Re: [sipcore] draft-barnes-sipcore-rfc4244bis

Dale, Paul,

Good catch.

The intent was not to impose an ordering requirement: the intent was
to impose that the hi-index parameter be present.

Paul: in RFC4244 there was NO ordering requirement.

What we are trying to achieve with the ABNF is:

- No ordering requirement
- There MUST be exactly ONE hi-index
- There MUST be 0 or 1 hi-target parameter
- There MUST be 0 or 1 hi-aor parameter
- There MAY be any number of hi-extension

I now see the current ABNF fails miserably to do this...
But I don't think it's trivial to express in ABNF.

So I think then that Dale's semantic is better, and we
just need to clearly state that index must be present, and
that there can be only 0 or 1 of each of hi-target and hi-aor.

> -----Original Message-----
> From: sipcore-bounces@ietf.org 
> [mailto:sipcore-bounces@ietf.org] On Behalf Of Paul Kyzivat
> Sent: Thursday, July 02, 2009 11:40
> To: Worley, Dale (BL60:9D30)
> Cc: SIPCORE
> Subject: Re: [sipcore] draft-barnes-sipcore-rfc4244bis
> 
> Dale,
> 
> I agree with your concern about the BNF. A requirement about 
> the ordering of the params is problematic.
> 
> OTOH, this is a revision to an existing RFC which had that 
> ordering requirement. Its possible that relaxing it might 
> lead to interop problems.
> 
> Perhaps the best one can do is put in a recommendation to 
> make the index first.
> 
> Regarding indicating that the index is required: it can be 
> done in text, but it can also be done in the BNF, as follows:
> 
>     History-Info = "History-Info" HCOLON hi-entry *(COMMA hi-entry)
> 
>     hi-entry = hi-targeted-to-uri hi-param-list
> 
>     hi-targeted-to-uri = name-addr
> 
>     hi-param-list = *(SEMI hi-option) SEMI hi-index *(hi-option)
> 
>     hi-option = hi-target / hi-aor / hi-extension
> 
>     hi-index = "index" EQUAL 1*DIGIT *("." 1*DIGIT)
> 
>     hi-target = "rc" / "cc" / "mp" / "rt"
> 
>     hi-aor = "aor"
> 
>     hi-extension = generic-param
> 
> 
> 	Thanks,
> 	Paul
> 
> 
> Dale Worley wrote:
> > Regarding the BNF for the History-Info header (section 4.1 in the 
> > draft version of -02):
> > 
> > The current BNF requires that the "index" parameter appear 
> immediately 
> > after the URI, whereas other parameters appear after it:
> > 
> >    History-Info = "History-Info" HCOLON hi-entry *(COMMA hi-entry)
> > 
> >    hi-entry = hi-targeted-to-uri SEMI hi-index *(SEMI hi-param)
> > 
> >    hi-targeted-to-uri = name-addr
> > 
> >    hi-index = "index" EQUAL 1*DIGIT *("." 1*DIGIT)
> > 
> >    hi-param = hi-target/hi-aor/hi-extension
> > 
> >    hi-target = "rc" / "cc" / "mp" / "rt"
> > 
> >    hi-aor = "aor"
> > 
> >    hi-extension = generic-param
> > 
> > IMHO, this is not a good way to organize the grammar, as it 
> makes it 
> > difficult to generate hi-entry's with generic code (there 
> needs to be 
> > some way to constrain the "index" parameter to be first), 
> and violates 
> > the general rule that the order of parameters is not significant.
> > 
> > I propose to adjust the BNF to:
> > 
> >    History-Info = "History-Info" HCOLON hi-entry *(COMMA hi-entry)
> > 
> >    hi-entry = hi-targeted-to-uri *(SEMI hi-param)
> > 
> >    hi-targeted-to-uri = name-addr
> > 
> >    hi-param = hi-index / hi-target / hi-aor / hi-extension
> > 
> >    hi-index = "index" EQUAL 1*DIGIT *("." 1*DIGIT)
> > 
> >    hi-target = "rc" / "cc" / "mp" / "rt"
> > 
> >    hi-aor = "aor"
> > 
> >    hi-extension = generic-param
> > 
> > Of course, the "index" parameter is still mandatory per the 
> semantic 
> > constraints listed earlier in section 4.1.
> > 
> > I've also inserted into the hi-index BNF some spaces around the 
> > instances of "/" for better readability.
> > 
> > Dale
> > 
> > 
> > _______________________________________________
> > sipcore mailing list
> > sipcore@ietf.org
> > https://www.ietf.org/mailman/listinfo/sipcore
> > 
> _______________________________________________
> sipcore mailing list
> sipcore@ietf.org
> https://www.ietf.org/mailman/listinfo/sipcore
> 