DTD: Coding requirements for structural and element-domain modules

Module files

A vocabulary module that defines a structural or element-domain specialization is composed of two files:

Definition module file

This (.mod) file declares the element names, content models, and attribute lists for the element types that are defined in the vocabulary module.

Entity declaration file

This (.ent) file declares the general and parameter entities that are used to integrate the vocabulary module into a document-type shell.

Element definitions

A structural or element-domain vocabulary module contains a declaration for each element type that is named by the module. While the XML standard allows content models to refer to undeclared element types, the DITA standard does not permit this. All element types or attribute lists that are named within a vocabulary module are declared in one of the following objects:

• The vocabulary module
• A base module of which the vocabulary module is a direct or indirect specialization
• (For structural modules) A required domain module

The following components make up a single element definition in a DITA DTD-based vocabulary module.

Element name entities

For each element type, there is a parameter entity with a name that matches the element-type name. The value is the element-type name.

Example

This section is non-normative.

For example:

<!ENTITY % topichead "topichead">

The parameter entity provides a layer of abstraction when setting up content models. It can be redefined in a document-type shell in order to create domain extensions or implement element configuration (constraint and expansion).

Element name entities for a vocabulary module typically are grouped together at the top of the vocabulary module. They can occur in any order.

Content-model parameter entity

For each element type, there is a parameter entity that defines the content model. The name of the parameter entity is tagname.content, and the value is the content model definition.

Example

This section is non-normative.

For example:

<!ENTITY % topichead.content
  "((%topicmeta;)?, 
    (%data.elements.incl; | 
     %navref; | 
     %topicref;)*)
">

Attribute-list parameter entity

For each element type, there is a parameter entity that declares the attributes that are available on the element. The name of the parameter entity is tagname.attributes, and the value is a list of the attributes that are used by the element type (except for @class).

Example

This section is non-normative.

For example:

<!ENTITY % topichead.attributes
 "keys CDATA #IMPLIED
  %topicref-atts;
  %univ-atts;"
>

Consistent use and naming of the tagname.content parameter entity enables the use of element-configuration modules (constraint and expansion) to redefine the content model.

Element declaration

For each element type, there is an element declaration that consists of a reference to the content-model parameter entity.

Example

This section is non-normative.

For example:

<!ELEMENT topichead    %topichead.content;>

Attribute list declaration

For each element type, there is an attribute-list declaration that consists of a reference to the attribute-list parameter entity.

Example

This section is non-normative.

For example:

<!ATTLIST topichead    %topichead.attributes;>

Specialization attribute declarations

A vocabulary module defines a @class attribute for every element that is declared in the module. The value of the attribute is constructed according to the rules in The class attribute rules and syntax.

Example

This section is non-normative.

For example, the ATTLIST definition for the <topichead> element (a specialization of the <topicref> element in the base map type) includes the definition of the @class attribute, as follows:

<!ATTLIST topichead  class CDATA "+ map/topicref  mapgroup-d/topichead ">

<!-- ============================================================= -->
<!--                   ELEMENT NAME ENTITIES                       -->
<!-- ============================================================= -->

<!ENTITY % topichead      "topichead"                                   >

...

<!-- ============================================================= -->
<!--                    ELEMENT DECLARATIONS                       -->
<!-- ============================================================= -->

<!--                    LONG NAME: Topichead                       -->
<!ENTITY % topichead.content
                       "((%topicmeta;)?,
                         (%data.elements.incl; |
                          %navref; |
                          %topicref;)*)"
>
<!ENTITY % topichead.attributes
              "keys
                          CDATA
                                    #IMPLIED
               %topicref-atts;
               %univ-atts;"
>
<!ELEMENT  topichead %topichead.content;>
<!ATTLIST  topichead %topichead.attributes;>

...

<!-- ============================================================= -->
<!--             SPECIALIZATION ATTRIBUTE DECLARATIONS             -->
<!-- ============================================================= -->
  
...

<!ATTLIST  topichead      class CDATA "+ map/topicref mapgroup-d/topichead ">

<!-- ================== End of DITA Map Group Domain ==================== -->