How can I validate one element based off of another element in XSD?

Question

I have this XML:

    <record>
      <element>
        <freeText>There is a big red cow.</freeText>
        <terms>
          <term>big</term>
          <term>red</term>
        <term>
      </element>
      <element>
        <freeText>Technically this is irrelevant but I wanted to figure out if this assertion conflicts somehow.</freeText>
        <terms>
          <term>farm</term>
          <term>animal</term>
        </terms>
       </element>
    </record>   

What I would like to do is create an assertion that if the freeText field contains "cow", then one of the terms must also be "cow".

The relevant XSD I have is this:

<xs:element name ="terms">
  <xs:complexType>
   <xs:sequence>
    <xs:element maxOccurs="unbounded" ref="term"/>
   </xs:sequence>
   <xs:assert test = "if (contains(../description,'cow') = true()) then (../terms/term = 'cow') else (term = *)"/>
   <xs:assert text = "if (term = 'farm') then (term = 'animal') else (term = *)"/>
  </xs:complexType>
</xs:element>

No matter how I write my xpath, I can't figure out how to get the first assertion to validate properly. The second assertion works fine, I have a bunch of terms with one-way co-occurrence constraints, and I've never had a problem with that. But with the assertion that checks freeText it doesn't seem to be looking in the right places. Would appreciate some help.

Answer 1

There's an absolute context rule that an assert can only look within the SUBTREE of the element on which it is defined. That's why you cannot use navigation up, i.e. contains(../description,'cow')

Please try the following solution.

Input XML

<record>
    <element>
        <freeText>There is a big red cow.</freeText>
        <terms>
            <term>big</term>
            <term>small</term>
        </terms>
    </element>
    <element>
        <freeText>Technically this is irrelevant but I wanted to figure out if this assertion conflicts somehow.</freeText>
        <terms>
            <term>farm</term>
            <term>animal</term>
        </terms>
    </element>
</record>

XSD 1.1

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified">
  <xs:element name="record">
    <xs:complexType>
      <xs:sequence>
        <xs:element maxOccurs="unbounded" ref="element"/>
      </xs:sequence>
    </xs:complexType>
  </xs:element>
  <xs:element name="element">
    <xs:complexType>
      <xs:sequence>
        <xs:element ref="freeText"/>
        <xs:element ref="terms"/>
      </xs:sequence>
      <xs:assert test = "if (not(contains(freeText,'cow'))) then true() else 
        terms/term[. = 'cow']"/>
    </xs:complexType>
  </xs:element>
  <xs:element name="freeText" type="xs:string"/>
  <xs:element name="terms">
    <xs:complexType>
      <xs:sequence>
        <xs:element maxOccurs="unbounded" ref="term"/>
      </xs:sequence>
    </xs:complexType>
  </xs:element>
  <xs:element name="term" type="xs:NCName"/>
</xs:schema>