Re: [MMUSIC] E.164 and visual separators in draft-ietf-mmusic-sdp-cs

[Flemming Andreasen <[e-mail]>]

On 11/15/12 11:37 AM, Adam Roach wrote:
> On 11/15/12 09:51, Flemming Andreasen wrote:
>> To be clear, the "global-number" production in RFC 3966 allows for a 
>> number of parameters that are not part of the International E.164 
>> format and thus I have two concerns with the current text
>> 1) The visual-separator exclusion although the ABNF allows for it
>> 2) The apparent disconnect between all of these optional extra 
>> parameters and the above text suggesting they are not allowed.
>
> I don't think these really are issues. There are a lot of 
> specifications where the ABNF would allow for certain productions, 
> while the normative specification making use of that ABNF restricts 
> those productions. For example, there is nothing in the ABNF of RFC 
> 3261 that restricts SIP messages from having multiple CSeq header 
> fields, although it doing so certainly isn't allowed.
>

I think there is a big difference between having an ABNF that includes 
terminals and non-terminals in productions that may not be used at all 
as opposed to having an ABNF with certain semantic restrictions on what 
constitutes valid semantic values based on otherwise valid syntax. The 
former is generally well understood and accepted whereas the latter is 
not (and for good reason IMO - what's the point of having an ABNF 
otherwise ?).

-- Flemming

> /a