Example: Constrain attributes for the <section> element using RNG

Example

This section is non-normative.

1. The DITA architect creates a constraint module: id-requiredSectionContraintMod.rng.
2. They update the catalog.xml file to include the new constraint module.
3. They add the following content to the constraint module:

   <?xml version="1.0" encoding="UTF-8"?>
   <grammar 
     xmlns="http://relaxng.org/ns/structure/1.0"
     xmlns:dita="http://dita.oasis-open.org/architecture/2005/"
     xmlns:a="http://relaxng.org/ns/compatibility/annotations/1.0"
     datatypeLibrary="http://www.w3.org/2001/XMLSchema-datatypes">
   
     <div>
       <a:documentation>ATTRIBUTE LIST OVERRIDES</a:documentation>
       <include href="urn:pubid:oasis:names:tc:dita:rng:topicMod.rng:2.0">      
         <define name="section.attributes">
             <attribute name="id">
               <data type="NMTOKEN"/>
             </attribute>        
           <ref name="conref-atts"/>
           <ref name="select-atts"/>
           <ref name="localization-atts"/>
           <optional>
             <attribute name="outputclass"/>
           </optional>
         </define>
       </include>
     </div>
   
   </grammar>  

   Note that unlike a constraint module that is implemented using DTD, this constraint module did not need to re-declare the patterns that are referenced in the redefinition of the content model for <section>

4. They then integrate the constraint module into the document-type shell for topic by adding an <include> element in the "CONTENT CONSTRAINT INTEGRATION" section:

   <div>
     <a:documentation>CONTENT CONSTRAINT INTEGRATION</a:documentation>
     <include href="id-requiredSectionConstraintMod.rng"/>
   </div>

5. They then remove the <include> statement that references topicMod.rng from the "MODULE INCLUSIONS" section:

   <div>
     <a:documentation>MODULE INCLUSIONS </a:documentation>
       <include href="urn:pubid:oasis:names:tc:dita:rng:topicMod.rng:2.0"/>
       <include href="urn:pubid:oasis:names:tc:dita:rng:audienceAttDomain.rng:2.0"/>
       <include href="urn:pubid:oasis:names:tc:dita:rng:deliveryTargetAttDomain.rng:2.0"/>
       <include href="urn:pubid:oasis:names:tc:dita:rng:platformAttDomain.rng:2.0"/>
       <include href="urn:pubid:oasis:names:tc:dita:rng:productAttDomain.rng:2.0"/>
       <include href="urn:pubid:oasis:names:tc:dita:rng:otherpropsAttDomain.rng:2.0"/>
       <include href="urn:pubid:oasis:names:tc:dita:rng:highlightDomain.rng:2.0"/>
     </div>

6. They check their test topic to ensure that the content model is modified as expected.