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xmlrecursionxsdxerceskeyref

XML, XSD xs:keyref within recursive complex type defintion

I have some xml data with a list of allowed types at the top and a recursive list type of objects and sub-objects that refer to the allowed types:

<?xml version="1.0" encoding="UTF-8"?>
<ROOT xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="KEYREF_TEST.xsd">
  <ALLOWED_SHAPE_TYPES>
    <SHAPE_TYPE>Circle</SHAPE_TYPE>
    <SHAPE_TYPE>Triangle</SHAPE_TYPE>
    <SHAPE_TYPE>Square</SHAPE_TYPE>
  </ALLOWED_SHAPE_TYPES>
  <SHAPES>
    <SHAPE>
      <TYPE>Triangle</TYPE>
      <SUB_SHAPES>
        <SHAPE>
          <TYPE>Circle</TYPE>
          <SUB_SHAPES/>
        </SHAPE>
        <SHAPE>
          <TYPE>Square</TYPE>
          <SUB_SHAPES>
            <SHAPE>
              <TYPE>Triangle</TYPE>
              <SUB_SHAPES/>
            </SHAPE>
          </SUB_SHAPES>
        </SHAPE>
      </SUB_SHAPES>
    </SHAPE>
    <SHAPE>
      <TYPE>Square</TYPE>
      <SUB_SHAPES/>
    </SHAPE>
  </SHAPES>
</ROOT>

I have defined the schema that validates this document as follows:

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
  <xs:element name="ROOT">
    <xs:complexType>
      <xs:sequence>
        <xs:element name="ALLOWED_SHAPE_TYPES">
          <xs:complexType>
            <xs:sequence minOccurs="0" maxOccurs="unbounded">
              <xs:element name="SHAPE_TYPE" type="xs:string"/>
            </xs:sequence>
          </xs:complexType>
        </xs:element>
        <xs:element name="SHAPES" type="shape-list-type"/>
      </xs:sequence>
    </xs:complexType>
    <xs:unique name="SHAPE_TYPE_UK">
      <xs:selector xpath="ALLOWED_SHAPE_TYPES/SHAPE_TYPE"/>
      <xs:field xpath="."/>
    </xs:unique>
  </xs:element>
  <xs:complexType name="shape-list-type">
    <xs:sequence>
      <xs:element name="SHAPE" minOccurs="0" maxOccurs="unbounded">
        <xs:complexType>
         <xs:sequence>
            <xs:element name="TYPE" type="xs:string">
              <xs:keyref name="SHAPE_TYPE_FK" refer="SHAPE_TYPE_UK">
                <xs:selector xpath="."></xs:selector>
                <xs:field xpath="."></xs:field>
              </xs:keyref>
            </xs:element>
            <xs:element name="SUB_SHAPES" type="shape-list-type"/>
          </xs:sequence>
        </xs:complexType>
      </xs:element>
    </xs:sequence>
  </xs:complexType>
</xs:schema>

When validating in oXygen 13.2 I get the following error:

System ID: C:\pvcswork\CodeSource\XMLSchema\KEYREF_DATA.xml
Main validation file: C:\pvcswork\CodeSource\XMLSchema\KEYREF_DATA.xml
Schema: C:\pvcswork\CodeSource\XMLSchema\KEYREF_TEST.xsd
Engine name: Xerces
Severity: error
Description: Identity Constraint error:  identity constraint "KeyRef@1df2ead" has a keyref which refers to a key or unique that is out of scope.
Start location: 10:28

I believe this is due to the xs:keyref being a child of the xs:complexType definition which is not a sub-element of the xs:element where the xs:unique is defined.

I could move the xs:keyref into the ROOT definition and target the TYPE elements with an XPath, but the // syntax is not permitted so I would lose the recursion and have to define a new xs:keyref for each level of nesting. ** UPDATE - // is permitted when at the start of the XPath, preceeded by a dot! **

Is there a solution I have missed (still using XSDs)? Thanks in advance..

Solution

  • The XSD below would be my solution to your problem. I basically fixed some of the selectors and put them at the same level.

    QTAssistant showing unique/keyref

    The XSD:

    <?xml version="1.0" encoding="UTF-8"?> 
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"> 
    <xs:element name="ROOT"> 
        <xs:complexType> 
            <xs:sequence> 
                <xs:element name="ALLOWED_SHAPE_TYPES"> 
                    <xs:complexType> 
                        <xs:sequence minOccurs="0" maxOccurs="unbounded"> 
                            <xs:element name="SHAPE_TYPE" type="xs:string"/> 
                        </xs:sequence> 
                    </xs:complexType> 
                </xs:element> 
                <xs:element name="SHAPES" type="shape-list-type"/> 
            </xs:sequence> 
        </xs:complexType> 
        <xs:unique name="SHAPE_TYPE_UK"> 
            <xs:selector xpath="ALLOWED_SHAPE_TYPES/SHAPE_TYPE"/> 
            <xs:field xpath="."/> 
        </xs:unique> 
        <xs:keyref name="SHAPE_TYPE_FK" refer="SHAPE_TYPE_UK"> 
            <xs:selector xpath=".//SHAPE/TYPE"></xs:selector> 
            <xs:field xpath="."></xs:field> 
        </xs:keyref>        
    </xs:element> 
    <xs:complexType name="shape-list-type"> 
        <xs:sequence> 
            <xs:element name="SHAPE" minOccurs="0" maxOccurs="unbounded"> 
                <xs:complexType> 
                    <xs:sequence> 
                        <xs:element name="TYPE" type="xs:string"/> 
                        <xs:element name="SUB_SHAPES" type="shape-list-type"/> 
                    </xs:sequence> 
                </xs:complexType> 
            </xs:element> 
        </xs:sequence> 
    </xs:complexType> 
</xs:schema>