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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.
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.
<index-base>
The <index-base> element allows indexing extensions to be added by specializing this element.

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.
- 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.
  - <boolean>
    The <boolean> element was deprecated in DITA version 1.1. It was originally intended to express one of two opposite values, such as yes / no or on / off.
  - <data>
    The <data> element represents a property within a DITA topic or map. While the <data> element can be used directly to capture properties, it is particularly useful as a basis for specialization. Default processing should treat the content as an unknown kind of metadata and ignore it for rendering, but custom processing might match the @name attribute or specialized element and use the element for automated manipulation or to format data associated with the body flow. For example, a specialized <data> element might be used to format properties as sidebars or other adornments or to harvest properties for automated processing.
  - <data-about>
    The <data-about> element identifies the subject of a property when the subject isn't associated with the context in which the property is specified. The property itself is expressed by the <data> element. The <data-about> element handles exception cases where a property must be expressed somewhere other than inside the actual subject of the property. The <data-about> element is particularly useful as a basis for specialization in combination with the <data> element.
  - <foreign>
    The <foreign> element allows the introduction of non-DITA content, for example, MathML, SVG, or Rich Text Format (RTF). The <foreign> element or a specialization can contain more than one type of non-DITA content or a mix of DITA and non-DITA content. Specialization of the <foreign> element generally is implemented as a domain, but architects looking for more control over the content can implement foreign vocabularies as structural specializations.
  - <index-base>
    The <index-base> element allows indexing extensions to be added by specializing this element.
  - <itemgroup>
    The <itemgroup> element can be used to sub-divide or organize elements that occur inside a list item, definition, or parameter definition.
  - <no-topic-nesting>
    The <no-topic-nesting> element is a placeholder in the DITA architecture. It is not actually used by the default DITA document types; it is for use only when creating a validly customized document type where the information designer wants to eliminate the ability to nest topics. Not intended for use by authors, and has no associated output processing.
  - <state>
    The <state> element specifies a name/value pair whenever it is necessary to represent a named state that has a variable value. The element is primarily intended for use in specializations to represent specific states (like logic circuit states, chemical reaction states, airplane instrumentation states, and so forth).
  - <unknown>
    The <unknown> element is an open extension that allows information architects to incorporate xml fragments that do not necessarily fit into an existing DITA use case. Processors should ignore this element unless otherwise instructed.
- 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.

`<index-base>`

The <index-base> element allows indexing extensions to be added by specializing this element.

The <index-base> element can only exist as a child of an <indexterm> element. This characteristic makes it the appropriate element to specialize to add indexing extensions. For example, the <index-see>, <index-see-also>, and <index-sort-as> elements only make sense as children of <indexterm> and so are specializations of <index-base>. Those elements are all part of the indexing domain.

On its own, <index-base> has no meaning. Processors should ignore this element and its content if encountered in its unspecialized form.

Content models

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

Inheritance

- topic/index-base

Example

This element is not intended to be used in source files.

The <index-see-also> element is specialized from <index-base>; see index-see-also for an example of how <index-base> can be used with specialization.

Attributes

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