2.1.4.3.8.1 DTD syntax specialization module coding requirements

To be extensible and backward compatible, DITA requires that a DTD implementation of structural and domain specialization modules conform to well-defined implementation (coding) requirements.

These coding requirements implement the specialization architecture with the capabilities and within the limitations of the DTD grammar. They are the coding requirements for structural specializations, element domain specializations, and attribute domain specializations.