Architectural specification : Architectural Specification: Base : Configuration, specialization, and constraints
   
Configuration, specialization, and constraints
 
Overview of DITA extension facilities
Configuration (Document type shells)
Specialization
Constraints
The extension facilities of DITA allow existing vocabulary and constraint modules to be combined to create specific DITA document types. Additionally, vocabulary modules can be extended to create more-specialized markup to meet new requirements not satisfied by existing markup.