Dear All, Although not strictly relevant to the discussion here, I recall once looking at some of the theory of the `region connection calculus' and the work of the Qualitative Spatial and Spatio-temporal Reasoning group at Leeds. This is concerned with the interrelationships between regions of a space. The logical models vary from biHeyting algebras to various multimodal logics. There was some discussion about trying to detect dimension within such RCC systems. If one assumes that `region' is a more basic notion of position than `point' a lot of Euclid still goes through but dimension seems very hard to handle. (I recall that Tarski worked on this area at one time.) Can any one tell me more as it seems of use in Geographic Information Systems= , and other models of qualitative or descriptive spatial information. I know of John Stell's work on this and he has clarified things from a somewhat categorical viewpoint. Perhaps the old puns about `pointless' arguments need revisiting! Tim --=20 Gall y neges e-bost hon, ac unrhyw atodiadau a anfonwyd gyda hi, gynnwys deunydd cyfrinachol ac wedi eu bwriadu i'w defnyddio'n unig gan y sawl y cawsant eu cyfeirio ato (atynt). Os ydych wedi derbyn y neges e-bost hon trwy gamgymeriad, rhowch wybod i'r anfonwr ar unwaith a dil=EBwch y neges. Os na fwriadwyd anfon y neges atoch chi, rhaid i chi beidio =E2 defnyddio, cadw neu ddatgelu unrhyw wybodaeth a gynhwysir ynddi. Mae unrhyw farn neu safbwynt yn eiddo i'r sawl a'i hanfonodd yn unig ac nid yw o anghenraid yn cynrychioli barn Prifysgol Bangor. Nid yw Prifysgol Bangor yn gwarantu bod y neges e-bost hon neu unrhyw atodiadau yn rhydd rhag firysau neu 100% yn ddiogel. Oni bai fod hyn wedi ei ddatgan yn uniongyrchol yn nhestun yr e-bost, nid bwriad y neges e-bost hon yw ffurfio contract rhwymol - mae rhestr o lofnodwyr awdurdodedig ar gael o Swyddfa Cyllid Prifysgol Bangor. www.bangor.ac.uk (YCYG) This email and any attachments may contain confidential material and is solely for the use of the intended recipient(s). If you have received this email in error, please notify the sender immediately and delete this email. If you are not the intended recipient(s), you must not use, retain or disclose any information contained in this email. Any views or opinions are solely those of the sender and do not necessarily represent those of Bangor University. Bangor University does not guarantee that this email or any attachments are free from viruses or 100% secure. Unless expressly stated in the body of the text of the email, this email is not intended to form a binding contract - a list of authorised signatories is available from the Bangor University Finance Office. www.bangor.ac.uk (SEECS)