20 Sep
2008
20 Sep
'08
4:59 a.m.
In my last post I said that sketches give rise to forgetful functors into Set, which is obviously wrong -- the forgetful functor arising from a given sketch is into the functor category [A,Set], where A is the underlying category of the sketch, and this forgetful functor doesn't determine the sketch up to isomorphism. Mark