Darwin Information Typing Architecture (DITA) Version 1.3 Part 1: Base Edition

OASIS DITA Technical Committee

The subjectdef element defines a subject (also known as a controlled value) within a subject scheme. The keys attribute specified on the subjectdef element assigns a key to the subject. A subject with a key can be addressed using a keyref attribute.

The subjectdef also can use a navtitle element to supply a label for the subject or the href attribute to reference a topic that captures the consensus definition for the subject.

As with normal topicref processing, when the subjectdef element specifies a navtitle and refers to a topic, processors should use the actual topic title in place of the navtitle. To use the navtitle as a subject label, set the locktitle attribute on the subjectdef element to "yes".

Content models

See appendix for information about this element in OASIS document type shells.


- map/topicref subjectScheme/subjectdef


  <!-- Pull in a scheme that defines unix OS values -->
  <schemeref href="unixOS.ditamap"/>
  <!-- Define new OS values that are merged with those in the unixOS scheme -->
  <subjectdef keys="os">
    <subjectdef keys="linux"/>
    <subjectdef keys="mswin"/>
    <subjectdef keys="zos"/>
  <!-- Define application values -->
  <subjectdef keys="app" navtitle="Applications">
    <subjectdef keys="apacheserv" href="subject/apache.dita"/>
    <subjectdef keys="mysql"      href="subject/sql.dita"/>

  <!-- Define an enumeration of the platform attribute, equal to
       each value in the OS subject. This makes the following values
       valid for the platform attribute: linux, mswin, zos -->
    <attributedef name="platform"/>
    <subjectdef keyref="os"/>
  <!-- Define an enumeration of the otherprops attribute, equal to
       each value in the application subjects.
       This makes the following values valid for the otherprops attribute:
       apacheserv, mysql -->
    <attributedef name="otherprops"/>
    <subjectdef keyref="app"/>


The following attributes are available on this element: Universal attribute group, Topicref element attributes group, Link relationship attribute group (with a narrowed definition of href, given below), outputclass, keys, and keyref. This element also uses processing-role, toc, collection-type, linking, and locktitle from Attributes common to many map elements.
A pointer to the resource represented by the topicref. See The href attribute for detailed information on supported values and processing implications. References to DITA content cannot be below the topic level: that is, you cannot reference individual elements inside a topic. References to content other than DITA topics should use the format attribute to identify the kind of resource being referenced.