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

[Adam Roach <[e-mail]>]

On 11/15/12 11:58, Flemming Andreasen wrote:
>
> On 11/15/12 11:37 AM, Adam Roach wrote:
>>
>> 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 ?).
You raise a good point. So, yeah, it looks like we probably want to take 
on an existing ABNF (with all its warts and optional things) or define 
our own (which would be trivial -- a plus sign followed by one or more 
digits is some of the most straightforward ABNF you'll ever see written).

/a