Levels of abstraction as maps

So back in May I had a post on levels of abstraction in code, followed this month by some thoughts on finding mappings - these are actually the same thought.

In my invoice example, I imagine a very high-level abstract specification of a specific invoice, then a medium-level specification of the invoice as a generic document, then perhaps a lower-level specification of that document as a PDF. Followed, I guess, by the actual PDF. The point is that each of those specifications represents the same thing.

When I talk about levels of abstraction in a program, this is the same thing again - a high-level summary (or specification) of the parts of the program, and a lower-level specification of the actual program.

I just need to figure out how to express this understandably, and I'm good to go.