DTD: Coding requirements for element-configuration modules

This section is non-normative.

Element-configuration modules (constraint and expansion) have specific coding requirements.

The `tagname.attributes` parameter entity

When the attribute list for an element is constrained or expanded, there is a declaration of the tagname.attributes parameter entity that defines the modified attributes.

Example

This section is non-normative.

The following list provides examples for both constraint and expansion modules:

Constraint module

The following parameter entity defines a constrained attributes list for the <note> element that removes most of the values defined for @type. It also removes @othertype:

<!ENTITY % note.attributes  
       "type  (attention | caution | note ) #IMPLIED
        %univ-atts;">

The following parameter entity restricts the highlighting domain to <b> and <i>:


<!ENTITY % HighlightingDomain-c-ph     "b | i"  >

Expansion module

The following parameter entity defines a new attribute intended for use with various table elements:

<!ENTITY % cellPurposeAtt-d-attribute-expansion
  "cell-purpose  (sale | out-of-stock | new | last-chance | inherit | none)  #IMPLIED"
>

For expansion modules, note the following considerations. The tagname.attributes parameter entity can be defined in an attribute-specialization module, or it can be defined directly in the expansion module.

The `tagname.content` parameter entity

When the content model for an element is constrained or expanded, there is a declaration of the tagname.content parameter entity that defines the modified content model.

Example

This section is non-normative.

The following list provides examples for both constraint and expansion modules:

Constraint module

The following parameter entity defines a more restricted content model for <topic>, in which the <shortdesc> element is required.

<!ENTITY % topic.content 
  "((%title;),
    (%shortdesc;), 
    (%prolog;)?, 
    (%body;)?, 
    (%topic-info-types;)*)"
>

Note that replacing a base element with domain extensions is a form of constraint that can be accomplished directly in the document-type shell. No constraint module is required.

In the following example, the <pre> base type is removed from the entity declaration, effectively allowing specializations of <pre> but not <pre> itself.

<!ENTITY % pre
    "%pr-d-pre; | 
     %sw-d-pre; | 
     %ui-d-pre;">

Expansion module

The redefinition of the content model references the parameter entity that was defined in the element-specialization module.

The following code sample shows the entity declaration file for an element-specialization module that defines a <section-shortdesc> element, which is intended to be added to the content model of <section>:

<!ENTITY % section-shortdesc "section-shortdesc">

When the content model for <section> is redefined in the expansion module, it references the parameter entity defined in the entities file for the element specialization:


<!ENTITY % section.content
              "(#PCDATA |
               %dl; |
               %div; |
               %fig; |
               %image; |
               %note; |
               %ol; |
               %p; |
               %simpletable; |
               %ul; |
               %title; |
               %draft-comment;|
               %sectionShortdesc;)*"
>

Note that this expansion module also constrains the content model of <section> to only include certain block elements.