Re: Writing better software was: Design by Contract (was Re: Interesting thread in comp.lang.eiffel)

["Ken Garlington" <Ken.Garlington@computer.org>]

"Kent Paul Dolan" <xanthian@well.com> wrote in message
news:tavg5.2713$ED.161171@news.wenet.net...
> For those interested in how to write better software, the language is
> not the issue.

Certainly, language is not the *only* issue, but it can have an effect on
your defect rates.

> Arguably the best software ever written was in some
> language "HAL" of which I never heard until reading the case study in
> CMU SEI's "The Capability Maturity Model".

Wasn't HAL invented by Intermetrics for the space program?

> The case study in the above book of necessity only follows the project
> studied up to the book's publication date.  Later breaking news is the
> delivery of a suite of software for space shuttle control with one bug
> detected ever in the delivered product.  Not "one bug per KLOC",
> _one_bug_.

Actually, that's typical for safety-critical software -- for example, I
don't think we've ever received a single defect report from the field for
the production F-16 or F-111 digital flight controls.

> They got to that point with management science, not computer science.

Actually, we (Lockheed Martin Aero) did a benchmarking visit with the space
shuttle control team last year. They will be the first to tell you that it's
both "management science" and "computer science" (not that those are
entirely disjoint terms).

However, they will also tell you that their dollars invested per SLOC is
much higher than the industry average (again, typical for safety-critical
software). It may be that using more "computer science" (e.g., using more
COTS) will permit lower costs while still retaining the kinds of defect
rates expected for this type of software.