n versioning is there any other better approach

n versioning is there any other better approach

[Ananth the Boss]

we are developing safety critical flight software by n version
approach.also we validate performance of flight software by comparing
results of software with that of another version(autonomous).how can
this be effective.ther may b a chance that autonomous may b wrong.since
'n' times the same task of development has 2 b carried out time and
labor involved is wasted in this strategy.

Re: n versioning is there any other better approach

[Larry Kilgallen]

In article <1145599506.289672.274530@u72g2000cwu.googlegroups.com>, "Ananth the Boss" <anboss@gmail.com> writes:

> we are developing safety critical flight software by n version
> approach.also we validate performance of flight software by comparing
> results of software with that of another version(autonomous).how can
> this be effective.ther may b a chance that autonomous may b wrong.since
> 'n' times the same task of development has 2 b carried out time and
> labor involved is wasted in this strategy.

1. I don't think you will have much luck with such inattention to spelling
   and capitalization.  (Ada does not require the latter, but documentation
   does.

2. Formal Proof is a different approach from multiple versions.

3. Multiple versions do not count as multiple versions of they were done
   by the same team.  Probably they should also not be done in the same
   programming language.

Re: n versioning is there any other better approach

[Robert A Duff]

Kilgallen@SpamCop.net (Larry Kilgallen) writes:

> 3. Multiple versions do not count as multiple versions of they were done
>    by the same team.  Probably they should also not be done in the same
>    programming language.

How about, "Multiple versions do not count as multiple versions if they
were done by members of the same species"?  I mean, we're all human, and
many of us have a tendency toward the same sort of errors (off-by-one
errors, inability to find all sources potentially affected by a certain
change, etc).

Multiple versions can certainly help, but it doesn't help nearly as much
as one would like.  It sure would be nice if, given a probability P of
error, N versions would make it P**N.  With software, it's not that
good, because my errors are not independent of your errors, because our
brains think alike to some extent.

By the way, the original poster should look at SPARK.

- Bob

Re: n versioning is there any other better approach

[Jeffrey R. Carter]

Robert A Duff wrote:
> 
> Multiple versions can certainly help, but it doesn't help nearly as much
> as one would like.  It sure would be nice if, given a probability P of
> error, N versions would make it P**N.  With software, it's not that
> good, because my errors are not independent of your errors, because our
> brains think alike to some extent.

I saw a study once that indicated that multiple versions tend to have 
similar errors.

-- 
Jeff Carter
"I'm a kike, a yid, a heebie, a hook nose! I'm Kosher,
Mum! I'm a Red Sea pedestrian, and proud of it!"
Monty Python's Life of Brian
77

Re: n versioning is there any other better approach

[Larry Kilgallen]

In article <25f2g.111486$oL.37868@attbi_s71>, "Jeffrey R. Carter" <spam.not.jrcarter@acm.not.spam.org> writes:
> Robert A Duff wrote:
>> 
>> Multiple versions can certainly help, but it doesn't help nearly as much
>> as one would like.  It sure would be nice if, given a probability P of
>> error, N versions would make it P**N.  With software, it's not that
>> good, because my errors are not independent of your errors, because our
>> brains think alike to some extent.
> 
> I saw a study once that indicated that multiple versions tend to have 
> similar errors.

Do you recall whether there was any commonality in the versions, other
than the specification ?   Like language, background of implementers,
deadline, etc. ?

Re: n versioning is there any other better approach

[Jeffrey R. Carter]

Larry Kilgallen wrote:
> 
> Do you recall whether there was any commonality in the versions, other
> than the specification ?   Like language, background of implementers,
> deadline, etc. ?

Sorry, no, just that the versions were developed independently.

-- 
Jeff Carter
"It's all right, Taggart. Just a man and a horse being hung out there."
Blazing Saddles
34

Re: n versioning is there any other better approach

[Peter Amey]

Jeffrey R. Carter wrote:
> Larry Kilgallen wrote:
> 
>>
>> Do you recall whether there was any commonality in the versions, other
>> than the specification ?   Like language, background of implementers,
>> deadline, etc. ?
> 
> 
> Sorry, no, just that the versions were developed independently.
> 

Are you perhaps thinking of the Knight-Leveson experiment?  The paper is 
  on line somewhere.

ISTR that they got teams of students independently to implement the same 
specification.  The interesting result is that the programs all tended 
to fail the same, hard, test cases - e.g. area of a figure in the case 
where all the vertices were 0,0 or intersection of lines that are 
parallel.  The conclusion was that N version gives some protection from 
random errors but that real errors aren't very random!

Peter

Re: n versioning is there any other better approach

[Ananth the Boss]

can u give me links/references for formal proof approach
thanks

Re: n versioning is there any other better approach

[Ananth the Boss]

hello
SPARK?
can u give some references for SPARK so that i can proceed reading
futher .
thanks

Re: n versioning is there any other better approach

[Ananth the Boss]

thanks all of you for all ur valuable suggestions.

Re: n versioning is there any other better approach

[Simon Clubley]

In article <1145851455.760040.151650@i40g2000cwc.googlegroups.com>, "Ananth the Boss" <anboss@gmail.com> writes:
> can u give me links/references for formal proof approach
> thanks
> 

A link to Praxis:

	http://www.praxis-his.com/sparkada/

Question: Is your safety critical application something that you are
developing as part of a university project (or similar) or will lives
actually depend on the correct functioning of your software ?

Simon.

-- 
Simon Clubley, clubley@remove_me.eisner.decus.org-Earth.UFP
If Google's motto is "do no wrong", then how did we get Google Groups 2 ?