[FOM] "Hidden" contradictions

[Timothy Y. Chow]

Carl Hewitt wrote:

> Inconsistencies are pervasive in large software systems. Unfortunately, 
> these inconsistencies cause "bridges to fall down" with alarming 
> regularity.  In some cases, it has been impossible to trace back which 
> inconsistencies caused a disaster.  See the ACM Risks Forum newsgroup 
> moderated by Peter Neumann for an ongoing saga. Some contradictions have 
> been discovered using subtle reasoning.

Could you be more specific?  I skimmed the file

http://www.csl.sri.com/users/risko/risks.txt

but was not able to identify which "ongoing saga" in particular you were 
referring to.

Also, what exactly do you mean by an "inconsistency" in a large software 
system?  I'm assuming you're not using the word "inconsistency" 
interchangeably with the word "bug."  I'm guessing that you're using 
"inconsistency" to refer to formal software *specifications* rather than 
to software itself?

Tim