I am reading math books and articles (for applications in other disciplines, mostly about logics for computer science and AI) and the hardest part is to memorize formulas, to look up some definitions/facts (when proof in another part of the book requires it or simply states that it is so) or to restate the formulas from one chapter from the book into the notation of another chapter of the book.
To cope with this I usually take a notes and try to introduce some order but from time to time it does not work (not at least of the growing volume of paperwork).
The question is - are there any tools for mathematicians to cope with this - maybe it can be some kind of electronic notebook where the formulas can be entered in for once and where the search can be done effectively, the proofs can be elaborated and so on.
And - another question - are there efforts to create ontology of mathematical definitions, objects and facts? I see that there was some effort in nineties (e.g. http://www-ksl.stanford.edu/knowledge-sharing/papers/engmath.html) but currently google gives lot of results in the the philosophy of mathematics but little practical projects (good exception is article http://www.semantic-web-journal.net/content/ontologies-and-languages-representing-mathematical-knowledge-semantic-web)
I understand - memorizing it the simplest part of the mathematicians work (it just happens when the one search solution to some problems) but it can be a bit hard for some who just tries to apply math.
The following two links are interesting examples of such kind of efforts (although my intention was a bit different): http://www.cs.man.ac.uk/~ezolin/ml/ http://www.cs.man.ac.uk/~ezolin/dl/
I wanted this to be a open service to everyone but now I see - the copyrights can be a great issue. Certainly - if some book or journal article is digested in such format, there should be objections by publishing houses. From the other hand - if author provides openly available preprint of his of her work, then maybe such work can be reformulated in formal/ontology format without objections by publishers or the authors. Clearly, the current state of affairs should be changed in the future, if technology should progress.