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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.
DITA markup
Topics and maps are the basic building blocks of the Darwin Information Typing Architecture (DITA). Metadata attributes and values can be added to DITA topics and maps, as well as to elements within topics, to allow for conditional publishing and content reuse.
Subject scheme maps and their usage
Subject scheme maps can be used to define controlled values and subject definitions. The controlled values can be bound to attributes, as well as element and attribute pairs. The subject definitions can contain metadata and provide links to more detailed information; they can be used to classify content and provide semantics that can be used in taxonomies and ontologies.
Examples of subject scheme maps
This section contains examples and scenarios that illustrate the use of subject scheme maps.
Example: Extending a subject scheme
You can extend a subject scheme by creating another subject scheme map and referencing the original map using a <schemeref> element. This enables information architects to add new relationships to existing subjects and extend enumerations of controlled values.

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.
- Introduction to DITA
  The Darwin Information Typing Architecture (DITA) is an XML-based architecture for authoring, producing, and delivering topic-oriented, information-typed content that can be reused and single-sourced in a variety of ways. While DITA historically has been driven by the requirements of large-scale technical documentation authoring, management, and delivery, it is a standard that is applicable to any kind of publication or information that might be presented to readers, including interactive training and educational materials, standards, reports, business documents, trade books, travel and nature guides, and more.
- DITA markup
  Topics and maps are the basic building blocks of the Darwin Information Typing Architecture (DITA). Metadata attributes and values can be added to DITA topics and maps, as well as to elements within topics, to allow for conditional publishing and content reuse.
  - DITA topics
    DITA topics are the basic units of DITA content and the basic units of reuse. Each topic contains a single subject. Topics might be of specific specialized information types, such as task, concept, or reference, or they might be generic, that is, without a specified information type.
  - DITA maps
    This topic collection contains information about DITA maps and the purposes that they serve. It also includes high-level information about DITA map elements, attributes, and metadata.
  - Subject scheme maps and their usage
    Subject scheme maps can be used to define controlled values and subject definitions. The controlled values can be bound to attributes, as well as element and attribute pairs. The subject definitions can contain metadata and provide links to more detailed information; they can be used to classify content and provide semantics that can be used in taxonomies and ontologies.
    - Subject scheme maps
      Subject scheme maps use key definitions to define collections of controlled values and subject definitions.
    - Defining controlled values for attributes
      Subject scheme maps can define controlled values for DITA attributes without having to define specializations or constraints. The list of available values can be modified quickly to adapt to new situations.
    - Binding controlled values to an attribute
      The controlled values defined in a subject scheme map can be bound to an attribute or an element and attribute pair. This affects the expected behavior for processors and authoring tools.
    - Processing controlled attribute values
      An enumeration of controlled values can be defined with hierarchical levels by nesting subject definitions. This affects how processors perform filtering and flagging.
    - Extending subject schemes
      The <schemeref> element provides a mechanism for extending a subject scheme. This makes it possible to add new relationships to existing subjects and extend enumerations of controlled values.
    - Scaling a list of controlled values to define a taxonomy
      Optional classification elements make it possible to create a taxonomy from a list of controlled values.
    - Classification maps
      A classification map is a DITA map in which the classification domain has been made available.
    - Examples of subject scheme maps
      This section contains examples and scenarios that illustrate the use of subject scheme maps.
      - Example: How hierarchies defined in a subject scheme map affect filtering
        This scenario demonstrates how a processor evaluates attribute values when it performs conditional processing for an attribute that is bound to a set of controlled values.
      - Example: Extending a subject scheme
        You can extend a subject scheme by creating another subject scheme map and referencing the original map using a <schemeref> element. This enables information architects to add new relationships to existing subjects and extend enumerations of controlled values.
      - Example: Extending a subject scheme upwards
        You can broaden the scope of a subject category by creating a new subject scheme map that defines the original subject category as a child of a broader category.
      - Example: Defining values for @deliveryTarget
        You can use a subject scheme map to define the values for the @deliveryTarget attribute. This filtering attribute, which is new in DITA 1.3, is intended for use with a set of hierarchical, controlled values.
  - DITA metadata
    Metadata can be applied in both DITA topics and DITA maps. Metadata that is assigned in DITA topics can be supplemented or overridden by metadata that is assigned in a DITA map; this design facilitates the reuse of DITA topics in different DITA maps and use-specific contexts.
- DITA addressing
  DITA provides two addressing mechanisms. DITA addresses either are direct URI-based addresses, or they are indirect key-based addresses. Within DITA documents, individual elements are addressed by unique identifiers specified on the @id attribute. DITA defines two fragment-identifier syntaxes; one is the full fragment-identifier syntax, and the other is an abbreviated fragment-identifier syntax that can be used when addressing non-topic elements from within the same topic.
- DITA processing
  DITA processing is affected by a number of factors, including attributes that indicate the set of vocabulary and constraint modules on which a DITA document depends; navigation; linking; content reuse (using direct or indirect addressing); conditional processing; branch filtering; chunking; and more. In addition, translation of DITA content is expedited through the use of the @dir, @translate, and @xml:lang attributes, and the <index-sort-as> element.
- Configuration, specialization, generalization, and constraints
  The extension facilities of DITA allow existing vocabulary and constraint modules to be combined to create specific DITA document types. Vocabulary modules also can be specialized to meet requirements that are not satisfied by existing markup.
- Coding practices for DITA grammar files
  This section collects all of the rules for creating modular DTD, RELAX NG, or XML Schema grammar files to represent DITA document types, specializations, and constraints.
- Technical content specializations
  This section contains information about the technical content specializations. It includes a summary of the document types and domains, as well as information about how the technical content specializations support authoring troubleshooting information.
- Learning and training specializations
  The section contains information about the learning and training specializations: Challenges faced by developers of instructional content; use cases; objectives of the specializations; information about the reusable learning-objects approach to learning and training content; summary of the topic types and domains; and more.
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.
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.

Example: Extending a subject scheme

You can extend a subject scheme by creating another subject scheme map and referencing the original map using a <schemeref> element. This enables information architects to add new relationships to existing subjects and extend enumerations of controlled values.

A company uses a common subject scheme map (baseOS.ditamap) to set the values for the @platform attribute.

<subjectScheme>
  <subjectdef keys="os" navtitle="Operating system">
    <subjectdef keys="linux" navtitle="Linux">
      <subjectdef keys="redhat" navtitle="RedHat Linux"/>
      <subjectdef keys="suse" navtitle="SuSE Linux"/>
    </subjectdef>
    <subjectdef keys="windows" navtitle="Windows"/>
    <subjectdef keys="zos" navtitle="z/OS"/>
  </subjectdef>
  <enumerationdef>
    <attributedef name="platform"/>
    <subjectdef keyref="os"/>
  </enumerationdef>
</subjectScheme>

The following subject scheme map extends the enumeration defined in baseOS.ditamap. It adds "macos" as a child of the existing "os" subject; it also adds special versions of Windows as children of the existing "windows" subject:

<subjectScheme>
  <schemeref href="baseOS.ditamap"/>
  <subjectdef keyref="os">
    <subjectdef keys="macos" navtitle="Macintosh"/>
    <subjectdef keyref="windows">
      <subjectdef keys="winxp" navtitle="Windows XP"/>
      <subjectdef keys="winvis" navtitle="Windows Vista"/>
    </subjectdef>
  </subjectdef>
</subjectScheme>

Note that the references to the subjects that are defined in baseOS.ditamap use the @keyref attribute. This avoids duplicate definitions of the keys and ensures that the new subjects are added to the base enumeration.

The effective result is the same as the following subject scheme map:

<subjectScheme>
  <subjectdef keys="os" navtitle="Operating system">
    <subjectdef keys="linux" navtitle="Linux">
      <subjectdef keys="redhat" navtitle="RedHat Linux"/>
      <subjectdef keys="suse" navtitle="SuSE Linux"/>
    </subjectdef>
    <subjectdef keys="macos" navtitle="Macintosh"/>
    <subjectdef keys="windows" navtitle="Windows">
      <subjectdef keys="winxp" navtitle="Windows XP"/>
      <subjectdef keys="winvis" navtitle="Windows Vista"/>
    </subjectdef>
    <subjectdef keys="zos" navtitle="z/OS"/>
  </subjectdef>
  <enumerationdef>
    <attributedef name="platform"/>
    <subjectdef keyref="os"/>
  </enumerationdef>
</subjectScheme>