Terminology

DITA can be understood at the level of an abstract model without reference to particular DTDs, schemas, or actual XML documents. When discussing DITA concepts at this level, the following terminology is used.

Element type

Defines the structure and semantics for a fragment of content.

Specialized element type

Defines an element type as a semantic refinement of another element type. The content allowed by the specialized element type must be a subset of or identical to the content allowed by the original element type.

Topic type

An element type that defines a complete unit of content. The topic type provides the root element for the topic and, through contained element types, substructure for the topic instances. The root element of the topic type is not necessarily the same as the root element of a document type: document types may nest multiple topic types, and may also declare non-DITA wrapper elements as the root element for compatibility with other processes.

Map type

An element type that defines a set of relationships for topic instances. The map type provides the root element and, through contained element types, substructure for the map instances. The map substructure provides hierarchy, group, and matrix organization of references to topic instances.

Structural type

A topic type or map type.

Domain

A set of elements that support a specific subject area. Elements in a domain can be integrated with topic or map types to enhance their semantic support for particular kinds of content. For example, the structural type <topic> declares the <keyword> element; when integrated with a domain for describing user interfaces, new keyword specializations (such as <wintitle>) become available wherever <keyword> was allowed in the original structural type.

Document type

The full set of element types defined in the modules that are integrated by the document type shell. A DITA document type may support authoring multiple topic types or multiple map types, but not a mix of the two. The structural types can be augmented with elements from domains. The term "document type" is used for compatibility with existing standards, since this is the point at which DITA's set of topic, domain, and map types are assembled into a document type that is functionally equivalent to a traditional non-modularized document type.

When the model is expressed in a DTD or schema, the various element types are declared. When referring to these declarations, the following terminology is used.

Element declaration

The representation within a schema technology (such as DTD, XML Schema, or Relax NG) for an element type.

Type module

The representation within a schema technology for the element types uniquely defined by a topic type, map type, or domain.

Topic module

The representation within a schema technology for the element types uniquely defined by a topic type.

Map module

The representation within a schema technology for the element types uniquely defined by a map type.

Structural module

A topic or map module.

Domain module

The representation within a schema technology for the element types uniquely defined by a domain.

Document type shell

The representation within a schema technology for a shell that declares no element types itself but points to and assembles topic, map, and domain modules.

Document type declaration

The representation within a schema technology for a document type. The document type declaration includes the declaration modules assembled by the document declaration shell.

When actual documents, topics, and elements are created based on a DITA document type, the following terminology is used.

Element instance

An occurrence of an element type in a document.

Topic instance

An occurrence of a topic type in a document.

Map instance

An occurrence of a map type in a document.

Structural type instance

An occurrence of a topic type or a map type in a document.

Document instance

A document whose meaning and validity are determined by a document type declaration.