A recent question - Page ranking function made me think whether we have an appropriate tag for such question. (And whether we need one).

In my (non-expert) opinion, this falls into information retrieval. (Perhaps it is rather broad category, but we do not want the tags to be too specific.)

We already had a few questions about Page Rank algorithms.

Another example from this area: Probabilistic performance guarantees on information retrieval queries

Unless we have a good tag for this, some appropriate tags for questions of this type might be computer-science and algorithms.

It seems that cstheory and scicomp don't have specific tags for this.

And, of course, if the question is basically asking about some specific mathematical aspect of some king of pageranking algorithm, we can use linear-algebra, matrices or whatever describes well the mathematical question hidden in the background.