[Bug 5418] conformance criteria: "valid if" vs "valid if AND ONLY IF"

http://www.w3.org/Bugs/Public/show_bug.cgi?id=5418





------- Comment #4 from james.lynn@hp.com  2008-01-28 14:51 -------
I agree that we should be as precise as possible, but for the benefit of both
the WG and entire public list I want to be sure it is clear that the "if and
only if" is stating much more than the "if" version and we must be certain for
each of the 3 statements (or more should they arise) that the converse is true.
Taking John's example in comment #2 and restating in the positive, the "if"
version states that "A conforming SML model is valid if it satisfies all of the
following conditions:". Changing it to the "if and only if" version implies
that if a model satisfies all of the following conditions, then it is a
conforming SML model. To convince ourselves that this is the case we might ask
"is there any way a model can satisfy all of these conditions and still not be
a conforming model?" If not then we can feel comfortable about using the "if
and only if". We need to be sure we go through this same "validation exercise"
with each statement that we consider changing.

Received on Monday, 28 January 2008 14:52:03 UTC