Well, I'm working from the premise of a gaming wiki, so I'll
elaborate with that in mind.
I have a portal page for a game system, which is intended to be
the gateway for all material that uses that system. I want to create a
collection of links to the content on my wiki, broken down by category, but I
no longer use categories like "<game system> characters" or
"<game system> campaigns," which have been made obsolete by SMW
and SD. I now use the semantic tag "uses game system::" in each
article, and the articles are categorized into a much simpler tree
(Category:Characters, Category:Campaigns, etc.). On
Special:BrowseData (hereinafter, "S:BD"), these categories are
filtered by, among other things, game system.
Now, this led to my other request about direct links to S:BD
with filters already selected. I want to link to lists of articles that
all have "uses game system::" set to the system on my portal
page. I didn't want to create the external-style links (though I may yet
switch to that), so for the present I'm using #ask: queries to search for
articles that have the right property value.
But it occurred to me that it would be really nice to be able to
further filter the results. If I search for a list of characters under
the game system, perhaps I'd like to filter the results by which campaign they
appear in, for instance, or where they reside. I can arrange the search
results into a table to show that information, I know, but that's not a real
filter. It is also inconsistent with S:BD being the primary article
browser around which my wiki is organized. I'd like to keep a consistent
interface for my users as much as possible. They're not very wiki-savvy
in the first place, and keeping things as simple as possible would be better.
Anyway, direct links to S:BD with filters already selected would
probably take care of me in almost every case. Now that I dwell on it,
the only situation I can think of where a Drilldown Search would be really
handy is if I searched for articles that fell into more than one top-level
category. For instance, if I search for every article that has
"uses game system::" set to the right value, I'll hit articles in
about seven top-level categories. Then I could browse among only those
articles on S:BD, even switching between top-level categories, without seeing
content for other systems or no system at all.
For what it's worth. It would probably require more work
than it would return in functionality. :p