Re: Another important feature of Ada

[Robert Dewar <robert_dewar@my-deja.com>]

In article <u66ljih85.fsf@infomatch.com>,
  Ray Blaak <blaak@infomatch.com> wrote:

> It sounds good on paper, but in my experience almost all
> interfaces need some modification after coding starts and
> people can actually start using it.

That's too pessimistic in the opposite direction. Whether
interfaces can remain stable depends on several things:

  1. The quality and effort of work to design the interfaces
  2. How well defined the project is
  3. How well organized the project is
  4. Cohesiveness of the team doing the work

Certainly I can give a counter example. In the mid 70's I
did a real time operating system, PD/FMS for Incoterm/Honeywell.
Itwas roughly similar to say the VxWorks kernel, with a complete
set of tools (assemblers, linkers, file system including full
indexed files, system utilities, editor, shells etc) to support
program development.

The entire system was approximately half a million lines of
assembly language, including comments, and it was perhaps
half comments.

The way I proceeded was first to write the entire programmers
reference manual for the kernel with full details of all
callings sequences for thread scheduling etc, and the full
users manual for the program development system. These manuals
were edited into something very close to the final form in which
they were delivered to customers, with discussion on details
*before a single line of code was written*, and the only changes
were very minor (mostly style editing) from then to the final
release. The system was quite successful and was used in some
10,000 sites. My favorite note was from one person who some
years later was forced to switch from PD/FMS to Unix, and was
complaining that it seemed a big step backwards :-)

Of course it helps to have a one person project, since it is
easier to keep everything under control and organized, but I
think this same discipline can be applied to many other
projects.

I would agree you can't achieve it with all projects, but it is
a legitimate and reasonably goal, and it is giving up too easily
to decide that it will fail in "almost all" cases.

Robert Dewar


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