RELAX NG

Mixed Content Models with Order

You have seen that a pattern interleaved with a group is allowed to appear anywhere between the patterns of the group. This feature may be used with a text pattern to define ordered mixed-content models, in which the text nodes may appear anywhere but the order of the elements is fixed. These content models are quite unusual in XML. A use case might be a data-oriented vocabulary such as our library, in which optional text can be inserted to provide more user-friendly documentation:

<character id="Lucy">
 <name>Lucy</name> made her first apparition in a Peanuts strip on
 <born>1952-03-03</born>, and the least we can say about her is that she is
 <qualification>bossy, crabby and selfish</qualification>.
</character>

If you want to fix the order of the child elements, just embed a group pattern inside a mixed pattern:

<!--This schema is INVALID-->
<element name="character">
  <mixed>
   <attribute name="id"/>
   <group>
     <element name="name">
       <text/>
     </element>
     <element name="born">
       <text/>
     </element>
     <element name="qualification">
      <text/>
     </element>
    </group>
   </mixed>
  </element>

Per the definition of the mixed pattern, this is equivalent to:

#This schema is invalid
<element name="character">
 <interleave>
  <attribute name="id"/>
  <text/>
  <group>
   <element name="name">
     <text/>
   </element>
   <element name="born">
     <text/>
   </element>
   <element name="qualification">
    <text/>
   </element>
  </group>
 </interleave>
</element>

The text pattern matches text nodes before, after, or between the ...