John Cartmell (who introduced contextual categories and generalized algebraic theories as models of dependent types in his 1978 Oxford D.Phil thesis and a 1986 Ann. Pure App. Logic paper) worked on topics related to this thread some years ago. Another 1986 paper, 'Formalizing the Network and Hierarchical Data Models --- an Application of Categorical Logic', CATEGORY THEORY AND COMPUTER PROGRAMMING LNCS, 1986, Volume 240/1986, 466-492, DOI: 10.1007/3-540-17162-2_138, can be found via the following link: http://www.springerlink.com/content/y31234tkk63wp56k/ 'Abstract. We have noted that data modelling and conceptual modelling have content and performance as their concerns. For the different data models, the Network and the Hierarchic, we have given logics involving the operations which are physically supported according to the data model. The logics are sensitive to performance in a way that classical logic is not. We have now suggested how we might formalise this. Network and Hierarchical databases have the functional inverse or family as their primitive of organisation. To formalise the Network model we have given a general definition of network category which seems to generalise correctly the hierarchical logic of contextual categories.' There is also relevant work on categories and logic programming. David Pym -- Professor David J. Pym, MA, PhD, ScD, FBCS, CITP, FIMA, CMath, CSci 6th Century Chair in Logic University of Aberdeen Scotland +44 (0)1 224 27 4577 d.j.pym@abdn.ac.uk http://www.abdn.ac.uk/~csc335 The University of Aberdeen is a charity registered in Scotland, No SC013683. [For admin and other information see: http://www.mta.ca/~cat-dist/ ]