Categorists, Everyone (as far as I know) believes that appropriately defined string diagrams can be used to construct the free compact closed category on a monoidal signature. Kelly-Laplaza proved this only for the case of boxes that have a single wire in and out (i.e. free CCC's on a category, not on an arbitrary moniodal signature). However, at least at the time of publishing his survey (2009), Selinger writes that a general proof doesn't exist in the literature. So, my question is: Is this still the case, and why? Is it simple a question of someone putting in the hours to write this up, or are there serious technical obstacles to the general result? Thanks! Aleks Kissinger [For admin and other information see: http://www.mta.ca/~cat-dist/ ]