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Language reference: All-inclusive edition
The language reference portion of the DITA specification contains a topic for each DITA element. The topic defines the element, its inheritance hierarchy, and provides examples of usage. This portion of the DITA specification also includes information about DITA attributes.
Classification elements
Classification elements support managing metadata. Those in the subject scheme map are used to define controlled values and to bind the controlled values to DITA attributes as enumerations. Those declared in the classification domain are used in other maps to classify content according to the scheme.
Classification domain elements
The classification domain elements are used to identify the subject matter of content that is referenced in a map. These subjects must be subjects defined in a subject scheme map. In particular, this allows an author to classify content in new subject categories that are not bound to existing metadata attributes.

Specification URIs
Notices
Introduction to DITA 1.3
The Darwin Information Typing Architecture (DITA) specification defines a set of document types for authoring and organizing topic-oriented information, as well as a set of mechanisms for combining, extending, and constraining document types.
Architectural specification: All-inclusive edition
The architectural specification portion of the DITA specification outlines the framework of DITA. It contains an overview of DITA markup; addressing; processing; configuration, specialization, generalization, and constraints; as well as information about coding DITA grammar files.
Language reference: All-inclusive edition
The language reference portion of the DITA specification contains a topic for each DITA element. The topic defines the element, its inheritance hierarchy, and provides examples of usage. This portion of the DITA specification also includes information about DITA attributes.
- Element quick reference
  This section contains a listing of DITA elements.
- Topic elements
  The base topic elements include elements that make up the core building blocks of the DITA topic, such as topic, body, and related-links, as well as elements like <p> and <ph> that are used in many topic specializations. Some of these elements are also available inside the <topicmeta> map element.
- Map elements
  Map elements include the core components of DITA maps, such as <topicref> and <reltable>, as well as general purpose map specializations in the map group domain.
- Metadata elements
  Metadata elements include information that is located within the <topicmeta> element (in maps) or <prolog> element (in topics), as well as indexing elements that can be placed in additional locations within topic content.
- Domain elements
  General purpose domains are not specific to any type of information, such as the hazard statement domain that provides elements for describing hazardous situations.
- Classification elements
  Classification elements support managing metadata. Those in the subject scheme map are used to define controlled values and to bind the controlled values to DITA attributes as enumerations. Those declared in the classification domain are used in other maps to classify content according to the scheme.
  - Subject scheme elements
    Subject scheme maps are used to define sets of controlled values and taxonomic subjects; bind controlled values to attributes; and specify relationships among taxonomic subjects.
  - Classification domain elements
    The classification domain elements are used to identify the subject matter of content that is referenced in a map. These subjects must be subjects defined in a subject scheme map. In particular, this allows an author to classify content in new subject categories that are not bound to existing metadata attributes.
    - <subjectref>
      The <subjectref> element identifies a subject to classify content. The <subjectref> can identify the subject with a @keyref attribute (if the scheme has a <subjectdef> with a @keys attribute that assigns a key to the subject) or an @href attribute (if the scheme is not available and a topic exists that defines the subject).
    - <topicapply>
      The <topicapply> element identifies subjects that qualify the content for filtering or flagging but not retrieval. The <topicapply> element can identify a single subject. Additional subjects can be specified by nested <subjectref> elements.
    - <topicsubject>
      The <topicsubject> element identifies the subjects covered by a topic or map.
    - <topicSubjectTable>
      The <topicSubjectTable> element is a specialized relationship table which allows a map to use relationship tables to associate topics with subjects. Tools (such as search tools) might use these classifications to retrieve content that is relative to a specific subject or combination of subjects.
    - <topicSubjectHeader>
      The <topicSubjectHeader> element specifies constraints on the subjects used in classifications.
    - <topicSubjectRow>
      The <topicSubjectRow> is a grouping element that contains one row of a subject table. It contains topic references in the first column, and relates those references to the subjects in each following column.
    - <topicCell>
      The <topicCell> element contains topics that will be associated with subjects in each following column of the current row in the <topicSubjectTable>.
    - <subjectCell>
      The <subjectCell> element contains subjects that are associated with topics in the first column of the current row in the <topicSubjectTable>. The subjects themselves have no defined relationship across columns, other than the fact that they apply to the same content.
- Specialization elements
  Several DITA elements exist either for architectural reasons or for support of specialized markup yet to be designed. Although there is little need to use these elements unless you are directed to, some of them, such as <state>, can be used if your content makes use of these semantic distinctions. For example, a discussion of signals on a gate of an integrated logic circuit might use the <state> element to represent either on or off conditions of that gate.
- Legacy conversion elements
  Conversion elements exist primarily to aid in the conversion of content to DITA.
- DITAVAL elements
  A conditional processing profile (DITAVAL file) is used to identify which values are to be used for conditional processing during a particular output, build, or some other purpose. The profile should have an extension of .ditaval.
- Technical content elements
  Elements in the technical content section include the original Concept, Task, and Reference specializations, as well as specializations added in later releases. It also includes domains designed primarily for technical content.
- Learning and training elements
  Elements in the learning and training section include specialized topics, maps, content, and metadata elements specially designed to support instructional content.
- Attributes
  This section collects commonly used attributes, with common definitions. If an element uses a different definition, or narrows the scope of, an otherwise common attribute, it will be called out in the topic that defines the element.
Conformance
Conformance to the DITA specification allows documents and document types that are used with different processors or different versions of a processor to produce the same or similar results with little or no reimplementation or modification.
Acknowledgments
(Non-normative) Many members of the OASIS DITA Technical Committee participated in the creation of this specification and are gratefully acknowledged.
Non-normative information
This section contains non-normative information, including topics about new features in DITA 1.3 and migrating from DITA 1.2 to DITA 1.3.
Content models for learning and training package
For each element in the learning and training package, this section presents the content model and a list of parent elements that can contain that element.

Classification domain elements

The classification domain elements are used to identify the subject matter of content that is referenced in a map. These subjects must be subjects defined in a subject scheme map. In particular, this allows an author to classify content in new subject categories that are not bound to existing metadata attributes.