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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.
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.
Basic map elements
DITA maps are built from a few core elements that are used for referencing and organizing topics. The <topicmeta> element is also available to specify metadata for the map, for individual topics, or for groups of topics. Many elements inside <topicmeta> are also available inside the topic prolog.
<relheader>
The <relheader> element is a row in a relationship table that contains column definitions (<relcolspec> elements). Each table can have only one set of column definitions.

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.
  - Basic map elements
    DITA maps are built from a few core elements that are used for referencing and organizing topics. The <topicmeta> element is also available to specify metadata for the map, for individual topics, or for groups of topics. Many elements inside <topicmeta> are also available inside the topic prolog.
    - <map>
      The <map> element describes the relationships among a set of resources, such as DITA topics. Maps consist of references to topics, maps, and other resources organized into hierarchies, groups, and tables. Maps express these relationships in a single common format that can be used for different outputs.
    - <topicref>
      The <topicref> element identifies a topic (such as a concept, task, or reference) or other resource. A <topicref> can contain other <topicref> elements, allowing you to express navigation or table-of-contents hierarchies, as well as implying relationships between a containing (parent) <topicref> and its children. You can set the collection type of a parent <topicref> to determine how its children are related to each other. You can also express relationships among <topicref> elements by using group and table structures (such as <topicgroup> and <reltable>). Relationships are expressed as links in the output; by default, each participant in a relationship has links to the other participants in that relationship.
    - <topicmeta>
      The <topicmeta> element defines the metadata that applies to a topic when it appears in a map. When appropriate, that metadata also applies to the other topics in the map that are contained by the same element that contains the <topicmeta> element. When creating links, <topicmeta> content can also be used to override the title and short description that are used for the link. In addition, it can be used to add index entries to referenced content using the <keywords> element.
    - <anchor>
      The <anchor> element provides an integration point that another map can reference in order to insert its navigation into the referenced map's navigation tree. For those familiar with Eclipse help systems, this serves the same purpose as the <anchor> element in that system. It might not be supported for all output formats.
    - <navref>
      The <navref> element represents a pointer to another map which is preserved as a transcluding link in the result deliverable rather than resolved when the deliverable is produced. Output formats that support such linking can integrate the referenced resource when displaying the referencing map to an end user.
    - <reltable>
      The <reltable> element is a relationship table that specifies relationships among topics, based on the familiar table model of rows (<relrow>), columns (<relheader>), and cells (<relcell>).
    - <relrow>
      The <relrow> element defines a row in the relationship table (<reltable>). It creates a relationship between the cells in the row, which is expressed in output as links between the topics or resources referenced in those cells.
    - <relcell>
      The <relcell> element defines a cell in the relationship table (<reltable>). The <topicref> elements that it contains are related to the <topicref> elements in other cells of the same row. By default, topics or resources that are referenced in the same cell are not related to each other, unless you change the @collection-type attribute of the <relcell> to indicate that they are related.
    - <relheader>
      The <relheader> element is a row in a relationship table that contains column definitions (<relcolspec> elements). Each table can have only one set of column definitions.
    - <relcolspec>
      The <relcolspec> element is used to define a column in a relationship table. The <relcolspec> element can be used to set default attribute values for the <topicref> elements in the column.
    - <ux-window>
      Use the <ux-window> element to provide specifications for a window or viewport in which a user assistance topic or Web page can be displayed. The window or viewport can be referenced by the <resourceid> element associated with a topic or <topicref> element.
  - Map group elements
    The map group domain elements define, group, or reference content. Many of the map group elements are convenience elements, which means that they simply make it easier for an author to make use of existing functions.
- 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.
- 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.

`<relheader>`

The <relheader> element is a row in a relationship table that contains column definitions (<relcolspec> elements). Each table can have only one set of column definitions.

Content models

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

Inheritance

- map/relheader

Example

See reltable.

Attributes

The following attributes are available on this element: Universal attribute group.