From cat-dist Sun Feb 2 14:03:37 1997 Received: by mailserv.mta.ca; id AA00703; Sun, 2 Feb 1997 14:02:41 -0400 Date: Sun, 2 Feb 1997 14:02:41 -0400 (AST) From: categories To: categories Subject: Manuscript Message-Id: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Status: RO X-Status: Date: Sun, 2 Feb 1997 17:11:05 GMT From: MHEBERT@acs.auc.eun.eg Here is an Abstract of a manuscript recently submitted, and available on request. Part of it was presented at the last summer Sussex Category Meeting. On generation and implicit partial operations in locally presentable categories Michel Hebert (The American University in Cairo, Cairo, Egypt) Abstract. In a locally a-presentable category C, seen as a category of a-ary S-sorted structures, we describe the subobjects (resp. the regular, strong subobjects) generated by a subset, first in terms of closure under specific types of implicit partial operations (IPO), and then in syntactic terms, using variations on the concept of dominion. This extends previous results from [Hebert, Can. J.Math 93]. The domain of definition of an IPO of arity s ->s is a subfunctor V >--> U(s) of the appropriate forgetful functor, and each limit-closed domain V determines, in a natural way, a structure P(V) in C having as its elements of sort s the (s->s)-ary IPO's with domain V (This generalizes the fact that the elements of sort s of the free structure F(s) can be seen as the (s->s)-ary implicit total operations in C). The P(V)'s for subobject-closed V >--> Us with | s | < a are precisely the a-generated objects (in the sense of Gabriel-Ulmer) of C. Finally we use IPO's to give a characterization of the so-called a-retractions, which parallels the known syntactic characterization of a-pure morphisms. The point of view adopted in this paper is the one of the algebraist or model-theorist wishing to use the tools of category theory without making radical changes in the concrete description of his/her favourite structures (in particular without modifying the type). A part of the paper deals with the translation problems which arise. From cat-dist Mon Feb 3 15:54:35 1997 Received: by mailserv.mta.ca; id AA10231; Mon, 3 Feb 1997 15:53:09 -0400 Date: Mon, 3 Feb 1997 15:53:09 -0400 (AST) From: categories To: categories Subject: 4th WoLLIC'97 - 2nd Call Message-Id: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Status: O X-Status: Date: Mon, 3 Feb 1997 10:10:57 -0300 From: ruy@di.ufpe.br [Please post. Apologies if you received this message more than once.] Second Call for Contributions 4th Workshop on Logic, Language, Information and Computation (WoLLIC'97) August 20-22, 1997 Fortaleza (Ceara'), Brazil The "4th Workshop on Logic, Language, Information and Computation" (WoLLIC'97) will be held in Fortaleza, Ceara' (Brazil), from August 20th to 22nd 1997. Contributions are invited in the form of two-page (600 words) abstracts in all areas related to logic, language, information and computation, including: pure logical systems, proof theory, model theory, algebraic logic, type theory, category theory, constructive mathematics, lambda and combinatorial calculi, program logic and program semantics, logics and models of concurrency, nonclassical logics, nonmonotonic logic, logic and language, discourse representation, logic and artificial intelligence, automated deduction, foundations of logic programming, logic and computation, and logic engineering. There will be a number of guest speakers, including: Keith Devlin (St.Mary's Coll), Abbas Edalat (Imperial Coll), Rob van Glabbeek (Stanford), Yuri Gurevich (Michigan Univ), Peter Johnstone (Cambridge Univ), Roman Kossak (CUNY), Daniel Lehmann (Jerusalem Univ), Drew McDermott (Yale Univ), Michael Moortgat (Utrecht Univ), Moshe Vardi (Rice Univ), Paulo Veloso (PUC-Rio). Submission: Two-page abstracts, preferably by e-mail to *** wollic97@di.ufpe.br *** must be RECEIVED by JUNE 1st, 1997 by one of the Co-Chairs of the Organising Committee. Authors will be notified of acceptance by July 1st, 1997. The 4th WoLLIC'97 is under the official auspices of the Interest Group in Pure and Applied Logics (IGPL), The European Association for Logic, Language and Information (FoLLI), and co-sponsored by the Association for Symbolic Logic (ASL), and the Sociedade Brasileira de Computacao (SBC). Abstracts will be published in the Journal of the IGPL (ISSN 0945-9103) (Oxford University Press) as part of the meeting report. Selected contributed papers will be invited for submission (in full version) to a special issue of the Journal of the IGPL (http://www.mpi-sb.mpg.de/igpl/Journal). The location: Located near the equatorial line in the northeastern coast of Brazil, Fortaleza, the capital of the state of Ceara', lies by the beach between the Ceara' and the Coco' rivers, in the middle of 570km (360mi) of sandy beaches of the State's coast. The hightest point in the city is only 30m (100ft) high and its beach front is formed of sand dunes up to 10m high and coconut trees. The weather is dry and sunny. A permanent breeze comes from the ocean and keeps the air clean and healthy while the temperature rests on a nice level year around. The lack of rain during most of the year, now a blessing for the visitors, prevented a definitive settlement in the area of Fortaleza until the middle of the 17th century. At that time, need to assure the hold of the land, the Portuguese established the "Fortaleza de Nossa Senhora da Assuncao" in the same place where a hundred years before the dutch had built the Schoonenbroch Fort. Fortaleza, named after the fortress, has been since then an important trading center and an artistic and cultural center of the country. (http://www.bec.hosting.ibm.com/pagina/ifortale.html) (http://www.bec.hosting.ibm.com/pagina/iceara.html) Programme Committee: A. Avron (Tel-Aviv Univ., Israel), J. van Benthem (ILLC, Amsterdam), W. A. Carnielli (UNICAMP, Campinas), N. da Costa (USP, Sao Paulo), I. Hodkinson (Imperial College, London), L. Moss (Indiana Univ., Bloomington), V. de Paiva (Birmingham Univ., UK), T. Pequeno (UFC, Fortaleza), R. de Queiroz (UFPE, Recife), P. Veloso (PUC, Rio). Organising Committee: M. Aragao (UFC), F. Carvalho (UFC), A. T. C. Martins (UFC), H. Nogueira (UFC), A. G. de Oliveira (UFBA/UFPE), M. Pequeno (UFC) (Chair), T. Pequeno (UFC), R. de Queiroz (UFPE), W. Vasconcelos (UECE). For further information, contact the Co-Chairs of the Organising Committee: Ruy de Queiroz, Departamento de Informatica, Univ. Federal de Pernambuco, CP 7851, Recife, PE 50732-970, Brazil, e-mail: ruy@di.ufpe.br, tel.: +55 81 271 8430, fax: +55 81 271 8438. Marcelino Pequeno, Laboratorio de Inteligencia Artificial, Univ. Federal do Ceara', CP 12166, Fortaleza, CE 60455-760, Brazil, e-mail: marcel@lia.ufc.br, tel.: +55 85 287 1333, fax: +55 85 288 9845. Web homepage: http://www.di.ufpe.br/~wollic97 %----- % LaTeX version %----- \documentstyle[a4]{article} \renewcommand{\thepage}{} \begin{document} \begin{center} {\large\bf 4th Workshop on Logic, Language, Information and Computation (WoLLIC'97)}\\[1.0ex] Sponsored by IGPL, FoLLI, ASL, SBC\\[0.8ex] {\large August 20--22, 1997}\\ {(Tutorial Day: August 19th)}\\[.8ex] {\large Fortaleza (Cear\'a), Brazil}\\[1.0ex] \end{center} \medskip \noindent The {\bf 4th Workshop on Logic, Language, Information and Computation} ({\bf WoLLIC'97}) will be held in Fortaleza, Cear\'a (Brazil), from August 20th to 22nd 1997. Contributions are invited in the form of two-page (600 words) abstracts in all areas related to logic, language, information and computation, including: pure logical systems, proof theory, model theory, algebraic logic, type theory, category theory, constructive mathematics, lambda and combinatorial calculi, program logic and program semantics, logics and models of concurrency, nonclassical logics, nonmonotonic logic, logic and language, discourse representation, logic and artificial intelligence, automated deduction, foundations of logic programming, logic and computation, and logic engineering.\\ There will be a number of guest speakers, including: Keith Devlin (St.Mary's Coll), Abbas Edalat (Imperial Coll), Rob van Glabbeek (Stanford Univ), Yuri Gurevich (Michigan Univ), Peter Johnstone (Cambridge Univ), Roman Kossak (CUNY), Daniel Lehmann (Jerusalem Univ), Drew McDermott (Yale Univ), Michael Moortgat (Utrecht Univ), Moshe Vardi (Rice Univ), Paulo Veloso (PUC-Rio)\\ {\bf Submission}: Two-page abstracts, preferably by e-mail to *** wollic97@di.ufpe.br *** must be RECEIVED by JUNE 1st, 1997 by one of the Co-Chairs of the Organising Committee. Authors will be notified of acceptance by July 1st, 1997. The {\em 4th WoLLIC'97\/} is under the official auspices of the {\em Interest Group in Pure and Applied Logics\/} ({\em IGPL\/}), The {\em European Association for Logic, Language and Information\/} ({\em FoLLI\/}), and co-sponsored by the {\em Association for Symbolic Logic\/} ({\em ASL\/}), and the {\em Sociedade Brasileira de Computa\c{c}\~ao\/} ({\em SBC\/}). Abstracts will be published in the {\em Journal of the IGPL\/} (ISSN 0945-9103) (Oxford University Press) as part of the meeting report. Selected contributed papers will be invited for submission (in full version) to a special issue of the {\em Journal of the IGPL\/} (http://www.mpi-sb.mpg.de/igpl/Journal).\\ {\bf The location}: Located near the equatorial line in the northeastern coast of Brazil, Fortaleza, the capital of the state of Cear\'a, lies by the beach between the Cear\'a and the Coc\'o rivers, in the middle of 570km (360mi) of sandy beaches of the State's coast. The hightest point in the city is only 30m (100ft) high and its beach front is formed of sand dunes up to 10m high and coconut trees. The weather is dry and sunny. A permanent breeze comes from the ocean and keeps the air clean and healthy while the temperature rests on a nice level year around. The lack of rain during most of the year, now a blessing for the visitors, prevented a definitive settlement in the area of Fortaleza until the middle of the 17th century. At that time, need to assure the hold of the land, the Portuguese established the `Fortaleza de Nossa Senhora da Assun\c{c}\~ao' in the same place where a hundred years before the dutch had built the Schoonenbroch Fort. Fortaleza, named after the fortress, has been since then an important trading center and an artistic and cultural center of the country. (http://www.bec.hosting.ibm.com/pagina/ifortale.html)\\ {\bf Programme Committee}: A.\ Avron (Tel Aviv Univ., Israel), J.\ van Benthem (ILLC, Amsterdam), W.\ A.\ Carnielli (UNICAMP, Campinas), N.\ da Costa (USP, S\~ao Paulo), I.\ Hodkinson (Imperial College, London), L.\ Moss (Indiana Univ., Bloomington), V.\ de Paiva (Birmingham Univ., UK), T.\ Pequeno (UFC, Fortaleza), R.\ de Queiroz (UFPE, Recife), P.\ Veloso (PUC, Rio).\\ {\bf Organising Committee}: M.\ Arag\~ao (UFC), F.\ Carvalho (UFC), A.T.C.\ Martins (UFC), H.\ Nogueira (UFC), A.G.\ de Oliveira (UFBA/UFPE), M.\ Pequeno (UFC) (Chair), T.\ Pequeno (UFC), R.\ de Queiroz (UFPE), W.\ Vasconcelos (UECE).\\ For further information, contact the Co-Chairs of Organising Committee: R.\ de Queiroz, Departamento de Inform\'atica, Universidade Federal de Pernambuco (UFPE) em Recife, Caixa Postal 7851, Recife, PE 50732-970, Brazil, e-mail: ruy@di.ufpe.br, tel: +55~81~271~8430, fax +55~81~271~8438.\\ M.\ Pequeno, Laborat\'orio de Intelig\^encia Artificial, Univ.\ Federal do Cear\'a, CP 12166, Fortaleza, CE 60455-760, Brazil, e-mail: marcel@lia.ufc.br, tel.: +55~85~287~1333, fax: +55~85~288~9845.\\ Web homepage: http://www.di.ufpe.br/$^\sim$wollic97 \end{document} From cat-dist Tue Feb 4 10:06:05 1997 Received: by mailserv.mta.ca; id AA26693; Tue, 4 Feb 1997 10:05:30 -0400 Date: Tue, 4 Feb 1997 10:05:29 -0400 (AST) From: categories To: categories Subject: CTCS'97 Message-Id: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Status: RO X-Status: Date: Tue, 4 Feb 1997 14:32:31 +0100 From: Eugenio Moggi CATEGORY THEORY AND COMPUTER SCIENCE (CTCS'97) 4-6 SEPTEMBER 1997, S. MARGHERITA LIGURE (GENOA), ITALY URL: "http://www.disi.unige.it/conferences/ctcs97/" SECOND CALL FOR PAPERS The seventh biennial conference on Category Theory and Computer Science is to be held in Santa Margherita Ligure in 1997. Previous meetings have been held in Guildford, Edinburgh, Manchester, Paris, Amsterdam and Cambridge. IMPORTANT DATES: - 01 Mar 1997, deadline for ELECTRONIC SUBMISSIONS - 01 May 1997, notification of acceptance/rejection - 15 Jun 1997, deadline for final version ** ELECTRONIC SUBMISSION GUIDELINES ** - Papers must describe original unpublished research, be written and presented in English, they must not exceed 20 pages nor be submitted for publication elsewhere. - Papers can be submitted via an electronic form or by e-mail (see the conference URL for details). - ALTERNATIVE METHODS OF SUBMISSION might be accepted, but should be agreed with ctcs97@disi.unige.it no later than 15th FEBRUARY 1997. SCOPE. The purpose of the conference series is the advancement of the foundations of computing using the tools of category theory, algebra, geometry and logic. Whilst the emphasis is upon applications of category theory, it is recognized that the area is highly interdisciplinary and the organizing committee welcomes submissions in related areas. Topics central to the conference include: - Models of computation - Program logics and specification - Type theory and its semantics - Domain theory - Linear logic and its applications - Categorical programming Submissions purely on category theory are also acceptable as long as the applicability to computing is evident. It is anticipated that the proceedings will be published in the LNCS series. ORGANIZING AND PROGRAMME COMMITTEE: S. Abramsky (UK) P.-L. Curien (France), P. Dybjer (Sweden), P. Johnstone (UK), G. Longo (France), G. Mints (USA), J. Mitchell (USA), E. Moggi (Italy), A. Pitts (UK), A. Poigne (Germany), G. Rosolini (Italy), D. Rydeheard (UK), F-J. de Vries (Japan). LIST OF INVITED SPEAKERS: J. Baez, Univ. of California at Riverside (USA) R. Bird, Oxford Univ. (UK) B. Jay, Univ. of Technology Sydney (Australia) RELATED EVENTS: workshop Express'97, 8-12 Sep 1997, Santa Margherita Ligure, Italy. -- From cat-dist Tue Feb 4 13:30:13 1997 Received: by mailserv.mta.ca; id AA05946; Tue, 4 Feb 1997 13:29:22 -0400 Date: Tue, 4 Feb 1997 13:29:21 -0400 (AST) From: categories To: categories Subject: question on functors adjoint to their dual Message-Id: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Status: O X-Status: Date: Tue, 4 Feb 1997 16:44:39 GMT From: Hayo Thielecke I am interested in the following situation: a contravariant functor adjoint to its own dual, with the unit and counit being the same morphism, but _not_ an iso. The canonical example is the contravariant internal hom on a cartesian (or just symmetric monoidal) closed category, [(_) -> A] for some object A. My question is: is this typical, or are there (interesting) examples of such adjunctions that do not come from exponentials? Thanks, Hayo Thielecke From cat-dist Tue Feb 4 14:12:51 1997 Received: by mailserv.mta.ca; id AA03255; Tue, 4 Feb 1997 14:12:15 -0400 Date: Tue, 4 Feb 1997 14:12:15 -0400 (AST) From: categories To: categories Subject: PhD student positions Message-Id: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Content-Transfer-Encoding: QUOTED-PRINTABLE Status: RO X-Status: Date: Tue, 04 Feb 1997 19:00:02 +0100 From: Johan Jeuring The Department of Computing Science at the Chalmers University of Technology and G=F6teborgs University announces free PhD positions. The major research topics at the department are programming logic and type theory, functional programming, cognition technology, and algorithms and discrete optimisation, but research is also carried out in a number of other topics. More information about the research at the department can be found on the WWW on page: http://www.cs.chalmers.se/ComputingScience/Research Most PhD positions are five year scholarships. The PhD student will spend about 80 percent of his or her time on graduate studies, and about 20 percent on teaching. Applicants must have an undergraduate degree in Computer Science with excellent results. The department tries to increase the number of female employees, and especially welcomes female applicants. At the moment the scholarships consist of 14500 (19000) SEK per month in the first (last) year. Usually a foreign PhD student does not teach in his or her first year in Sweden, and as a consequence the scholarship is of a slightly smaller size. More information about the graduate programmes can be found on the WWW on page: http://www.cs.chalmers.se/ComputingScience/Graduate To apply, send us a letter in English, covering=20 1 data about yourself; 2 a copy of an official paper giving grades from your undergraduate degree(s);=20 3 a statement about your main interests; 4 some letters of recommendation from people that know you as a student or as an employee; 5 any scientific papers you have written. Send your application to=20 Section for Mathematics and Computer Science Chalmers University of Technology 412 96 G=F6teborg Sweden Furthermore, send an email containing the data about yourself to=20 johanj@cs.chalmers.se The last date for your application to arrive is March 3, 1997. A decision about to whom we will offer the PhD positions will be taken before June 1, 1997. From cat-dist Tue Feb 4 16:30:47 1997 Received: by mailserv.mta.ca; id AA11678; Tue, 4 Feb 1997 16:29:17 -0400 Date: Tue, 4 Feb 1997 16:29:17 -0400 (AST) From: categories To: categories Subject: CT97: Second Announcement Message-Id: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Status: RO X-Status: Date: Tue, 4 Feb 97 12:10:00 -0800 From: John MacDonald Please circulate to all interested colleagues: SECOND ANNOUNCEMENT INTERNATIONAL CATEGORY THEORY MEETING (CT97) July 13-19, 1997 University of British Columbia Vancouver, Canada The conference arrival day is Sunday July 13 with a reception in the evening. The scientific program will begin Monday morning July 14 and will finish before lunch on Saturday July 19. PREREGISTRATION IF YOU HAVE NOT ALREADY DONE SO, AND PLAN TO ATTEND THE CONFERENCE, PLEASE PREREGISTER BY MARCH 15, 1997. To preregister, and thus receive detailed information, please send e-mail to johnm@math.ubc.ca with subject `preregistration'. Please provide your name and a postal address in the body of the message. REGISTRATION FEE The conference registration fee is tentatively set at $225(Canadian) if received before the end of May and $250 if received afterwards. The final figure depends on some cost estimates not yet received but will not vary much (if at all) from this tentative figure. The registration fee includes a reception Sunday evening, morning coffees, a midweek excursion, a banquet Friday evening as well as various fees charged by the University (e.g. meeting room rentals). Tickets to attend any of the events will be available at cost for spouses, children, or other accompanying persons. Final figures as well as method of payment will be sent to those who have preregistered. ACCOMODATION AND MEALS Accomodation is available on the U.B.C. campus in a block of rooms being held for CT97 until one month before the meetings begin. These rooms as well as reasonably priced student eating places and a pub are all located within easy walking distance of the talks. A form for booking rooms on campus will be sent soon to all preregistrants. For your advance information the costs of accomodation are as follows: A single room with shared washroom is $33. per night; A single room with private washroom is $60. per night; A single/double suite (1 double bed) is $95. per night; and A triple suite (2 twin beds, 1 double) is $110. per night. These rates are in Canadian funds and do not include taxes, which will be added to the rates quoted. The accomodation quoted at $60, $95 and $110 includes TV, telephone, kitchenette and private washroom. Breakfast is not included, but is available nearby. Those who prefer to book hotel rooms in downtown Vancouver should allow 20-30 minutes by car to the U.B.C. campus or 40-60 minutes by city bus. The name of a Vancouver travel agent will be included in a future announcement for those wishing to book hotels or tours through a local agent. SCIENTIFIC PROGRAMME Abstracts for talks should be sent to stone@math.ubc.ca (or Art Stone, 8942 Ganymede Place, Burnaby, B.C. V3J 1A1, CANADA) before May 1, 1997. Please include a title and limit the abstract to half a page or less in length. Please indicate the amount of time you would like (20, 30 or 50 minutes). People will not be asked to speak for more time than they have requested and, indeed, limited time may compel some compression of talks. The total number of speakers may have to be limited as well. SPECIAL EVENTS A discussion on some topic of general interest will take place on Tuesday evening July 15. For those interested there may be hikes (or longer expeditions) organized to take place on the day (or days) immediately following the formal part of the meeting. There is an outdoor Shakespeare Festival in Vancouver from June 10 until September 21. Bard on the Beach presents "The Winter's Tale" at 8PM on July 15, 16, 17 and "Love's Labour's Lost" at 8PM on July 18, 19. Bard on the Peak presents "The Winter's Tale" at the top of Grouse Mountain at 1PM on July 19. Tickets can be obtained through a travel agent. The 20th annual Vancouver Folk Music Festival will be held near the beach, in Jericho Park, on Friday evening July 18, all day Saturday July 19 and all day Sunday July 20. This is an outdoor event and if you plan to go tickets can be bought at the gate either day by day, or for the entire weekend. Those interested in contemporary live theatre, sporting events, etc. should enquire through a travel agent regarding schedules of events or find out on arrival. There are fine restaurants available off campus in addition to the student places on campus. There are several beaches nearby. From cat-dist Wed Feb 5 11:37:42 1997 Received: by mailserv.mta.ca; id AA06832; Wed, 5 Feb 1997 11:36:52 -0400 Date: Wed, 5 Feb 1997 11:36:52 -0400 (AST) From: categories To: categories Subject: Re: question on functors adjoint to their dual Message-Id: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Status: O X-Status: Date: Tue, 4 Feb 1997 15:44:58 -0500 (EST) From: Fred E.J. Linton At 01:29 PM 2/4/97 -0400, you wrote: >I am interested in the following situation: a contravariant functor >adjoint to its own dual, with the unit and counit being the same >morphism, but _not_ an iso. > >The canonical example is the contravariant internal hom on a cartesian >(or just symmetric monoidal) closed category, [(_) -> A] for some >object A. > >My question is: is this typical ... ? I think it *is* typical: if we call the functor in question F , and if we write J for the unit object, then we should learn easily that F will just be [(_) -> F(J)] , i.e., F(J) itself will serve as your A . -- FEJ Linton From cat-dist Wed Feb 5 15:17:17 1997 Received: by mailserv.mta.ca; id AA15523; Wed, 5 Feb 1997 15:16:26 -0400 Date: Wed, 5 Feb 1997 15:16:23 -0400 (AST) From: categories To: categories Subject: Lawvere homepage Message-Id: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Status: RO X-Status: Date: Wed, 5 Feb 1997 14:00:00 -0500 (EST) From: F William Lawvere I now have a homepage, thanks to my son Danilo. At the moment,there is just a directory of my past publications, but with a SUBJECT GUIDE that I hope will be useful. In a few weeks we hope to have more material available. http://www.acsu.buffalo.edu/~wlawvere/index.html Best, Bill From cat-dist Wed Feb 5 20:32:56 1997 Received: by mailserv.mta.ca; id AA18824; Wed, 5 Feb 1997 20:31:56 -0400 Date: Wed, 5 Feb 1997 20:31:56 -0400 (AST) From: categories To: categories Subject: weak n-categories Message-Id: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Status: O X-Status: Date: Wed, 5 Feb 1997 15:10:25 -0800 (PST) From: john baez Here is the abstract of a paper that is now available at my website. If printing it out is a problem (see below) I can mail copies to people. - John Baez ---------------------------------------------------------------------- Higher-Dimensional Algebra III: n-Categories and the Algebra of Opetopes John C. Baez and James Dolan We give a definition of weak n-categories based on the theory of operads. We work with operads having an arbitrary set S of types, or `S-operads', and given such an operad O, we denote its set of operations by elt(O). Then for any S-operad O there is an elt(O)-operad O+ whose algebras are S-operads over O. Letting I be the initial operad with a one-element set of types, and defining I(0) = I, I(i+1) = I(i)+, we call the operations of I(n-1) the `n-dimensional opetopes'. Opetopes form a category, and presheaves on this category are called `opetopic sets'. A weak n-category is defined as an opetopic set with certain properties, in a manner reminiscent of Street's simplicial approach to weak omega-categories. In a similar manner, starting from an arbitrary operad O instead of I, we define `n-coherent O-algebras', which are n times categorified analogs of algebras of O. Examples include `monoidal n-categories', `stable n-categories', `virtual n-functors' and `representable n-prestacks'. We also describe how n-coherent O-algebra objects may be defined in any (n+1)-coherent O-algebra. ----------------------------------------------------------------------- The paper is available in Postscript form on the web at http://math.ucr.edu/home/baez/op.ps The paper is 59 pages long, so this file is rather large. A compressed version is available at http://math.ucr.edu/home/baez/op.ps.Z You can download this and then (on most UNIX systems) type uncompress op.ps.Z to get the Postscript file. If you like ftp, you can also get these by anonymous ftp to math.ucr.edu They are in the directory pub/baez as the files op.ps and op.ps.Z From cat-dist Sun Feb 9 21:04:33 1997 Received: by mailserv.mta.ca; id AA30266; Sun, 9 Feb 1997 21:03:39 -0400 Date: Sun, 9 Feb 1997 21:03:38 -0400 (AST) From: categories To: categories Subject: query Message-Id: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Status: O X-Status: Date: Sat, 8 Feb 1997 15:19:56 -0500 (EST) From: James Stasheff is there a name for a gadget with stict unit strict inverses but multiplcation not always defined and associativity holds when both a(bc) and (ab)c are defined BUT neither bracketing existing implies the other exists references? thanks .oooO Jim Stasheff jds@math.unc.edu (UNC) Math-UNC (919)-962-9607 \ ( Chapel Hill NC FAX:(919)-962-2568 \*) 27599-3250 http://www.math.unc.edu/Faculty/jds May 15 - August 15: 146 Woodland Dr Lansdale PA 19446 (215)822-6707 From cat-dist Mon Feb 10 11:53:50 1997 Received: by mailserv.mta.ca; id AA24853; Mon, 10 Feb 1997 11:52:24 -0400 Date: Mon, 10 Feb 1997 11:52:23 -0400 (AST) From: categories To: categories Subject: Re: query Message-Id: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Status: O X-Status: Date: Mon, 10 Feb 1997 07:50:48 -0500 (EST) From: Peter Freyd I've been talking about paracategories for several years now. But they require some more axioms. And they don't require inverses. From cat-dist Thu Feb 13 13:41:02 1997 Received: by mailserv.mta.ca; id AA05047; Thu, 13 Feb 1997 13:39:14 -0400 Date: Thu, 13 Feb 1997 13:39:13 -0400 (AST) From: categories To: categories Subject: Category Theory and Databases Message-Id: Mime-Version: 1.0 Content-Type: MULTIPART/MIXED; BOUNDARY="=_bajCbBMT4" Content-Id: Status: RO X-Status: This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. Send mail to mime@docserver.cac.washington.edu for more info. --=_bajCbBMT4 Content-Type: TEXT/PLAIN; CHARSET=US-ASCII Content-ID: Date: Thu, 13 Feb 1997 15:12:56 UTC From: Jose I. Bravo I am very interested in the application of Category Theory in the area of Databases. Could anybody help me to obtain references on this subject? Thanks in advance. --=_bajCbBMT4 Content-Type: TEXT/PLAIN; CHARSET=US-ASCII Content-ID: -------------------------------------------------------------------- Jose I. Bravo phone: +34 +22 603306 Dpt. Estadistica, I.O. y Computacion fax: +34 +22 635358 Universidad de La Laguna email: jibravo@ull.es Tenerife (Canary Islands) SPAIN -------------------------------------------------------------------- --=_bajCbBMT4-- From cat-dist Sun Feb 16 15:42:58 1997 Received: by mailserv.mta.ca; id AA13693; Sun, 16 Feb 1997 15:42:08 -0400 Date: Sun, 16 Feb 1997 15:42:08 -0400 (AST) From: categories To: categories Subject: RE: Category Theory and Databases Message-Id: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Status: O X-Status: Date: Sat, 15 Feb 1997 17:51:16 GMT From: MHEBERT@acs.auc.eun.eg The following (and the references in it) may be useful: Volger, H., The semantics of disjunctive deductive databases, LNCS 440, 409-421 Spinger, Berlin 1990. Volger, H., Initial and quasi-initial models of theories, Fund.Inform. 18(1993) 339-362. Michel Hebert From cat-dist Mon Feb 17 10:44:59 1997 Received: by mailserv.mta.ca; id AA11835; Mon, 17 Feb 1997 10:44:04 -0400 Date: Mon, 17 Feb 1997 10:44:04 -0400 (AST) From: categories To: categories Subject: Re: Category Theory and Databases Message-Id: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Status: O X-Status: Date: Mon, 17 Feb 1997 12:07:31 +0000 (GMT) From: David Pym There is some work by John Cartmell. He applied some ideas from his thesis --- about contextual categories, generalized algebraic theories and dependent type theory. The thesis was Oxford, '78, and some of it appeared in the Ann. P. Appl. Logic 32 (1986) 209-243. Unfortunately, the only reference to the databases applications that I can recall just now is: Formalizing the network and hierarchical data models --- an application of categorical logic, LNCS 240, 1986. Thomas Streicher may perhaps know more ? David > Date: Thu, 13 Feb 1997 15:12:56 UTC > From: Jose I. Bravo > > I am very interested in the application of Category Theory in the > area of Databases. Could anybody help me to obtain references on > this subject? From cat-dist Tue Feb 18 16:02:15 1997 Received: by mailserv.mta.ca; id AA22413; Tue, 18 Feb 1997 16:01:09 -0400 Date: Tue, 18 Feb 1997 16:01:09 -0400 (AST) From: categories To: categories Subject: Re: Category Theory and Databases Message-Id: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Status: RO X-Status: Date: Tue, 18 Feb 1997 20:35:22 +0000 From: Zinovy Diskin There are a few papers written by mathematicians, they are rather far from the hot DB problems. There are several papers written by DB theorists, CT is used there as a kind of decoration rather than essentially. There are a few works where CT is really employed for solving real DB problems. In summer of 1994 Boris Kadish and I wrote a declarative text called "Algberaic Graph-Oriented = Category-Theory-Based: Manifesto of categorizing database theory " (its last updated version can be found on ftp: //ftp.cs.chalmers.se/pub/users/diskin/mnfst4.* ), in which there is a list of about 30 titles on CT & DB. The manifesto and other our papers on CT & DB are oriented mainly on DB people but can be of some interest for CT people as well. The machinery we use is a generalization of Makkai's sketches. My last effort in the direction "CT for DB" is the paper "Variable set semantics for generalized sketches: Why ER is more object-oriented than OO" (on ftp: //ftp.cs.chalmers.se/pub/users/diskin/ERvsOO.* ) submitted to 'Data & Knowledge Engineering'. Zinovy Diskin From cat-dist Tue Feb 18 16:02:15 1997 Received: by mailserv.mta.ca; id AA19988; Tue, 18 Feb 1997 15:59:50 -0400 Date: Tue, 18 Feb 1997 15:59:49 -0400 (AST) From: categories To: categories Subject: RE: Category Theory and Databases Message-Id: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Status: RO X-Status: Date: Tue, 18 Feb 1997 11:49:29 GMT From: Khazem A list of papers about category theory and database: I- Papers by Peter Buneman, Val Tannen and others in Univ. of Pennsylvania. Using theory of monads for query languages. see references in their paper: Principle of Programming with Complex objects and Collection Types. TCS 149:3-48, 1995. II- Paper by S.K. LELLAHI, Nicolas Spyratos: Using sketch for modelling data 1- Towards a categorical Data Model supporting structured Object and Inheritance. LCNS NO 504, pp 86-105, 1991 2- Categorical Modelling of database concepts. Technical report Series, FIDE/92/ 38, University of Glasgow 1992 3- Deduction over graphs under constraint: A soundness and completness theorem. Diagramme vol 39, 1993 (edited by: Univ Paris 7, France). 4- Research reports, NOs 619, 410, 908 LRI, Univ. Paris 11 (Orsay), France. 5- Research reports, NO, 93-05 An Algebraic Semantics for Data Modelling under constraints LIPN, Univ. Paris 13 Villetaneuse), France. III- Paper by S.K. LELLAHI, Monads and query languages 1- Towards a Characterization of Bulk types, Research reports, NOs , LIPN, Univ. Paris 13 Villetaneuse), France. 2- Type de collection et Monades. Acte des journees Categories, Algebres, Esquisses et Neo_esquisses, 1994, Univ. de CAEN, France IV- Others 1- E. Lippe & al a) A Category theory approach to coceptual data Modelling, Theorical information and Application, vol 30, nO 1, 1966, pp 31_97. b) Conceptual data modelling from a Categorical Perspective. The Computer Journal, Vol 39, No 3 1966. ------------------------------------------------------- Kazem LELLAHI From cat-dist Tue Feb 18 16:02:16 1997 Received: by mailserv.mta.ca; id AA20710; Tue, 18 Feb 1997 16:02:05 -0400 Date: Tue, 18 Feb 1997 16:02:05 -0400 (AST) From: categories To: categories Subject: CSL '97 second announcement and call for papers Message-Id: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Status: RO X-Status: Date: Tue, 18 Feb 1997 14:58:58 +0100 (MET) From: Uffe Henrik Engberg CSL '97 Annual Conference of the European Association for Computer Science Logic August 23-29, 1997 7 Aarhus, Denmark Second Announcement and Call for Papers CSL is the annual conference of the European Association for Computer Science Logic (EACSL). The conference is intended for computer scientists whose research activities involve logic, as well as for logicians working on topics significant for computer science. Scientific Program August 23-24, 1997: Tutorials on Games and Logic S. Abramsky (Edinburgh): Game Semantics A. E. Emerson (Austin): Games, 5-calculus, and program verification W. Thomas (Kiel), I. Walukiewicz (Warsaw): Determinacy, the Rabin Tree Theorem and its extensions August 25-29, 1997: Invited Lectures and Contributed Papers The list of invited speakers will include: S. Buss (San Diego), H. Comon (Paris), T. Coquand (Gothenburg), M. Hyland (Cambridge), N. Immerman (Amherst), N. Klarlund (Murray Hill), Y. Moschovakis (Los Angeles), L. Pacholski (Wroclaw). Local Organization and Accommodation BRICS, Department of Computer Science, University of Aarhus. Limited financial support for young researchers is available. Inquiries and applications should be sent to csl97@brics.dk. Further information can be found on http://www.brics.dk/CSL97. Submissions Authors are invited to submit a draft or full paper (up to 12 pages) together with a two page abstract. The cover page should include title, authors, and corresponding authors (name, address, phone/fax number, e-mail address). Electronic submissions are encouraged. Submission forms can be obtained from http://www.brics.dk/CSL97/subm.html or by sending an empty message with Subject: submission information to: csl97-subm@brics.dk. Alternatively, five hardcopies should be sent to: Prof. Mogens Nielsen, CSL '97 Department of Computer Science University of Aarhus Phone: +45 8942 3260 Ny Munkegade, Bldg. 540 Fax: +45 8942 3255 DK-8000 Aarhus C, Denmark E-mail: csl97@brics.dk Deadline of Submission: April 15, 1997 Authors will be notified of acceptance for presentation at the conference by June 15, 1997. A preliminary version of the full paper to be submitted to the Proceedings volume (LNCS Springer-Verlag) should be available at the conference. Authors will be notified of acceptance of their paper by December 15, 1997. Program Committee K. Compton (Ann Arbor), J. Flum (Freiburg), J.-Y. Girard (Paris), F. Honsell (Udine), J. W. Klop (Amsterdam), W. Marek (Lexington), M. Nielsen (Aarhus, Vice-chair), P. Pudlak (Prague), E. Robinson (QMW, London), A. Tarlecki (Warsaw), W. Thomas (Kiel, Chair), I. Walukiewicz (Warsaw) EACSL Board E. Bvrger, D. van Dalen, K. Ambos-Spies, K. Meinke, J.Y. Girard, C. Bvhm, B. Buchberger, Y. Gurevich, L. Pacholski The conference is sponsored by BRICS (Basic Research in Computer Science), a Centre of the Danish National Research Foundation From cat-dist Wed Feb 19 11:52:10 1997 Received: by mailserv.mta.ca; id AA15039; Wed, 19 Feb 1997 11:51:36 -0400 Date: Wed, 19 Feb 1997 11:51:36 -0400 (AST) From: categories To: categories Subject: AMS Special session in categories Message-Id: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Status: O X-Status: Date: Wed, 19 Feb 1997 00:16:58 -0500 From: Robert A. G. Seely Mike Barr has asked me to relay the following information (my source was the following URL: ) The pertinent fact of interest to this list is the special session on Category Theory and its Applications which he, Ieke Moerdijk, and Myles Tierney are organizing. For further information, contact the organizers; updates will be posted to this list as appropriate. = rags = -------------------------------------------------------------------------- Notice of AMS Meeting September 26-28, 1997 Montreal, Quebec Canada (1997 Fall Eastern Sectional Meeting) Meeting # 924, Notices Program Issue: October 1997 Deadline for Contributed Papers for consideration in Special Sessions: May 1, 1997 Deadline for Abstract Submission: June 26, 1997 Special Sessions and Invited Addresses Invited Addresses Jacob E. Goodman, City University of New York, City College , Title to be announced Dieter Kotschick, University of Basel, Switzerland , Title to be announced Francois Lalonde, University of Quebec at Montreal , Title to be announced I. Moerdijk, University of Utrecht, Netherlands , Title to be announced Special Session on Category Theory and Its Applications Organizers: Michael Barr, McGill University barr@triples.math.mcgill.ca Ieke Moerdijk, University of Utrecht. Netherlands moerdijk@math.ruu.ne Myles Tierney, Rutgers University tierney@math.rutgers.edu From cat-dist Wed Feb 19 11:52:21 1997 Received: by mailserv.mta.ca; id AA10510; Wed, 19 Feb 1997 11:52:13 -0400 Date: Wed, 19 Feb 1997 11:52:13 -0400 (AST) From: categories To: categories Subject: revised paper available Message-Id: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Status: O X-Status: Date: Wed, 19 Feb 1997 12:17:32 +0100 (MET) From: koslowj@iti.cs.tu-bs.de Hello, A revised version of my article "A convenient category for games and interaction" is available from my home page http://www.iti.cs.tu-bs.de/TI-INFO/koslowj/koslowski.html It better substantiates my claim of last year's workshop Domains II here in Braunschweig that the composition of games I introduced is orthogonal to the established composition of strategies. The abstract is appended at the end. If you had trouble in the past reaching my home page, we did find a faulty entry in a name server last Fall. If the problems persist, please let me know! -- J"urgen %% Abstract for: A convenient category for games and interaction Guided by the familiar construction of the category rel of relations, we first construct an order-enriched category gam . Objects are sets, and 1-cells are games, viewed as special kinds of trees. The quest for identities for the composition of arbitrary trees naturally suggests alternating trees of a specific orientation. Disjoint union of sets induces a tensor product $\otimes$ and an operation --o on gam that allow us to recover the monoidal closed category of games and strategies of interest in game theory. Since gam does not have enough maps, \ie, left adjoint 1-cells, these operations do not have nice intrinsic descriptions in gam . This leads us to consider games with explicit delay moves. To obtain the ``projection'' maps lacking in gam , we consider the Kleisli-category K induced by the functor _+1 on the category of maps in gam . Then we extend gam as to have K as category of maps. Now a satisfactory intrinsic description of the tensor product exists, which also allows us to express --o in terms of simpler operations. This construction makes clear why $\multimap$, the key to the notion of strategy, cannot be functorial on gam . Nevertheless, the composition of games may be viewed as orthogonal to the familiar composition of strategies in a common framework. -- J"urgen Koslowski % If I don't see you no more in this world ITI % I meet you in the next world TU Braunschweig % and don't be late! koslowj@iti.cs.tu-bs.de % Jimi Hendrix (Voodoo Child) From cat-dist Thu Feb 20 14:13:37 1997 Received: by mailserv.mta.ca; id AA09843; Thu, 20 Feb 1997 14:12:43 -0400 Date: Thu, 20 Feb 1997 14:12:42 -0400 (AST) From: categories To: categories Subject: Re: Category Theory and Databases Message-Id: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Status: O X-Status: Date: Wed, 19 Feb 1997 19:01:48 +0000 From: Nick Rossiter At Newcastle University, we have been studying the application of category theory to a number of information system problems, including the formalization of object-relational databases. Further information, including citations to some publications, can be found at: http://www.cs.ncl.ac.uk/people/b.n.rossiter/home.informal/ From cat-dist Fri Feb 21 12:27:35 1997 Received: by mailserv.mta.ca; id AA02828; Fri, 21 Feb 1997 12:26:50 -0400 Date: Fri, 21 Feb 1997 12:26:49 -0400 (AST) From: categories To: categories Subject: Re: Category Theory and Databases Message-Id: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Status: O X-Status: Date: Fri, 21 Feb 1997 11:44:35 +0100 From: Frank Piessens In Leuven, we have studied semantic data-specifications from a categorical perspective. We have studied sketches as a formalism for making semantic data-specifications (somewhat similar to the approach taken by Diskin et al.), and have developed and proved correct a number of interesting algorithms to decide semantical equivalence of such specifications. The following publications describe our work: Frank Piessens, Eric Steegmans. ``Categorical data-specifications'', {\em Theory and Applications of Categories}, Vol. 1, No. 8, 1995, pp. 156--173. Frank Piessens, Eric Steegmans. ``Proving semantical equivalence of data specifications'', accepted for publication in the special issue of {\em The Journal of Pure and Applied Algebra} dedicated to the celebration of Peter Freyd's 60th birthday. Frank Piessens. ``Semantic data specifications: an analysis based on a categorical formalization'', PhD thesis, Dept. of Computer Science, Katholieke Universiteit Leuven, 1996. Frank Piessens. From cat-dist Fri Feb 21 12:27:43 1997 Received: by mailserv.mta.ca; id AA07736; Fri, 21 Feb 1997 12:27:35 -0400 Date: Fri, 21 Feb 1997 12:27:35 -0400 (AST) From: categories To: categories Subject: Locales as "topology-free spaces" Message-Id: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Status: RO X-Status: Date: Fri, 21 Feb 1997 11:34:36 +0000 From: Steve Vickers I am making two papers available as Departmental Research Reports: "Topical Categories of Domains" "Localic Completion of Quasimetric Spaces" Both explore the idea of locales (and, indeed, toposes) as "topology-free spaces". The technique is to work not with frames (point-free topologies) but with presentations of them, understood as propositional geometric theories whose models are the points. (But it is normally more convenient to work with equivalent predicate theories.) Then - * the geometric theory already determines an implicit topology on its models; * any construction of models of one theory out of models of another automatically determines a continuous map (or geometric morphism), just so long as the construction is geometric. In effect, a restriction to geometric mathematics removes the need to treat topology explicitly, hence "topology-free spaces". Apparently, explicit topology is needed to correct the over-credulousness of classical reasoning principles, though in practice the geometric constraints often end up forcing one to reintroduce the normal topological arguments in a different guise. The two papers test the applicability of the idea in the two areas of domain theory and quasimetric spaces. Aside from the "topology-free space" aspects, the papers develop some new results: "Topical Categories of Domains" addresses categorical domain theory and replaces the usual classes of objects and morphisms by toposes classifying them. New general results concerning fixpoints of endo-geometric-morphisms of toposes exploit their intrinsically topological nature to give a simple approach to the solution of domain equations. The paper also gives a summary of the constructive theory of Kuratowski finite sets and establishes some limitations to the Cartesian closedness of Sets. "Localic Completion of Quasimetric Spaces" proposes a construction of locales in completion of quasimetric spaces (using ideas of flatness deriving from Lawvere's enriched category account), studies the powerlocales and shows that a limit map from a locale of Cauchy sequences to the completion is triquotient in the sense of Plewe. Paper copies are available from me; electronic copies are expected to be available shortly in the Department of Computing's Research Report series coordinated by Frank Kriwaczek (frk@doc.ic.ac.uk). Steve Vickers. From cat-dist Tue Feb 25 16:21:54 1997 Received: by mailserv.mta.ca; id AA24146; Tue, 25 Feb 1997 16:19:01 -0400 Date: Tue, 25 Feb 1997 16:19:01 -0400 (AST) From: categories To: categories Subject: PSSL 64 Message-Id: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Status: O X-Status: Date: Tue, 25 Feb 1997 17:39:15 +0100 (MET) From: koslowj@iti.cs.tu-bs.de PERIPATETIC SEMINAR ON SHEAVES AND LOGIC 64th meeting - first announcement The 64th meeting of the seminar will be held at the Department of Theoretical Computer Science of the Technical University in Braunschweig, Germany, over the weekend of May 10-11, 1997. The seminar welcomes talks using or addressing category theory or logic, either explicitly or implicitly, in the study of any aspect of mathematics or science. On Friday, May 9, 13:00, i.e., before the regular seminar, there will be an official Colloquium Talk by Maria Cristina Pedicchio on Exactness and Regularity for Locally Presentable Categories After that, we would like to invite those who arrive here early to visit the Herzog August Library in Wolfenb"uttel with its famous collection of medieval books. Gotthold Ephraim Lessing used to be a librarian there. Braunschweig is located about 60 km East of Hannover and can easily be reached by car or train. The closest airport is in Hannover; the airport bus to the Hannover train station takes about 20 minutes, and the train from there to Braunschweig takes about 40 minutes or less. We will send further information on the location of the seminar, along with details on local travel and accommodation to those who register, at least a week before the meeting. Jiri Adamek J"urgen Koslowski ------------------------------------------------------------------------ Please return to J"urgen Koslowski , preferably before April 13. Postal address: Institut f"ur Theoretische Informatik TU Braunschweig Postfach 3329 D-38023 Braunschweig Germany I intend to come to the 64th meeting of the PSSL in Braunschweig * I intend to give a talk entitled ..................................... * I intend to visit the Herzog August Library on Friday afternoon * Please reserve accommodation for Thursday/Friday/Saturday/Sunday night(s) Name : Address: Email : Phone : *Delete if inapplicable -- J"urgen Koslowski % If I don't see you no more in this world ITI % I meet you in the next world TU Braunschweig % and don't be late! koslowj@iti.cs.tu-bs.de % Jimi Hendrix (Voodoo Child) From cat-dist Thu Feb 27 15:55:12 1997 Received: by mailserv.mta.ca; id AA17192; Thu, 27 Feb 1997 15:53:43 -0400 Date: Thu, 27 Feb 1997 15:53:43 -0400 (AST) From: categories To: categories Subject: Re: Category Theory and Databases Message-Id: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Status: RO X-Status: Date: Wed, 26 Feb 1997 16:12:56 +0000 From: Zinovy Diskin I'd like to add some general words to the recent exchange of references on CT \& DB, and apologize in advance for the long reply. Texts on CT \& DB can be roughly divided into two groups. In the first one there are papers (papers-I) where a certain categorical apparatus is applied to a particular DB theory problem, for example, monads to modeling bulk data types, or the pull-back treatment of relational join operation, or the functorial treatment of relational algebra via indexed Boolean algebras and so on. Papers-II are those which pursue a more fundamental goal of stating an integrated framework in which DB theory (or its major components) can be developed. It may sound strange but it seems that papers-II potentially can be much more useful in practice. Indeed, it is commonly recognized that the entire field of software engineering suffers from lack of suitable specification languages. A particular but remarkable example can be found in the concluding report to a recent high-level workshop (organized by an industry company!) where the abstract Wittgenstein's philosophy was invoked: \begin{quote} ... It is clear that the problem of identifying and resolving semantic heterogeneity in a heterogeneous database environment is far from solved, and that the problem itself is still at the stage of being understood. ... Wittgenstein said long ago that if an idea was worth discussing, then it was worth having a language to discuss it. ...Perhaps, one of the most difficult problems in developing integrated systems is in figuring out what schemas, data, and application code mean. \end{quote} In this context, what is required first of all is a general language which allows to specify basic DB theory concepts like database schema, database state, query etc in a way independent of any specific data model (rather than a single universal data model capturing all other data models). For a DB theorist it seems impossible to speak substantially about database schemas and database states without a specific description of what they are: it appears to be a kind of speaking about nothing. In contrast, for a category theorist such an abstract nonsense is a comfortable environment, the focus is to find a proper compromise between generality and applicability. In this respect papers-II existing today are not very successful: the majority of them are either too abstract to be useful in real DB problems or too fragmentary to state a proper foundation. A categorical idea which seems promising in this respect is that of Makkai's sketches, more exactly, their suitable algebraic generalization. In Makkai's presentation, generalized sketches is a framework for managing logic of diagram predicates, the focus is on their inference. In the DB language, this is nothing but derivation of constraints on data. However, the core of the DB technology is derivation of the very data, that is, in the CT language, the focus is in operations like pull-back, push-out etc. Of course, it is possible to consider, say, the pull-back property as a diagram predicate (as Makkai does) but a more natural and DB-useful view is to treat it as a diagram operation. Then complex generalized sketches which involve several marked diagrams must be considered as complex algebraic terms in the corresponding signature of diagram operations, and some parsing procedure is applicable. A notion of generalized sketch over a signature of diagram predicates and operations can be defined along these lines in parallel to the ordinary notion of logical theory over a signature of predicate and operation symbols. (It appears to be a truly graph-based logic in the spirit of Bagchi and Wells. A preliminary framework of basic definitions is described in the report "Databases as diagram algebras: specifying queries and views via the graph-based logic of sketches" (on ftp: //ftp.cs.chalmers.se/pub/users/diskin/TR9602/*.ps ). \bigskip I study DB for more than five years. It is a very lively, rich and mobile world which significantly influences the modern information technology and culture. However, in the mathematical perspective DB theory is seen as a small campus of the relational data model surrounded by a vast savage forest of various notational and terminological systems without any denotational semantics. In my wanderings in the forest, CT served as a reliable guide and, at last, I have composed the following CT-map of DB: 1) Database schemas (including ER-diagrams and the like) are generalized sketches in one or another signature; 2) Database states are sketch morphisms from schema sketches into topos-like model sketches built over domains of values and data objects; 3) Queries against databases are diagram operations, and query languages are monads over categories of generalized sketches; 4) Databases are Eilenberg-Moore algebras of these monads while views and refinements of database schemas are Kleisly morphisms. 5) Architecture schemas of distributed database systems are metasketches whose nodes are generalized sketches and arrows are their morphisms. I do not want to say that DB theory is an applied category theory: as any other advanced engineering discipline, DB is much richer than one or another formal theory used for modeling engineering concepts. Thus, it is more correct to read statements "A is B" above as "It is useful to view A as B" . Nevertheless, CT-formulation of DB-concepts turned out to be extremely useful in the theory and even practice of DB design. In a sense, relations between CT and software engineering remind those between calculus and mechanics engineering. Thanks for your attention, Zinovy Diskin From cat-dist Thu Feb 27 15:55:17 1997 Received: by mailserv.mta.ca; id AA26091; Thu, 27 Feb 1997 15:54:27 -0400 Date: Thu, 27 Feb 1997 15:54:27 -0400 (AST) From: categories To: categories Subject: Express97 Message-Id: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Status: O X-Status: Date: Wed, 26 Feb 1997 15:19:38 +0100 (MET) From: joachim@sics.se *********************** * E X P R E S S 9 7 * *********************** Preliminary Call for Papers for the 4th Workshop on EXPRESSIVENESS IN CONCURRENCY 8-12 September 1997, Santa Margherita Ligure, Italy Deadline for submissions: 2 MAY 1997 See also: ********************************************** * http://www.sics.se/~joachim/Express97.html * ********************************************** SCOPE This meeting aims at a general understanding of the interconnections and relations between formal systems, ranging from programming languages for concurrency to logics. More specifically, we consider methods to compare concurrent programming concepts, such as imperative programming, logic programming, functional programming, concurrent programming, object-oriented programming, dataflow, and the various combinations thereof, on the basis of their relative expressive power. We also consider associated mathematical formalisms such as process algebras, Petri nets, modal logics, rewrite systems etc. from this point of view. The meeting is mainly intended for active researchers to get together and discuss their latest results and methods. It is also the final meeting of the HCM project EXPRESS, which has been active with this focus since 1994. CO-CHAIRS: Catuscia Palamidessi, University of Genova, Italy email: catuscia@disi.unige.it Joachim Parrow, Royal Inst. of Technology, Sweden email: joachim@it.kth.se INVITED SPEAKERS (list not yet final. The following have accepted): Ralph BACK Ugo MONTANARI Amir PNUELI Vaughan PRATT Colin STIRLING Many speakers from the EXPRESS sites will also attend. The URL above has a tentative list of participants from the project. SUBMISSIONS We seek research or expository papers on at most 15 pages (12pt font) submitted electronically (postscript format) no later than ** 2 MAY 1997 ** Notification of acceptance is 15 June and deadline for final versions is 31 August. Information about the submission procedure will be available soon at http://www.disi.unige.it/person/PalamidessiC/EXPRESS97/submit.html For additional information send email to expr97@venus.disi.unige.it The proceedings will appear as a volume in the Electronic Notes of Theoretical Computer Science. We are currently investigating the possibility of having a special issue of selected papers to appear in a well-established computer science journal. PROGRAMME COMMITTEE Luca Aceto, University of Aalborg, DK Jan Bergstra, University of Amsterdam, NL Eike Best, University of Oldenburg, DE Frank de Boer, University of Utrecth, NL Ilaria Castellani, INRIA Sohia-Antipolis, FR Philippe Darondeau, INRIA Rennes, FR Rocco De Nicola, University of Florence, IT Ursula Goltz, University of Hildesheim, DE Jan Willem Klop, CWI, NL Catuscia Palamidessi (Co-chair), University of Genova, IT Joachim Parrow (Co-chair), Royal Inst. of Technology, SE Frits Vaandrager, University of Nijmegen, NL VENUE The conference will take place at Hotel Regina Elena in Santa Margherita Ligure. This is a 4 stars hotel with private beach and conference facilities, which will also provide accommodation for most of the participants. Santa Margherita Ligure is a beautiful sea resort in Liguria, on the Riviera di Levante. It is very close to Portofino promontory and about 30 km east of Genova. The nearest international airport is in Genova with direct connections to Zurich, Paris, London, Munich and other European towns. Between Santa Margherita Ligure and Genova there are good train connections. From cat-dist Thu Feb 27 15:55:23 1997 Received: by mailserv.mta.ca; id AA10833; Thu, 27 Feb 1997 15:55:18 -0400 Date: Thu, 27 Feb 1997 15:55:18 -0400 (AST) From: categories To: categories Subject: CTCS'97 conference - change of deadline Message-Id: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Status: RO X-Status: Date: Thu, 27 Feb 1997 08:31:31 +0100 From: Eugenio Moggi CATEGORY THEORY AND COMPUTER SCIENCE (CTCS'97) 4-6 SEPTEMBER 1997, S. MARGHERITA LIGURE (GENOA), ITALY URL: "http://www.disi.unige.it/conferences/ctcs97/" The deadline for electronic submission has been postponed to the 4th of March. Please look at the conference URL for the Call for Papers. Best Regards Eugenio Moggi