AD is a medium-scale, high-level programming language. Syntactically, it is a sublanguage of ADA.

The specified action semantics for AD constructs does not always correspond exactly to the semantics described in the ADA Reference Manual. For instance, parameter passing modes are left implementation-dependent in ADA, but not in AD.

The action semantic description of AD given here collects and extends the fragmented illustrations given throughout Part III. It also provides the full algebraic specifications of all the semantic entities used in Part III.

Some of the actions specified in Part III are respecified here with some extra subactions. For example, the action representing the execution of a block statement now synchronizes with locally-declared tasks before starting to execute the block body, and relinquishes locally-declared variables afterwards.

The description of AD allows assessment of the pragmatic qualities of action semantics: readability, comprehensibility, modularity, modifiability, etc.

To extend the description of AD to an accurate description of ADA would be a major project, the feasibility of which remains to be seen.

The modular structure of the description is specified first, in the order in which the modules are presented, which is mostly bottom-up.