ietf-mta-filters
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Re: Extension mechanism/support

1998-01-20 12:47:20
Matthew Wall <wall(_at_)cyrusoft(_dot_)com> writes:


However, I think it's arguable that the second proposed requirement, that
it
parse past unknown extensions, really has to apply. In the above instance,
I
want the whole chain to fail so I don't accidentally file away by the wrong
set of colors or something.

This appears to me, on its face, to be the simpler approach and is more
likely to be safe in the sense that fewer unintended consequences are
likely
to happen if the failure mode -- especially on extensions -- is simple. The
authoring filter agent ought simply to be told 'hey, you're yucking around
with some unknown extensions, go fix this' when a commit is attempted.

I guess the scenario that I'm thinking of is where a user has
same filter script both at home and at work.  But at work, he wants
to use the 'black-magic' extension, to deal with certain
intra-company mail.  So he puts in his script:

if (support "black_magic") then {
   black_magic;
}

Now, maybe 'support' isn't the right test to be using here, maybe I
want a 'location' test or some-such;  but the fact remains that unless
we adopt an extension syntax, there's no way the home mail server (assuming
it doesn't support the 'black-magic' extension) can run this script.

(And if we keep the language simple (no loops, substitutions, etc), then
it remains easy to verify that all unknown extensions are properly guarded
by
'if support' clauses before script execution begins.)

Stan