This section explains how to implement DTD based document-type shells, specializations,
18.104.22.168 DTD: Overview of coding requirements
DITA coding practices for DTDs rely heavily on entities to implement specialization and constrraints. As such, an understanding of entities is critical when working with DTD document-type shells, vocabulary modules, or constraint modules.
22.214.171.124 DTD: Coding requirements for attribute domain modules
The vocabulary modules that define attribute domains have additional coding requirements. The module must include a parameter entity for the new attribute, which can be referenced in document-type shells, as well as a text entity that specifies the contribution to the @domains attribute for the attribute domain.