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From: G. B. <nonlegitur@nmhp.invalid>
Newsgroups: comp.lang.ada
Subject: Re: Ada in command / control systems
Date: Wed, 6 Mar 2019 07:26:07 -0000 (UTC)
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Xref: reader01.eternal-september.org comp.lang.ada:55794
Date: 2019-03-06T07:26:07+00:00
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Niklas Holsti <niklas.holsti@tidorum.invalid> wrote:

> The design pictures that are really useful for understanding a piece of 
> SW are almost always abstractions and simplifications and could be 
> called "useful lies". Unfortunately this means that the pictures must be 
> manually created, and manually maintained as the SW evolves.

I like to think that there are “almost-pictures”. When I want to understand
a concurrent Ada program, then this may require knowing the communications
while keeping in mind the shared resources. For understanding
communications, Ada offers some visual(!) clues: e.g., the control
structure of a task body together with „accept“ and “requeue”. There may be
“select” at the other end. These appear(!) in predictable places, shaped by
syntax and style(!). That’s the start of a picture . And it’s abstraction,
since presumably I shouldn’t need to study most of the details in between
the visual clues. Call the result semantic folding that focuses on
communications.

I think that pictures can outline these kinds of structure. They document
the participating objects and their interactions. So, maybe the UML, say,
can serve a purpose here, if we manage to link broad ideas (pictures) and
detailed implementation (source) mechanically.