Re: [MMUSIC] [mmusic] #20 (rfc4566bis): 4566bis: Lack of a consistent format for defining new attributes.

[Flemming Andreasen <[e-mail]>]

I think I agree with 4), but the important part here is that we actually 
get a valid ABNF for all extensions.

-- Flemming

On 7/9/14, 8:57 AM, mmusic issue tracker wrote:
> #20: 4566bis: Lack of a consistent format for defining new attributes.
>
>   Paul K.: Many people look to 4566 for examples of how to do this, but it
>   provides bad examples. IMO 4566bis should show the definition of all
>   attributes in a style that complies with a recommended format for defining
>   attributes. (Of course that implies that we could agree on such a format.)
>
>   From http://www.ietf.org/mail-archive/web/mmusic/current/msg13471.html
>
>   One question is whether the definition of a new attribute should:
>   1) define the full syntax of the line (starting with "a="),
>   2) should provide additional definitions of <attribute> (via "/=")
>   3) should provide additional definitions of <att-field> and <att-value>
>     (via "/=")
>   4) provide definitions of the name and value that are consistent with
>     <att-field> and <att-value> without formally extending the
>     definitions of those.
>
>   Note that 4566 loosely follows (4) but gives the definitions informally
>   rather than via ABNF. So it gives no guidance on how to use ABNF for this.
>   A number of drafts have chosen to follow (2). Some have started to do (1)
>   but I don't know of any that ended up that way.
>
>   A question I have raised is: if (2) or (3) is followed, does that mean
>   that the draft doing so must be considered as "updating" 4566?
>
>   One thing that people sometimes forget when defining new attributes is
>   that the syntax of the new attribute MUST also be valid when parsed by the
>   "generic" attribute syntax. AFAIK there is no way in ABNF to specify that.
>   I think that (4) comes closest.
>