hihi, all - yesterday, i read ``four colors suffice'' by robin wilson, which i found to be a very interesting discussion of the four color theorem, and an entertaining and informative account of the history of its proof, but i also noticed a comment about the poincare conjecture that i'd like to know more about, since it has been so often mentioned here of late Wilson writes (at the bottom of p. 178 of my hardbound edition) about Wolfgang Haken separating and reducing the poincare problem into 200 cases and then successfully addressing 198 of them, but not being able to eliminate the last two cases i'd like to know more about what kinds of features this separation into cases might depend on, whether or not anyone else has taken up this kind of approach, with what (partial) success, and whether it's something like taking out all the trivial and easy cases, so that only the really hard ones remain (as happened frequently for the four color theorem) thanx in advance it has always been interesting to me how hard it is to do any kind of useful geometric reasoning in a computer program (much of what i do is pattern recognition systems), and i've wondered for some time how a computing system might be designed to allow planar or 3d geometric reasoning to be more naturally programmed more soon, cal Chris Landauer Aerospace Integration Science Center The Aerospace Corporation cal@aero.org