath="part"/>
         <xs:field xpath="related-parts"/>
      </xs:keyref>

Please, let me know if you need more information

Thanks

shumba · March 15th, 2006, 02:53 PM

ok. Got it but not sure if it is the best way to do it. Please advise at any rate. Thanks

Code:

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">

   <xs:element name="parts">
      <xs:complexType>
         <xs:sequence>
            <xs:element name="part" type="partType" minOccurs="2" maxOccurs="unbounded"/>
         </xs:sequence>
      </xs:complexType>
      <!-- Each part must have a unique "ref" attribute and "name" combination 
         Same part for different computer make could have the same name but needs
         a different reference to track the part -->
      <xs:unique name="partRef">
         <xs:selector xpath="part"/>
         <xs:field xpath="@ref"/>
      </xs:unique>
      <xs:unique name="partRefAndName">
         <xs:selector xpath="part"/>
         <xs:field xpath="@partNum"/>
         <xs:field xpath="productName"/>
      </xs:unique>


      <xs:key name="key">
         <xs:selector xpath="part"/>
         <xs:field xpath="@ref"/>
      </xs:key>
      <xs:keyref name="refKey" refer="key">
         <xs:selector xpath="part/related-part"/>
         <xs:field xpath="."/>
      </xs:keyref>

   </xs:element>

   <xs:complexType name="partType">
      <xs:sequence>
         <xs:element name="description" type="xs:string"/>
         <xs:element name="related-part" type="xs:positiveInteger" maxOccurs="unbounded"/>
      </xs:sequence>
      <!-- Update to use attribute group
         Remove whitespaces in names -->
      <xs:attribute name="name" type="xs:token" use="required"/>
      <xs:attribute name="ref" type="xs:positiveInteger" use="required"/>
   </xs:complexType>
</xs:schema>