Re: [Evolution] vfolders vs filters

[Michael Poole <poole troilus org>]

Ryan Heise <ryan whitewolf com au> writes:

> NotZed wrote:
>
> > Filtering can do other things that vfoldering can't, and vfoldering
> > can cover multiple folders and sources whereas filtering is just incoming
> > mail.
>
> I don't see the point of having real folders any more once you have
> vfolders. Sure, the current vfolder implementation doesn't allow you to
> do some things that folders/filters can do, but you should be able to
> get the same effect with vfolders by being able to assign arbitrary
> attributes to emails, something I've talked about on this list before.
> Suppose you have a filter that puts certain emails in a folder called
> "evolution-list". You could achieve the same thing with vfolders by
> defining a filter that assigns a "evolution-list" attribute to those
> emails instead of "physically" moving those emails into a folder.
[snip]

Those two operations (adding an in-line attribute and filing into a
separate storage) are equivalent, although as you point out if you can
set multiple flags or attributes it becomes more flexible.  The
difference between filtering and vfoldering is (in my mind) one-time
processing -- usually on receipt or retrieval -- and retrieval based
on certain criteria.  If those criteria are expensive to compute, then
it's more efficient to use a static assignment.

One interesting example I have seen for this would be proper handling
of sieve filters (see http://www.imc.org/draft-showalter-sieve-main).
Even if you omit the reject, redirect and discard modes because
Evolution is an MUA rather than an MTA, you still have a potentially
large decision graph (not quite a tree, because several rules in a
sieve script can send mail to the same target, but it's close) for
each folder.  In the general case, it will be costly to perform that
search in real time.

(What's the point of all this?  I'm just expounding on one reason that
people might want to do persistent tagging or one-time filtering of
mail, rather than try to do all their searches in real time.)

-- Michael