How do tag sets work? I created one tag set containing "java" and "caching" and was expecting to get only question related to both of them. But it seems to return question related to any of them which is really useless given the number of matches. Is it possible to get the intersection somehow?
Short answer: tag sets do not currently support intersects (i.e. "java AND caching"), so vote this question up if you want that feature
Tag sets are the union, not the intersect, of the tags you specify. This is consistent with "interesting" and "ignored" tags on the Q&A sites themselves. The idea is that you have a list of tags that you're interested in and want to follow.
I can see a use case for specifying intersects, but it would make the queries more expensive, and the UI more complicated (so I can enter
(java AND caching) OR c# OR asp.net). If enough people want it, we'll figure out how to add it.