Model

The DITA model has characteristics that are more specific than general XML capabilities.

The DITA model has the following constructs.

Type

Formalizes the meaning and structure for a fragment of information. A type may have:

• A base type.
• Zero or more properties.
• Content consisting of a sequence of positions where each position consists of a type or set and has an occurrence or of text with or without a set.

Set

Identifies commonality across two or more types. The commonality may consist of properties common to the member types or of provision of a kind of content in a position. For convenience, the members of a set can be identified with member sets as well as member types.

Property

Identifies a characteristic of a type. A property may have:

• A base property
• A datatype such as an identifier, a name, a namelist, text, or a list of values.
• A default value.

A property is defined for a type or set of types.

Module

Packages types, sets, and properties. A module can designate some of its specialized types as extensions for their base types.

Shell

Assembles a structural map or topic with domain modules that provide extensions. A shell can potentially constrain topic nesting.

Note: The enumeration of the model above deliberately avoids the standard terminology of XML syntax to decouple the model as much as possible from syntax.