Re: ABNF sets and sequences

[Philip Guenther <[e-mail]>]

Dave Crocker <[e-mail]> writes:
...
>Let's get specific about how the construct probably should be used:
>
>RFC 1894:
>
>>2.2 Per-Message DSN Fields
>>
>>    Some fields of a DSN apply to all of the delivery attempts described
>>    by that DSN.  These fields may appear at most once in any DSN.  These
>>    fields are used to correlate the DSN with the original message
>>    transaction and to provide additional information which may be useful
>>    to gateways.
>>
>>      per-message-fields =
>
>         SET (
>
>>           [ original-envelope-id-field CRLF ]
>>           reporting-mta-field CRLF
>>           [ dsn-gateway-field CRLF ]
>>           [ received-from-mta-field CRLF ]
>>           [ arrival-date-field CRLF ]
>>           *( extension-field CRLF )
>
>         )
>
>
>and in draft-ietf-drums-msg-fmt-07.txt:
>
>>name-val-list   =       [CFWS] [name-val-pair *(CFWS name-val-pair)]
>
>becomes
>
>>name-val-list   =       [CFWS]  SET [name-val-pair *(CFWS name-val-pair)]


That syntax makes no separation between the 'tag' that cannot be
repeated and what is being repeated.  That is, it would appear to ban
the following:

    To: [e-mail]
    To: [e-mail]

But not this:
    To: [e-mail]
    To: [e-mail]

Or even:
    To: [e-mail]
    To:     [e-mail]


Such an ABNF operator would have to explicitly specify what part of the
repeated content is required to be unique.  The uniqueness constraint
also has be made on the semantic value of the token, no?
    To: [e-mail]
    tO: [e-mail]


How about obsolete syntax:
    To: [e-mail]
    To : [e-mail]


Philip Guenther

----------------------------------------------------------------------
[e-mail]		UNIX Systems and Network Administrator
Gustavus Adolphus College	St. Peter, MN 56082-1498
Source code never lies: it just misleads (Programming by Purloined Letter?)