FYI - the following is a draft for a new SIEVE operation for testing the
content of MIME part headers. Comments welcome...
First let me say that I think the scope of this extension is right
on target - a simple mechanism that allows searching through embedded
part and message headers and which provides for simple checks against
media type and content disposition parammters is something we need.
Having said that, I think the specifics of how this was done aren't right.
First, as presently written this specification only extends the header test,
and it does so by creating an entirely new test. But there are two other tests
that are equally applicable to inner headers: exists and address. Either
similar "mimeexists" and "mimeaddress" tests need to be added (and perhaps
"mime" changed to "mimeheader"), or this needs to be done within the existing
tests by adding a :mime parameter. I'm indifferent as to which one of these
approaches is chosen, but we do need one of them.
Second, I really don't like the use of an optional middle parameter to specify
that the test is to be performed on a parameter value. This sort of thing is
why we have labelled parameters: It should be done as :parameter or something
similar. As for the use of a null parameter-names value to indicate a test of
non-paramer material, this can done with :parameter as well, but I do worry
that this is a bit tricky. OTOH, I haven't been able to come up with a
differenent way to do it that I like better.
Third, some references probably needs to be made to RFC 2231 and how to handle
encoded parameters. I think the right answer here is to handle this the same
way we already require that encoded words be handled.
A final implementation note. I threw together an implementation of this the
other day and I've already found it to be very useful. IMO this is an
extension we should try and advance sooner rather than later.
Ned