XML Restrict based on another element value

Question

Basically I have my XML version 1.0 and I have a complex element with following example:

<tile>
  <position>5</position>
  <type>floor</type>
  <towerPlacement>true</towerPlacement>
</tile>

I have defined following in my XML Schema:

<xs:element name="type">
   <xs:simpleType>
   <xs:restriction base="xs:string">
   <xs:enumeration value="road"/>
   <xs:enumeration value="floor"/>
   <xs:enumeration value="startPos"/>
   <xs:enumeration value="endPos"/>
   </xs:restriction>
   </xs:simpleType>
</xs:element>

Is there a way to make my towerPlacement true only if type = floor?

<xs:element type="xs:boolean" name="towerPlacement" minOccurs="0" maxOccurs="1" />

Answer 1

XSD 1.0

Your constraint cannot be expressed in XSD 1.0.

XSD 1.1

Your constraint can be expressed in XSD 1.1 using an assertion to state that towerPlacement must only be true if type = 'floor':

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" 
           xmlns:vc="http://www.w3.org/2007/XMLSchema-versioning" 
           vc:minVersion="1.1">
  <xs:element name="tile">
    <xs:complexType>
      <xs:sequence>
        <xs:element name="position" type="xs:integer"/>
        <xs:element name="type">
          <xs:simpleType>
            <xs:restriction base="xs:string">
              <xs:enumeration value="road"/>
              <xs:enumeration value="floor"/>
              <xs:enumeration value="startPos"/>
              <xs:enumeration value="endPos"/>
            </xs:restriction>
          </xs:simpleType>
        </xs:element>
        <xs:element name="towerPlacement" type="xs:string"/>
      </xs:sequence>
      <xs:assert test="(type='floor' and towerPlacement='true') 
                       or towerPlacement!='true'"/>
    </xs:complexType>
  </xs:element>
</xs:schema>