Evolution of Date's "Abstract Machine" (via CM)

He then distinguishes the model from its "implementation", defining this to be a "physical realisation on a real machine of the abstract machine".

It appears to me that Date's "abstract machine" is referenced at two separate processes within the prefessional environment of database systems, the first being at the commissioning of the implementation (in the design process perhaps), and the second being during the process of change management --- over the years that follow.

In the second process, due to changes in the environment, new functionality is required, new data structures may be needed, new relationships evoked, new rules created, or old rules changed.

Obviously, the "abstract machine" is consulted at these points and stages, and is itself evolved with respect to its previous "implementation". IOW, subsequent design work will always be required due to the standard considerations incumbent with change, and the reference point for this subsequent design, is the original design of the "abstract machine".

Summarising, theory is just as important, and indeed can be just as critical, in change management as it is at initial design, and effectively, the "abstract machine" is not a static thing but is continually evolved through use.

And in this manner may database systems theory be optimally associated with practice. But nowhere can I find Date saying this, and hence these two questions: