Architectural attributes

DITA provides some attributes to provide type information to processors instead of qualifications or properties of content.

Ordinarily, architectural attributes don't appear in the source files for document instances. Instead, architectural attributes appear in document instances through defaults set in the DTD or Schema declaration. This practice ensures that the creation of document instances cannot produce invalid values for the architectural attributes. These attributes are as follows:

class: This attribute identifies the specialization module for the element type as well as the ancestor element types and the specialization modules to which they belong. Every DITA element has a class attribute.
domains: This attribute identifies the domain specialization modules used in a topic and, for each domains module, its module dependencies. Every topic and map element has a domains attribute.
DITAArchVersion: This attribute identifies the version of the DITA architecture used by the DTD or schema.Every topic and map element has a DITAArchVersion attribute. The attribute is declared in a DITA namespace to allow namespace-sensitive tools to detect DITA markup.

To make the document instance usable without the DTD or Schema declaration, a normalization process can instill the architectural attributes in the document instance.