On Tue, Jan 16, 2007 at 04:09:32PM +0000, Julian Mehnle wrote:
Because the ABNF only describes the formal grammar, while the rest
describes the semantics. That doesn't mean that the grammar should
deliberately allow nonsensical constructs such as "ip4:4444.0.0.0" or
an empty "exp=", though.
Which implicitly expresses your opinion about an empty explanation domain.
Which poses the question: why was it included in the spec as-is, what made
all people involved do the wrong thing?
I mean: It isn't just a typo in the semantics. The specification explicitly
allows an empty domain, except for a small mistake in the BNF. You saying
"nonsensical" isn't enough to undo all the work in the past few years.
On the syntax vs. semantics issue at hand: I think it is perfectly OK
for a syntax to allow ip4:<num>.<num>.<num>.<num> as long as the semantics
make it clear IP addresses do not have numbers above 255. Not every aspect
can be expressed in BNF (at least: not without too much effort resulting in
a way too lenghty specification). If this would be the goal of an RFC, we
would be posting reference implementations, not BNF.
Alex
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