RELAX NG: Coding requirements for structural modules

Required topic and map element attributes

The topic or map element type references the arch-atts pattern, which defines the @DITAArchVersion attribute in the DITA architecture namespace and sets the attribute to the version of DITA. In addition, the topic or map element type references the specializations-att pattern, which pulls in a definition for the @specializations attribute.

<div>
  <a:documentation> LONG NAME: Concept </a:documentation>
  <!-- ... -->
  <define name="concept.attlist" combine="interleave">
    <ref name="concept.attributes"/>
    <ref name="arch-atts"/>
    <ref name="specializations-att"/>
  </define>
  <!-- ... -->
</div>

The @DITAArchVersion and @specializations attributes give processors a reliable way to check the DITA version and the attribute domains that are used.

Controlling nesting in topic types

A structural module that defines a new topic type typically defines an info-types style pattern to specify a default for what topic types are permitted to nest. Document-type shells then can control how topics are allowed to nest by redefining the pattern.

The following rules apply when using a pattern to control topic nesting.

Pattern name

The pattern name is the topic element name plus the suffix -info-types.

For example, the info-types pattern for the concept topic type is concept-info-types.

Pattern value

To set up default topic-nesting rules, set the pattern to the desired topic elements. The default topic nesting is used when a document-type shell does not set up different rules.

For example:

<div>
  <a:documentation>INFO TYPES PATTERNS</a:documentation>
  <define name="mytopic-info-types">
    <ref name="subtopictype-01.element"/>
    <ref name="subtopictype-02.element"/>
  </define>
  <!-- ... -->
</div>

To disable topic nesting, specify the <empty> element.

For example:

<define name="learningAssessment-info-types">
  <empty/>
</define>

The info-types pattern also can be used to refer to common nesting rules across the document-type shell.

For example:

<div>
  <a:documentation>INFO TYPES PATTERNS</a:documentation>
  <define name="mytopic-info-types">
    <ref name="info-types"/>
  </define>
  <!-- ... -->
</div>

Content model of the root element

In the declaration of the root element of a topic type, the last position in the content model is the topictype-info-types pattern.

For example, the <concept> element places the pattern after <related-links>:

<div>
  <a:documentation>LONG NAME: Concept</a:documentation>
  <define name="concept.content">
    <!-- ... -->
    <optional>
      <ref name="related-links"/>
    </optional>
    <zeroOrMore>
      <ref name="concept-info-types"/>
    </zeroOrMore>
  </define>
</div>

In certain cases, you do not need to use the info-types pattern to control topic nesting:

• If a topic type will never permit topic nesting, regardless of context, it can be defined without any pattern or any nested topics.
• If a topic type will allow only specific nesting patterns, such as allowing only other topic types that are defined in the same module, it can nest those topics directly in the same way that other nested elements are defined.