I have posted here: http://www.abstractmath.org/Word%20Press/?p=3739 an explanation of forms, which I first described in 1990. It contains references to most other papers on the subject. Forms are a generalization of sketches. Charles Wells -- professional website: http://www.cwru.edu/artsci/math/wells/home.html gyre&gimble (math blog): http://www.abstractmath.org/Word%20Press/ abstract math website: http://www.abstractmath.org/MM//MMIntro.htm astounding math stories: http://www.abstractmath.org/MM//MMAstoundingMath.htm personal website: http://www.abstractmath.org/Personal/index.html sixwingedseraph.facebook.com [For admin and other information see: http://www.mta.ca/~cat-dist/ ]