Having XML validation issues depending on the XML Parser used…how do I represent the constraint to be universally accepted

Question

I have a strange situation that has me perplexed a bit....

I have an XML data file I am trying to validate against a schema that seems to give different results depending on the parsers used. Not sure what I am doing wrong or how to better represent the constraints in the schema so that all the parsers can properly validate the XML.... Here is a snippet of the problem portion of the Schema:

<xsd:element name="DemoValues">
<xsd:annotation>
  <xsd:documentation>Demo values for any, or all, of the demo categories defined on the GAP . A
    demo value includes a reference to the category it applies to, a value in the appropriate
    format and an optional market reference if it is for a specific market. If the market
    reference is omitted the demo value applies to the entire area serviced by the outlet. Each
    demo category may only have a single demo value within this group of demo values. However if
    the demo value is for a market, there may be a demo value per market within this group of
    demo values. </xsd:documentation>
</xsd:annotation>
<xsd:complexType>
  <xsd:sequence>
    <xsd:element name="DemoValue" type="gap:demoValueType" maxOccurs="unbounded"/>
  </xsd:sequence>
</xsd:complexType>
<xsd:unique name="DemoValueConstraint">
  <xsd:annotation>
    <xsd:documentation>Constraint allows only up to one demo value for a demo category, and per
      market when a market reference exists. </xsd:documentation>
  </xsd:annotation>
  <xsd:selector xpath="gap:DemoValue"/>
  <xsd:field xpath="@demoRef"/>
  <xsd:field xpath="@marketRef|@demoRef"/>
</xsd:unique>

Here is the offending XML:

<DemoValues>
          <DemoValue demoRef="DM0" marketRef="MKT1">0.40</DemoValue>
          <DemoValue demoRef="DM1">15.00</DemoValue>
</DemoValues>

Produces this error:

Element '{http://www.AAAA.org/schemas/canadianTVGAP}DemoValue', attribute 'marketRef': The XPath '@marketRef|@demoRef' of a field of unique identity-constraint '{http://www.AAAA.org/schemas/canadianTVGAP}DemoValueConstraint' evaluates to a node-set with more than one member.

Simplified Error is: The field ‘marketRef’ is expecting at the most one value.

The intent for the xml is to allow all these combinations:

1)

 <DemoValues>
          <DemoValue demoRef="DM0" marketRef="MKT1">0.40</DemoValue>
          <DemoValue demoRef="DM1">15.00</DemoValue>
 </DemoValues>

2)

<DemoValues>
          <DemoValue demoRef="DM0" marketRef="MKT1">0.40</DemoValue>
          <DemoValue demoRef="DM0" marketRef="MKT2">0.41</DemoValue>
          <DemoValue demoRef="DM0" marketRef="MKT3">0.42</DemoValue>
          <DemoValue demoRef="DM0" marketRef="MKT4">0.43</DemoValue>
          <DemoValue demoRef="DM1">15.00</DemoValue>
</DemoValues>

3)

<DemoValues>
          <DemoValue demoRef="DM0" marketRef="MKT1">0.40</DemoValue>
          <DemoValue demoRef="DM1" marketRef="MKT1">0.41</DemoValue>
          <DemoValue demoRef="DM2" marketRef="MKT1">0.42</DemoValue>
          <DemoValue demoRef="DM3">15.00</DemoValue>
</DemoValues>

Thanks for any help!!

Answer 1

Do you need to use field here for some other reason than to restrict the attribute list to the combinations you describe?

An XML element can have, at most, one instance of any named attribute. This is a fact about XML, independent of schema.

In your definition of gap:demoValueType, simply specify the two attributes by using <xsd:attribute ... />. By the look of your examples, you probably want to use use="required" on the definition of @demoref)

Answer 2

I'm not surprised you are getting different results from different processors here, because the spec is very obscurely written. However, the union expression in your second xs:field is clearly wrong - you should never have a field that can select more than one node. I would expect it to work correctly if your first field is @demoRef and your second is @marketRef, however, I've been re-reading the spec and I would hesitate to argue with an implementor who interpreted it differently.