Is the use of hierarchic tags too redundant?

Is there a policy which tags to use when there is an obvious hierarchy? For instance, questions with tags or could also be tagged more generally to make searches easier, and indeed they are more or less often. But sometimes this may seem too redundant. Likewise for $\subset$ and obviously lots of other pairs.

How should that be handled best?

1 Answer

Two basic pieces of information:

• One should always use at least one top-level tag (those with 2-letter prefix corresponding to arXiv categories).

• One can use up to five tags; there seems no reason not to make use of all slots if there are enough relevant tags.

I think it is good practice to use both general and specific tags if they apply.
Like use , , to then add and maybe is a bit much (but there'd be no harm either).

A key-point to keep in mind is that one can follow and filter by certain tags. It thus makes sense to include general tags even if everybody seeing the more special tag would know the more general tag for if the general tag is missing they might never see the question.

More information along these lines can be found on the Frequently asked questions about tagging on MathOverflow

• Yes, I think that is the most important argument: "if the general tag is missing, they might never see the question". – Wolfgang Jul 22 '15 at 15:04
• Agreed, usually, two top level tags, and a specific tag belonging to a different general tag, to indicate approach to the problem, if not in those categories. Only then, if any slots remain (often not), fill in a slot with a specific tag belonging to one of the general subjects tagged. Then the question arrives to the right readers. – Gottfried William Jul 23 '15 at 14:21