Although the conformance clause(s) do a good job distinguishing conformance targets, these have been mentioned many times before the conformance clauses, without much of a definition. For example, "DITA processor" is used abundantly throughout the specification, but I could not find a definition of what it is (even if we can guess intuitively).
A functional definition should be introduced/referred to much earlier - e.g. terminology or glossary - before the conformance clause(s).
Similarly, the term "implementation" is used throughout, but not clearly functionally defined. Only in the conformance clauses we find a tentative definition, which is a bit hard to distinguish from "processor". Couldn't the notion of processor cover such "implementations"? Normally, "implementation" is a generic term that covers all kinds of ways to implement a specification - here to implement DITA including DITA documents.