[sipcore] draft-barnes-sipcore-rfc4244bis

"Dale Worley" <dworley@nortel.com> Thu, 02 July 2009 18:17 UTC

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From: "Dale Worley" <dworley@nortel.com>
To: SIPCORE <sipcore@ietf.org>
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Date: Thu, 02 Jul 2009 13:49:41 -0400
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Subject: [sipcore] draft-barnes-sipcore-rfc4244bis
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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