Augmented BNF for Syntax Specifications: ABNF
draft-crocker-rfc4234bis-01

With this document, the author is unwilling to make any changes without
restarting the approval process (it's a matter of principal for the
author, and thus not something I want to argue about even if I might
disagree about this application of the principle).  However, a last call
comment on the LWSP issue was not addressed and we are concerned about
that issue.  As this is an otherwise mature specification with
significant community benefit from prompt publication, I suggest this
is a perfect case for an IESG Note.  Here's proposed text:

IESG Note

The IESG has observed widespread use of ABNF in many RFCs with
a significant level of implementation, successful operational
experience and a high degree of technical maturity suitable for a
Internet Standard.  However, one inconsistency was noticed late enough
in the standards process that the community is best served by noting
the issue here without delaying this specification.  The LWSP rule in
appendix B.1 is not compatible with the FWS rule in RFC 2822 and there
have been at least two instances where LWSP was mistakenly used when
FWS was intended.  The IESG cautions ABNF authors to avoid use
of LWSP in email headers and carefully consider whether it is
appropriate to permit whitespace-only folded lines in other contexts
prior to use of that rule.

I think this needs an interoperability report to progress - I have provided one below. As grouping is a functor not operator, I dont' see the unresolved but as being meaningful.  To put it another way, I don't see how to construct a grammar that wold be interpreted differently based on the fix in the reported precedence bug. 


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Interoperability report for 4234  

Several independent implementation of SIP have used the ABNF in 3261 and successfully implement the same grammar as evidenced by the ability to generate and parse messages from other implementations. The following interoperability is based on the open source sip stack at resiprocate.org and Cisco IOS GWs running SIP. 

The ABNF in 3261 uses 

terminal values

strings

ranges

comments

alternates 

sequence groups 

variable repetition

optional sequences

specific repetitions

concatenation 

ABNF is in widespread use in many specification that are used in the internet and seem to produce implementations that interoperate. I believe the degree of technical maturity is evidenced by the number of RFC that use this.