Definition talk:Monotone Class

There are various compound objects out there consisting of various systems of sets, with various degrees of closure: closed under finite intersections, countable intersections, uncountable intersections, etc., and the same for unions. For example, sigma-algebras, topologies, measure spaces. (This definition is another.)

Wonder whether it's worth putting a page together summarising these by transcluding the relevant bits and indicating a hierarchy: such-and-such is contained in so-and-so, etc. (e.g. "a finite topology is a monotone class" and so on).

See Sequence of Implications of Separation Axioms, for example.

It would be an interesting project, and I've never seen such a thing attempted. But it stands to reason that someone out there has at least thought about it. --prime mover 14:57, 24 March 2012 (EDT)


 * I think this is a good idea; it will allow for a bunch of proofs to be bundled together like is eg. done for general relations, homomorphisms and so on. This will improve the structure and coherence of PW, which is a good thing. So, when do I have time? Wait, there's so much still waiting... --Lord_Farin 17:53, 24 March 2012 (EDT)


 * Time is an illusion caused by lack of acid. I thought everyone knew that. --prime mover 19:21, 24 March 2012 (EDT)

"On $X$" feels best intuitively so I've changed it thus. Plenty of links on the net but I haven't found one that uses any preposition in relation to $X$. I feel it's up to us to innovate. --prime mover 04:19, 25 March 2012 (EDT)