2.5 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.
2.5.1 Overview of DITA extension facilities
DITA provides three extension facilities: configuration, constraint, and specialization. In addition, generalization augments specialization.
Configuration enables the definition of DITA document types that include only the vocabulary modules that are required for a given set of documents. There is no need to modify the vocabulary modules. Configurations are implemented as document-type shells.
The specialization feature of DITA allows for the creation of new element types and attributes that are explicitly and formally derived from existing types. This facilitates interchange of conforming DITA content and ensures a minimum level of common processing for all DITA content. It also allows specialization-aware processors to add specialization-specific processing to existing base processing.
Generalization is the process of reversing a specialization. It converts specialized elements or attributes into the original types from which they were derived.
Constraint modules define additional constraints for vocabulary modules in order to restrict content models or attribute lists for specific element types, remove certain extension elements from an integrated domain module, or replace base element types with domain-provided, extension element types.