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

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

"Stefan Skoglund" <stetson@ebox.tninet.se> wrote in message
news:3985D8F7.754A1584@ebox.tninet.se...
> Ken Garlington wrote:
> > 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.
>
> Those are military program with the belonging red-tape.

The same statement can be made for the Boeing 777, as far as I know. More to
the point, we use the same process whether we are required to follow a
specific process by the contract or not.

> Hmm wondering why the Therac-25 debacle wasn't in my real-time
> programming tution.

It wasn't covered in my real-time systems class, either, but it certainly
was included in my Software Engineering I text.

> > 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.
>
> I doubt it considering that it will only cut down on amount on coding.
> You still
> must do proper testing for example.

Actually, many of the techniques used in high-integrity software (formal
inspections, simulation, etc.) are not tied solely to the coding phase. We
are using them well before we actually write any code. Note also that the
testing process can be improved considerably by (a) reducing the number of
errors that enter the test process and (b) optimizing the test process to
require fewer tests (e.g., by automatically generating some tests from the
requirements).