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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.
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.
Highlighting elements
The highlighting elements are used to highlight text with styles (such as bold, italic, and monospace). Never use these elements when a semantically specific element is available. These elements are not intended for use by specializers, and are intended solely for use by authors when no semantically appropriate element is available and a formatting effect is required.
<sub>
The <sub> element indicates that text should appear with subscript highlighting, or placed lower in relationship to the surrounding text. Subscripted text is often a smaller font than the surrounding text. Formatting might vary depending on your output process. This element is part of the highlighting domain. Use this element only when a more semantically appropriate element is not available.

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.
  - Hazard statement elements
    The hazard statement domain elements are used to provide information about product safety hazards. The domain can be included in any topic type or map. Its elements are used to inform readers about potential hazards, consequences, and avoidance strategies.
  - Highlighting elements
    The highlighting elements are used to highlight text with styles (such as bold, italic, and monospace). Never use these elements when a semantically specific element is available. These elements are not intended for use by specializers, and are intended solely for use by authors when no semantically appropriate element is available and a formatting effect is required.
    - <b>
      The <b> element is typically used to apply bold highlighting to the content of the element. This element is part of the highlighting domain. Use this element only when a more semantically appropriate element is not available. For example, for specific items such as GUI controls, use the <uicontrol> element.
    - <i>
      The <i> element is typically used to apply italic highlighting to the content of the element. This element is part of the highlighting domain. Use this element only when a more semantically appropriate element is not available. For example, for specific items such as citations, use the <cite> element.
    - <sup>
      The <sup> element indicates that text should appear with superscript highlighting, or vertically raised in relationship to the surrounding text. Superscripts are usually a smaller font than the surrounding text. This element is part of the highlighting domain. Use this element only when a more semantically appropriate element is not available.
    - <sub>
      The <sub> element indicates that text should appear with subscript highlighting, or placed lower in relationship to the surrounding text. Subscripted text is often a smaller font than the surrounding text. Formatting might vary depending on your output process. This element is part of the highlighting domain. Use this element only when a more semantically appropriate element is not available.
    - <tt>
      The <tt> (teletype) element is typically used to apply monospaced highlighting to the content of the element. This element is part of the highlighting domain. Use this element only when a more semantically appropriate element is not available. For example, for specific items such as inline code fragments, use the <codeph> element.
    - <u>
      The <u> element is typically used to apply underline highlighting to the content of the element. This element is part of the highlighting domain. Use this element only when a more semantically appropriate element is not available. For example, for specific items such as GUI controls, use the <uicontrol> element.
    - <line-through>
      The <line-through> element indicates text that is rendered with a line struck through the content. This element is designed to enable authors to indicate a deletion or revision for rhetorical purpose; it is not intended to be used for indicating revisions. This element is part of the highlighting domain. Use this element only when a more semantically appropriate element is not available.
    - <overline>
      The <overline> element indicates content that is rendered with a line above it. This element is part of the highlighting domain. Use this element only when a more semantically appropriate element is not available.
  - Utilities elements
    The utilities domain elements represent common features of a language that might not necessarily be semantic, such as image maps.
  - DITAVAL reference domain
    The DITAVAL reference domain is used to reference a DITAVAL file that contains conditions that apply only to a subset of a DITA map. It also can be used to replicate a subset of a DITA map for multiple audiences.
- 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.

`<sub>`

The <sub> element indicates that text should appear with subscript highlighting, or placed lower in relationship to the surrounding text. Subscripted text is often a smaller font than the surrounding text. Formatting might vary depending on your output process. This element is part of the highlighting domain. Use this element only when a more semantically appropriate element is not available.

Note: Style sheets can be used to format the <sub> element differently, just like any other element can be restyled. Thus, it is not the case that content in <sub> elements will necessarily be rendered as subscript.

Content models

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

Inheritance

+ topic/ph hi-d/sub

Example

<p>The power produced by the electrohydraulic dam was 10<sup>10</sup> more than 
the older electric plant.  The difference was H<sub>2</sub>O.</p>

Attributes

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