referencing to normative content/sections should be more precise in conformance clause

The conformance clauses should be more specific in referring to the normative body of the specification, and give section numbers. E.g. conformance to different types of DITA processors should be more specific on where the requirements are stated. An exemple: "DITA-aware processor ... supports all the base vocabulary modules". I see vocabulary modules in various parts of DITA, but what are the "base" ones? A section(s) referencing would help disambiguate.