On Wed, 2004-10-06 at 13:55, william(at)elan.net wrote:
On Wed, 6 Oct 2004, Mark Lentczner wrote:
Repeated Modifiers
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Section 4.6.3 says "The same key MUST NOT appear in more than one
modifier in a record." The intent is that modifiers cannot be
repeated, and any repetition results in a syntax error (PermFail).
Why can they not be repeated?
Modifiers are something that some clients are able to process and some
can not. Its up to the client to be able to decide if repetition of
the modifier is to be considered an error in regards to that modifier
or not. But I don't think this should be disallowed for all modifiers
directly by the protocol draft.
Although I am fine with multiple exp='s in the same record resulting in
an error, with the spec trying to restrict the currently-defined
modifiers in that way:
1. I don't see why the same should be true for unknown modifiers.
There is a conflict between "unknown modifiers are ignored",
and the concept of all repeated modifiers resulting in PermFail.
Although I'm fine with a PermFail result for the currently-defined
modifiers, I don't think this should extend to future modifiers.
If a later experimental draft defined the "foo=" modifier, for use
within v=spf1 records, and with foo= being allowed to appear
multiple times, I wouldn't want older implementations to work when
there was one foo= by merely ignoring it, and fail when there were
two foo='s with PermFail. Instead, I'd want it to ignore all foo='s
in all cases.
2. I'm assuming that if a base record has an "exp=", and an included
record has another "exp=", that this isn't considered a duplicate
modifier. (With the included exp= used if a failure occurred there,
and the outer exp= used if the failure occurred there.)
--
Mark Shewmaker
mark(_at_)primefactor(_dot_)com