XSD: If element has a specific value, another should be optional

Question

I have an XML document which is like:

<?xml version="1.0" encoding="UTF-8"?>
<html2filename xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../xsd/mapper.xsd">
    <htmlFile filename="N5670A">
        <variant>1</variant>
        <groups>
            <group>
                <name>Removing thermostat</name>
            </group>
            <someOtherElements>asdasd</someOtherElements>
        </groups>
    </htmlFile>
</html2filename>

Now element "groups" -> "group" -> "name" -> should have one constraint: It should be optional if "variant" has the value 3. If not it should be required.

Can XSD handle that? If yes, how?

Answer 1

XSD 1.1

An xs:assert can implement such a value-sensitive constraint:

            <xs:assert test="(variant = 3) or groups/group/name"/>

Here it is in the context of a complete XSD that will validate the XML you provided:

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema attributeFormDefault="unqualified" elementFormDefault="qualified" 
  xmlns:xs="http://www.w3.org/2001/XMLSchema"
  xmlns:vc="http://www.w3.org/2007/XMLSchema-versioning"
  vc:minVersion="1.1">
  <xs:element  name="html2filename">
    <xs:complexType>
      <xs:sequence>
        <xs:element name="htmlFile">
          <xs:complexType>
            <xs:sequence>
              <xs:element name="variant"/>
              <xs:element name="groups">
                <xs:complexType>
                  <xs:sequence>
                    <xs:element name="group" maxOccurs="unbounded">
                      <xs:complexType>
                        <xs:sequence>
                          <xs:element name="name" minOccurs="0"/>
                        </xs:sequence>
                      </xs:complexType>
                    </xs:element>
                    <xs:element name="someOtherElements"/>
                  </xs:sequence>
                </xs:complexType>
              </xs:element>
            </xs:sequence>
            <xs:attribute name="filename"/>
            <xs:assert test="(variant = 3) or groups/group/name"/>
          </xs:complexType>
        </xs:element>
      </xs:sequence>
     </xs:complexType>    
  </xs:element>
</xs:schema>