Date: Wed, 2 Nov 1994 05:36:00 +0400 (GMT+4:00) Subject: subobjects of free objects Date: Mon, 31 Oct 1994 18:20:21 +0000 From: "Prof R. Brown" What results of the form `A sub-X of a free X is free' are known? I am aware of groups, magmas (= set with binary operation), and modules over a principal ideal domain. I'd be interested to hear of structures for which this is either known to be true, or examples where it fails. John Stell There are a lot of counterexamples examples in the topological case. There is also a lot of work on the profinite case (open subgroups of free profinite groups are free profinite). Brown and Hardy proved open subgroups of free topological groups are free topological (various k_{\omega} conditions used) (JLMS (2)10 (1975) 431-440).Sid Morris has a good survey in Categorical Topology (Proceedings Toledo 1983, ed HLBentley et al). I have a paper in Proc AMS 52 (1975) 433-441 giving examples of non projective closed subgroups of the free topological group on [a,b] (e.g. the subgroup generated by {a} and x^2 for x \in [a,b], has \pi_0 = Z_2, which is not free). Ronnie Brown Prof R. Brown Tel: +44 248 382474 School of Mathematics Fax: +44 248 355881 Dean St email: mas010@uk.ac.bangor University of Wales Bangor Gwynedd LL57 1UT UK Date: Wed, 2 Nov 1994 05:39:20 +0400 (GMT+4:00) Subject: Re: sub-structures of free structures Date: Tue, 1 Nov 94 10:09:06 -0600 From: James Madden The discussion and responses on sub-structures of free structures got me thinking about a problem that bothered to me some time a go. Suppose an equational class V has the following property: (1) if A and B are FINITELY GENERATED V-agebras whose coproduct is free, then A and B are both free. Does this imply that V has the prorerty that (2) if A and B are ANY V-agebras whose coproduct is free, then A and B are both free? I proved in 1983 that the variety of vector-lattices (= abelian lattice-ordered groups with order-preserving action by positive real numbers) has (1), using PL topology. (In the variety of vector-lattices, projective does not imply free, so this result has some content.) In fact, if V = vector-lattices, the following is true: (1a) if A and B are ANY V-agebras whose coproduct is FINITELY GENERATED and free, then A and B are both free. BUT, I was never able to show that the variety of vector-lattices has (2). Does (2) follow from (1) or from (1a) by any general theorems of universal algebra, model-theory, etc.? James Madden Date: Wed, 9 Nov 1994 15:56:19 +0400 (GMT+4:00) Subject: Fibrations<-->Adjunctions???? Date: Wed, 9 Nov 1994 19:10:37 +0100 From: Maura Cerioli Hi, I need to use the following result about the equivalence between the existence of a fibration and the existence of a right adjoint to an opportune functor between comma categories: ----------------- Let A and B be categories and let U:A-->B be a functor. Let C denote the comma category A arrow (whose objects are the arrows of A) and let D denote the comma category B over U (whose objects are arrows in B from a generic object b into U(a), together with a). Then U induces a functor V:C-->D, that basically is U (as both objects and arrows in C are arrows in A too) and is defined as follows: * V(f:a-->a')=(U(f):U(a)-->U(a'),a') for each object f:a-->a' in A; * V(g,g')=(U(g),g') for each arrow (g,g'):(f1:a1-->a'1)----->(f2:a2-->a'2) in A. Then U is a fibration iff V has a right adjoint G:D-->C s.t. G;V is the identity on D and the counit of the adjunction is the identity natural transformation. ----------------- Now, I know (or at least I believe) that the result holds, as I have a proof for it; but a collegue said to me that this is a known result and suggested to look at the works by Street in the Sydney Category Seminar. Unfortunately, being quite ignorant about 2categories, I find very hard even to understand in which sense the result I want is there. Does anybody know an easier reference, possibly not involving 2categories? Thanks Maura Maura Cerioli DISI - Dipartimento di Informatica e Scienze dell'Informazione Viale Benedetto XV, 3 16132 Genova ITALY Date: Wed, 9 Nov 1994 15:51:53 +0400 (GMT+4:00) Subject: New papers available by gopher & ftp Date: 8 Nov 1994 20:51:40 GMT From: Charles Wells Three papers are newly available by gopher and by anonymous ftp from Case Western Reserve University: "The categorical theory generated by a limit sketch", by Michael Barr and Charles Wells. This was formerly called "The category of diagrams". "Varieties of mathematical prose" by Atish Bagchi and Charles Wells. This is not about category theory but was referred to in our paper "The logic of sketches" (also available by gopher & ftp). "Extension theories for categories", by Charles Wells. This is an old paper that was never submitted for publication. I have updated the bibliography as far as I can, but would appreciate it if anyone knows of other suitable references. They are available by gopher in both DVI and Postscript form from the host gopher.cwru.edu, path 1/class/mans/math/pub/wells. Most www clients can get gopher files, and some of the can view Postscript files on screen. The files are also available by anonymous ftp from ftp.cwru.edu in the directory math/wells, under the following filenames: "Varieties of mathematical prose": MATHRITE.DVI, MATHRITE.PS "Extension theories for categories": CATEXT.DVI, CATEXT.PS "The categorical theory generated by a limit sketch": DIAGC.DVI, DIAGC.PS "The logic of sketches": LOGSTR.DVI, LOGSTR.PS I would appreciate knowing if anyone has problems downloading these files. -- Charles Wells Department of Mathematics, Case Western Reserve University 10900 Euclid Avenue, Cleveland, OH 44106-7058, USA 216 368 2893 Date: Thu, 10 Nov 1994 12:58:42 +0400 (GMT+4:00) Subject: Re: Fibrations<-->Adjunctions???? Date: Wed, 9 Nov 1994 21:22:16 +0000 (GMT) From: Dusko Pavlovic The result goes back to Claude Chevalley's seminar. (One direction does require the Axiom of Choice.) I think a simple formulation is in J.Gray's paper on fibrations in the proceedings of La Yolla conference, Springer 1965. -- Dusko Pavlovic Date: Thu, 10 Nov 1994 13:00:41 +0400 (GMT+4:00) Subject: cat logic of interactions Date: Wed, 9 Nov 1994 22:10:43 +0000 (GMT) From: Dusko Pavlovic I just remembered that I never announced this paper in which I was trying to learn some concurrency theory. It depends on a note on representation, that used to be its appendix. It will be available soon. The ps-file with A4-format is in papers/Pavlovic on theory.doc.ic.ac.uk; the American format is in pub/pavlovic on triples.math.mcgill.ca. All the best, -- Dusko CATEGORICAL LOGIC OF CONCURRENCY AND INTERACTION I: SYNCHRONOUS PROCESSES by Dusko Pavlovic (August 1994) Abstract. This is a report on a mathematician's effort to understand some concurrency theory. The starting point is a logical interpretation of Nielsen and Winskel's account of the basic models of concurrency. Upon the obtained logical structures, we build a calculus of relations which yields, when cut down by bisimulations, Abramsky's interaction category of synchronous processes. It seems that all interaction categories arise in this way. The obtained presentation uncovers some of their logical contents and perhaps sheds some more light on the original idea of processes as relations extended in time. The sequel of this paper will address the issues of asynchronicity, preemption, noninterleaving and linear logic in the same setting. Date: Thu, 10 Nov 1994 18:45:43 +0400 (GMT+4:00) Subject: Announce paper: Cockett & Seely Date: Wed, 9 Nov 94 22:38:25 EST From: "Robert A. G. Seely" The following paper has been placed on anonymous ftp at triples.math.mcgill.ca, directory /pub/rags/wk_dist_cat Weakly distributive categories by J.R.B. Cockett and R.A.G. Seely Abstract: There are many situations in logic, theoretical computer science, and category theory where two binary operations---one thought of as a (tensor) ``product'', the other a ``sum''---play a key role. In distributive and *-autonomous categories these operations can be regarded as, respectively, the and/or of traditional logic and the times/par of (multiplicative) linear logic. In the latter logic, however, the distributivity of product over sum is conspicuously absent: this paper studies a ``linearization'' of that distributivity which is present in both case. Furthermore, we show that this weak distributivity is precisely what is needed to model Gentzen's cut rule (in the absence of other structural rules) and can be strengthened in two natural ways to generate full distributivity and *-autonomous categories. This is the journal version of the similarly named paper appearing in the Proceedings of the Durham conference (1991): M.P. Fourman, P.T. Johnstone, A.M. Pitts, eds., Applications of Categories to Computer Science, London Mathematical Society Lecture Note Series 177 (1992) 45 - 65. This version is to appear in the Journal of Pure and Applied Algebra. The paper has been rewritten, including more details and several examples, including shifted tensors, Span categories, and categories of modules of a bialgebra. Date: Thu, 10 Nov 1994 18:50:26 +0400 (GMT+4:00) Subject: Announce paper: Mendler, Panangaden, Scott, & Seely Date: Wed, 9 Nov 94 22:40:42 EST From: "Robert A. G. Seely" The following paper has been placed on anonymous ftp at triples.math.mcgill.ca in directory (file) /pub/rags/ccp/mpss.* A Logical View of Concurrent Constraint Programming by Nax Paul Mendler Prakash Panangaden P.J. Scott R.A.G. Seely Abstract; The Concurrent Constraint Programming paradigm has been the subject of growing interest as the focus of a new paradigm for concurrent computation. Like logic programming it claims close relations to logic. In fact these languages _are_ logics in a certain sense that we make precise in this paper. In recent work it was shown that the denotational semantics of determinate concurrent constraint programming languages forms a categorical structure called a hyperdoctrine, which is used as the basis of the categorical formulation of first order logic. What this connection shows is the combinators of determinate concurrent constraint programming can be viewed as logical connectives. In the present work we extend these ideas to the operational semantics of these languages and thus make available similar analogies for a much broader variety of languages including the indeterminate concurrent constraint programming languages and concurrent block-structured imperative languages. \begin{BTW} In the same directory you will find the earlier paper dealing with the denotational semantics (psss*). This paper has appeared: P. Panangaden, V. Saraswat, P. J. Scott, R. A. G. Seely, A Hyperdoctrinal View of Concurrent Constraint Programming, in J.W. de Bakkee et al, eds. Semantics: Foundations and Applications; Proceedings of REX Workshop, Beekbergen, The Netherlands, June 1992. Springer Lecture Notes in Comp. Science, 666 (1993) pp. 457 -- 476. \end{BTW} Date: Thu, 10 Nov 1994 18:54:05 +0400 (GMT+4:00) Subject: Re: Fibrations<-->Adjunctions???? Date: Thu, 10 Nov 1994 09:00:42 -0500 From: Jim Otto (the message being replied to is appended.) dear Maura Cerioli yes, the Street paper is hard to read. but he refers to a paper of Gray's which has the result you mention. in fact Gray credits it to a manuscript of Chevalley's which was lost in the mail. while i didn't read your description of the result, the way i think of it is as follows. you have a functor p: E --> B this induces a functor (with comma category B/p relative to id: B --> B <-- E :p and with 2 the ordinal) p.: E^2 --> B/p which takes `paths in E' to `paths in B with the to end in E remembered' then (modulo the axiom of choice) p is a fibration iff p. has a right adjoint c. with identity couint. c. is then a cleavage. this unfolds (viewing c. as terminal objects in comma categories) to the usual elementary definition in terms of cartesian maps. Gray says p. is rari, i.e. has a right adjoint right inverse. one can show that this isn't weaker. as i recall, Street's definition is weaker in order to be more invariant. (cod: B^2 --> B is an important example. then c. is pull-back.) actually i need fibrations in 2-categories of monoidal categories. note that, in cat the 2-category of categories, E^2 is the comma category E/E (relative to id: E --> E <-- E :id). further, still in cat, E^2 is the cotensor 2 -o E. but in any 2-category, finite weighted limits, including comma objects, can be built up from cotensors with 2 and (2-) terminal objects and pull-backs. to help you read Street, i now define cotensor with 2. 2-categories have hom categories rather than hom sets. 2 -o E is defined by isomorphisms hom(W, 2 -o E) iso 2 -o hom(W, E) (2-) natural in W. (sometimes such isomorphisms don't exist, but such equivalences do.) bon jour, Jim Otto >Date: Wed, 9 Nov 1994 19:10:37 +0100 >From: Maura Cerioli > >Hi, >I need to use the following result about the equivalence between the >existence of a fibration and the existence of a right adjoint to >an opportune functor between comma categories: >----------------- >Let A and B be categories and let U:A-->B be a >functor. >Let C denote the comma category A arrow (whose objects are the arrows >of A) >and >let D denote the comma category B over U (whose objects are arrows in B >from a generic object b into U(a), together with a). >Then U induces a functor V:C-->D, that basically is U (as both objects >and arrows in C are arrows in A too) >and is defined as follows: >* V(f:a-->a')=(U(f):U(a)-->U(a'),a') for each object > f:a-->a' in A; >* V(g,g')=(U(g),g') for each arrow > (g,g'):(f1:a1-->a'1)----->(f2:a2-->a'2) in A. > >Then U is a fibration iff V has a right adjoint G:D-->C s.t. >G;V is the identity on D and the counit of the adjunction is >the identity natural transformation. >----------------- >Now, I know (or at least I believe) that the result holds, as >I have a proof for it; but a collegue said to me that this is >a known result and suggested to look at the works by Street >in the Sydney Category Seminar. >Unfortunately, being quite ignorant about 2categories, I find very >hard even to understand in which sense the result I want is there. > >Does anybody know an easier reference, possibly not involving >2categories? Date: Fri, 11 Nov 1994 11:05:19 +0400 (GMT+4:00) Subject: CTCS-6 Date: Fri, 11 Nov 1994 18:06:39 +1100 From: D.Pitt@mcs.surrey.ac.uk Preliminary Announcement and Call for Papers CATEGORY THEORY AND COMPUTER SCIENCE CTCS-6 7th-11th August 1995. University of Cambridge, UK. The sixth of the biennial conferences on Category Theory and Computer Science is to be held in Cambridge in 1995, in conjunction with the third Cambridge Summer Meeting in Category Theory. 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 recognised that the area is highly interdisciplinary and the organising 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. Previous meetings have been held in Guildford (Surrey), Edinburgh, Manchester, Paris and Amsterdam. It is anticipated that the proceedings will be published by Springer in the LNCS series. IMPORTANT DATES Submission of papers February 1, 1995 Notification of acceptance April 14, 1995 Final papers due June 1, 1995 SUBMISSION OF PAPERS. Authors should send 5 hard copies of a draft paper (maximum of 20 pages) to Dr. David Pitt, Department of Mathematical and Computing Sciences, University of Surrey, Guildford, Surrey, GU2 5XH, United Kingdom. LOCAL ARRANGEMENTS Registration forms for the joint conference will be available nearer to the date. Dr. Peter Johnstone, Department of Pure Mathematics and Mathematical Statistics, 16 Mill Lane, Cambridge, CB2 1SB, United Kingdom. Organising and programme committee: S. Abramsky, P.-L. Curien, P. Dybjer, P. Johnstone, G. Longo, G. Mints, J. Mitchell, E. Moggi, D. Pitt, A. Pitts, A. Poigne, D. Rydeheard, F-J. de Vries, E. Wagner. Date: Sat, 12 Nov 1994 10:48:09 +0400 (GMT+4:00) Subject: Colimits in categories of diagrams Date: Fri, 11 Nov 1994 13:57:32 -0800 From: Y V Srinivas Do (finite) colimits exist in categories of diagrams? Here are the definitions of the terms used above. A diagram of shape S in a category C is a functor D: S -> C. A covariant diagram morphism from D1: S1 -> C to D2: S2 -> C is a pair consisting a shape morphism (functor) sm: S1 -> S2 and a natural transformation mu: D1 -> D2 o sm. A contravariant diagram morphism is similar except that the direction of the natural transformation is opposite. We thus get two categories of diagrams in C (of all shapes). Mac Lane calls these "super comma categories" (p.111). Now, the question reads: given that (finite) colimits exist in C, do (finite) colimits exist in the two categories of diagrams in C? I haven't been able to come up with a construction or a proof that colimits don't exist. I appreciate any help you can provide on this matter. Also, I would like to know if there are related results, e.g., with limits. - srinivas ======== Y. V. Srinivas E-mail: srinivas@kestrel.edu Kestrel Institute Phone: (415) 493-6871 3260 Hillview Avenue Fax: (415) 424-1807 Palo Alto, CA 94304 Date: Sun, 13 Nov 1994 11:05:24 +0400 (GMT+4:00) Subject: Re: Colimits in categories of diagrams Date: Sat, 12 Nov 1994 21:13:19 -0400 From: Richard Wood > Date: Fri, 11 Nov 1994 13:57:32 -0800 > From: Y V Srinivas > > > Do (finite) colimits exist in categories of diagrams? > > Here are the definitions of the terms used above. > > A diagram of shape S in a category C is a functor D: S -> C. > > A covariant diagram morphism from D1: S1 -> C to D2: S2 -> C is a pair > consisting a shape morphism (functor) sm: S1 -> S2 and a > natural transformation mu: D1 -> D2 o sm. > > A contravariant diagram morphism is similar except that the direction > of the natural transformation is opposite. > > We thus get two categories of diagrams in C (of all shapes). > Mac Lane calls these "super comma categories" (p.111). > > Now, the question reads: given that (finite) colimits exist in C, do > (finite) colimits exist in the two categories of diagrams in C? > > I haven't been able to come up with a construction or a proof that > colimits don't exist. I appreciate any help you can provide on this > matter. Also, I would like to know if there are related results, e.g., > with limits. > > - srinivas In my thesis, Dalhousie 1976, I used a (2-)category of diagrams of the kind that you describe, with C=set. The 2-functor cat--->CAT which sends S to set^(S^op) gives rise to a fibration, say P:D_--->cat, and the objects of D_ are evidently diagrams in set of variable shape. If you regard such an object, D:S^op--->set, as a discrete fibration, say D'--->S, then it is straightforward to describe a 2-fully faithful 2-functor, I:D_--->cat^2 . Now codomain:cat^2--->cat is itself a fibration over cat and the inclusion I is a 2-functor over cat. I has a left adjoint, L, that preserves finite products, from which it follows that D_ is complete, cocomplete and cartesian closed, as a 2-category. By examining the nature of these constructions for my D_ you should be able to find what you need of a general C to answer your question. Well, to continue somewhat, P above clearly preserves limits but it also preserves colimits because the adjunction L-|I is an adjunction over cat. This should help to get started on the general problem. In fact, P preserves exponentiation too. (Pseudo-)category objects in D_ are interesting. Necessarily, they give rise to pseudo-category objects in cat. If, for example, V is a monoidal category then P-over the "category object" VxV--->V<---1 in cat are precisely the set^(V^op)-categories, where the monoidal structure of set^(V^op) is Brian Day's (universal) convolution structure. But there are many other "category objects" in cat that can be constructed from V and its monoidal data. Assembling these and looking at their inverse image in D_ allows one to construct a variant of the Pare-Schumacher theory of indexed categories that is useful when a given monoidal structure on the base for indexing is needed for multiply indexed families. RJ Wood Date: Mon, 14 Nov 1994 17:15:37 +0400 (GMT+4:00) Subject: papers on internal categories ??? Date: Mon, 14 Nov 1994 17:55:48 +0100 (MET) From: Wojciech Zaborowski Hi everyone in 'categories' ! I found only a few pages related in Johnstone's Topos theory'. I am interested in serious introduction to 'internal categories'. I am especially looking for: 1: full systematic internalization of all fundamental concepts of category theory, including natural transformations, limits and adjoints 2: books, papers etc. developing classic theories on such abstract (internal) level Does anyone enjoy playing with 'internal' too ? From rrosebru@nimble.mta.ca Tue Nov 15 10:28:54 1994 Date: Mon, 14 Nov 1994 18:39:26 -0400 (AST) Subject: Re: papers on internal categories ??? Date: Tue, 15 Nov 1994 08:54:47 +1100 From: Ross Street >I am interested in serious introduction to 'internal categories'. Ross Street, Cosmoi of internal categories, Transactions American Math. Soc. 258 (1980) 271-318; MR82a:18007 could be of interest. --Ross id AA17208; Tue, 15 Nov 1994 10:20:09 -0400 Date: Tue, 15 Nov 1994 10:17:39 -0400 (AST) Subject: Re: papers on internal categories ??? Date: 15 Nov 1994 14:00:52 GMT From: cxm7@po.cwru.edu > Date: Mon, 14 Nov 1994 17:55:48 +0100 (MET) > From: Wojciech Zaborowski > > Hi everyone in 'categories' ! > > I found only a few pages related in Johnstone's Topos theory'. > I am interested in serious introduction to 'internal categories'. > I am especially looking for: > 1: full systematic internalization of all fundamental concepts of category > theory, including natural transformations, limits and adjoints > 2: books, papers etc. developing classic theories on such abstract (internal) > level > Does anyone enjoy playing with 'internal' too ? > There is a lot in Johnstone's few pages. I also cover this, making it look as much like naive category theory as I could, in chapter 20 of my book _Elementary categories, elementary toposes_ (Oxford 1992). This book is due out in paperback soon. And you should look at Benabou "Fibred categories and the foundations of naive category theory" (Jour. Symbolic Logic 50, 1985, 10-37) and Johnstone and Pare _Indexed categories_, Springer Lecture Notes in Math 661. Colin McLarty id AA27810; Tue, 15 Nov 1994 19:26:10 -0400 Date: Tue, 15 Nov 1994 19:23:31 -0400 (AST) Subject: history question: Grothendieck universes Date: Tue, 15 Nov 94 10:05:59 CST From: Juergen Koslowski Could someone please tell me where the term "Grothendieck universes" comes from? Some books connect Grothendieck's name with this particular approach to avoid set-theoretical difficulties, others don't. What is the current status on these foundational matters anyway? Has anything else emerged besides MacLanes one universe approach, or Feferman's use of reflection principles? best regards, J"urgen -- J"urgen Koslowski | If I don't see you no more in this world | I meet you in the next world koslowj@math.ksu.edu | and don't be late! nhabkosl@rrzn-user.uni-hannover.de | Jimi Hendrix (Voodoo Child) id AA00424; Tue, 15 Nov 1994 21:42:14 -0400 Date: Tue, 15 Nov 1994 19:27:57 -0400 (AST) Subject: Announcement Date: Tue, 15 Nov 94 15:27:16 EST From: Michael Makkai This is to announce two papers, "Avoiding the axiom of choice in general category theory" and "Generalized sketches as a framework for completeness theorems" both by M. Makkai, McGill University. Both papers are revised versions of ones with identical titles; the original versions were produced about a year ago. Both papers will appear in the Journal of Pure and Applied Algebra. Unfortunately, they are not available electronically. If you are interested in obtaining copies, please send your request to Makkai@triples.math.mcgill.ca . The abstracts of the papers follow. ABSTRACT of "Avoiding the axiom of choice in general category theory", by M. Makkai, McGill University: "The notion of anafunctor is introduced. An anafunctor is, roughly, a "functor defined up to isomorphism". Anafunctors have a general theory paralleling that of ordinary functors; they have natural transformations, they form categories, they can be composed, etc. Anafunctors can be saturated, to ensure that any object isomorphic to a possible value of the anafunctor is also a possible value at the same argument object. The existence of anafunctors in situations when ordinarily one would use choice is ensured without choice; e.g., for a category which has binary products, but not specified binary products, the anaversion of the product functor is canonically definable, unlike the ordinary product functor that needs the axiom of choice. When the composition functors in a bicategory are changed into anafunctors, one obtains anabicategories. In the standard definitions of bicategories such as the monoidal category of modules over a ring, or the bicategory of spans in a category with pullbacks, and many others, one uses choice; the anaversions of these bicategories have canonical definitions. The overall effect is an elimination of the axiom of choice, and of non-canonical choices, in large parts of general category theory. To ensure the Cartesian closed character of the bicategory of small categories, with anafunctors as 1-cells, one uses a weak version of the axiom of choice, which is related to A. Blass' axiom of Small Violations of Choice ("Injectivity, projectivity, and the axiom of choice", Trans. Amer. Math. Soc. 255(1979), 31-59)." ABSTRACT of "Generalized sketches as a framework for completeness theorems", by M. Makkai, McGill University: "A generalized concept of sketch is introduced. Because of their role, morphisms of (generalized) sketches are called sketch-entailments. A sketch is said to satisfy a sketch-entailment if the former is injective relative to the latter in the standard sense; the models of a set R of sketch-entailments are the sketches satisfying all members of R . R logically implies a sketch-entailment s if every model of R is also a model of {s} . A deductive calculus is introduced in which s is deducible from R iff R logically implies s (General Completeness Theorem, GCT). A large number of examples of kinds of structured category is presented showing that the structured categories are selected from among the corresponding generalized sketches as the models of a set of sketch-entailments. As a consequence, the sketch-entailments satisfied by all structured categories of a given kind are exactly the ones that are deducible from a certain, usually finite, set of axioms. In the finitary case, which is the only one considered in detail in the paper, the notion of deduction is effective, and straightforwardly implementable on a computer. One obtains Specific Completeness Theorems (SCT's), each of which asserts that the exactness properties (certain kinds of sketch-entailments) that hold in a specific class of structured categories coincide with the ones that are deducible from a given set of axioms. Each of these specific completeness theorems is deduced from the GCT, and a particular Representation Theorem (RT); RT's are a well-known class of results in categorical logic. The concepts of Compactness and of Abstract Completeness are introduced, and shown to correspond to the same-named concepts in logics in the usual symbolic form, via a translation between the sketch-based syntax and semantics on the one hand, and the Tarskian syntax and semantics on the other. The sketch-based concepts are available for several logics defined categorically for which there are no available symbolic presentations." id AA00518; Tue, 15 Nov 1994 21:44:59 -0400 Date: Tue, 15 Nov 1994 19:29:48 -0400 (AST) Subject: Announcement Date: Tue, 15 Nov 94 15:27:16 EST From: Michael Makkai This is to announce two papers, "Avoiding the axiom of choice in general category theory" and "Generalized sketches as a framework for completeness theorems" both by M. Makkai, McGill University. Both papers are revised versions of ones with identical titles; the original versions were produced about a year ago. Both papers will appear in the Journal of Pure and Applied Algebra. Unfortunately, they are not available electronically. If you are interested in obtaining copies, please send your request to Makkai@triples.math.mcgill.ca . The abstracts of the papers follow. ABSTRACT of "Avoiding the axiom of choice in general category theory", by M. Makkai, McGill University: "The notion of anafunctor is introduced. An anafunctor is, roughly, a "functor defined up to isomorphism". Anafunctors have a general theory paralleling that of ordinary functors; they have natural transformations, they form categories, they can be composed, etc. Anafunctors can be saturated, to ensure that any object isomorphic to a possible value of the anafunctor is also a possible value at the same argument object. The existence of anafunctors in situations when ordinarily one would use choice is ensured without choice; e.g., for a category which has binary products, but not specified binary products, the anaversion of the product functor is canonically definable, unlike the ordinary product functor that needs the axiom of choice. When the composition functors in a bicategory are changed into anafunctors, one obtains anabicategories. In the standard definitions of bicategories such as the monoidal category of modules over a ring, or the bicategory of spans in a category with pullbacks, and many others, one uses choice; the anaversions of these bicategories have canonical definitions. The overall effect is an elimination of the axiom of choice, and of non-canonical choices, in large parts of general category theory. To ensure the Cartesian closed character of the bicategory of small categories, with anafunctors as 1-cells, one uses a weak version of the axiom of choice, which is related to A. Blass' axiom of Small Violations of Choice ("Injectivity, projectivity, and the axiom of choice", Trans. Amer. Math. Soc. 255(1979), 31-59)." ABSTRACT of "Generalized sketches as a framework for completeness theorems", by M. Makkai, McGill University: "A generalized concept of sketch is introduced. Because of their role, morphisms of (generalized) sketches are called sketch-entailments. A sketch is said to satisfy a sketch-entailment if the former is injective relative to the latter in the standard sense; the models of a set R of sketch-entailments are the sketches satisfying all members of R . R logically implies a sketch-entailment s if every model of R is also a model of {s} . A deductive calculus is introduced in which s is deducible from R iff R logically implies s (General Completeness Theorem, GCT). A large number of examples of kinds of structured category is presented showing that the structured categories are selected from among the corresponding generalized sketches as the models of a set of sketch-entailments. As a consequence, the sketch-entailments satisfied by all structured categories of a given kind are exactly the ones that are deducible from a certain, usually finite, set of axioms. In the finitary case, which is the only one considered in detail in the paper, the notion of deduction is effective, and straightforwardly implementable on a computer. One obtains Specific Completeness Theorems (SCT's), each of which asserts that the exactness properties (certain kinds of sketch-entailments) that hold in a specific class of structured categories coincide with the ones that are deducible from a given set of axioms. Each of these specific completeness theorems is deduced from the GCT, and a particular Representation Theorem (RT); RT's are a well-known class of results in categorical logic. The concepts of Compactness and of Abstract Completeness are introduced, and shown to correspond to the same-named concepts in logics in the usual symbolic form, via a translation between the sketch-based syntax and semantics on the one hand, and the Tarskian syntax and semantics on the other. The sketch-based concepts are available for several logics defined categorically for which there are no available symbolic presentations." id AA19746; Wed, 16 Nov 1994 18:50:04 -0400 Date: Wed, 16 Nov 1994 18:45:02 -0400 (AST) Subject: Availability of new paper by ftp Date: Wed, 16 Nov 94 16:56:03 +1100 From: Max Kelly A new preprint "On localization and stabilization for factorization systems", by Carboni, Janelidze, Kelly, and Pare', is available in our ftp site at the address maths.su.oz.au (= 129.78.68.2), in the directory sydcat/papers/kelly, under the titles cjkp.dvi or cjkp.ps; there is also cjkp.tex, but that requires two macros - namely diagrams.tex and kluwer.sty. The paper contains new ideas, but also self-contained introductions to several areas with which some may be unfamiliar: namely factorization systems, descent theory, Galois theory, Eilenberg's monotone-light factorization for maps between compact hausdorff spaces, hereditary torsion theories for abelian categories, the category of finite families of objects of a given category, and the (separable, purely-inseparable) factorization for field extensions. What ways are there of constructing a factorization system (E, M) on a category C ? One simple one is to start with a full reflective subcategory X of C, and to take E to consist of the maps inverted by the reflexion. Of course, this (E, M) doesn't have E pullback-stable except in the special case where X is a LOCALIZATION of C. We examine another general process, which leads to an (E, M) with E stable when it succeeds. We start from ANY factorization system (E, M), and define new classes thus: a map lies in E' if EACH of its pullbacks lies in E; and it lies in M* if SOME pullback of it along an effective descent map lies in M. Note the connexion with Galois theory, in Janelidze's categorical formulation of it: if the (E, M) we begin with arises as above from a reflective full subcategory, the class M* consists of what Janelidze calls the COVERINGS (or, in some contexts, the CENTRAL EXTENSIONS). It is not always the case that (E', M*) is a factorization system; we give necessary and sufficient conditions for it to be so, and apply these to three major examples: Eilenberg's factorization above, certain factorizations connected to hereditary torsion theories, and a new factorization system for finite-dimensional algebras over a field that generalizes (separable, purely-inseparable) factorization for field extensions. Regards to all - Max Kelly. ps: For those without electronic access, a limited number of printed copies will shortly be available; please request them soon, so that we can alert the printer. Max Kelly. id AA29976; Thu, 17 Nov 1994 10:09:15 -0400 Date: Thu, 17 Nov 1994 10:06:54 -0400 (AST) Subject: Re: history question: Grothendieck universes Date: Wed, 16 Nov 94 10:44:44 EST From: Ernie Manes J"urgen: I don't remember for sure since it's been more than 20 years, but I'm of the opinion that Grothendieck invented his universes to deal with functor categories without antinomies. I would start with Grothendieck and Verdier, Springer Lecture Notes 269-70, 1972 in articles by them mentioning the word "topos". egm id AA00362; Thu, 17 Nov 1994 10:19:06 -0400 Date: Thu, 17 Nov 1994 10:16:59 -0400 (AST) Subject: The categorical theory generated by a limit sketch Date: Wed, 16 Nov 1994 15:20:51 -0500 From: Charles F. Wells About two weeks ago I announced the availability of a paper The categorical theory generated by a limit sketch by Michael Barr and Charles Wells by gopher from gopher.cwru.edu and by ftp from ftp.cwru.edu. I have discovered that the copy I posted was not the latest version. The latest version has now been posted. The differences are correction of a few minor errors plus some additional references. -- Charles Wells, Department of Mathematics, Case Western Reserve University 10900 Euclid Avenue, Cleveland OH 44106-7058, USA Phone 216 368 2880 or 216 774 1926 FAX 216 368 5163 id AA05200; Thu, 17 Nov 1994 14:22:24 -0400 Date: Thu, 17 Nov 1994 10:10:15 -0400 (AST) Subject: Re: history question: Grothendieck universes Date: Wed, 16 Nov 1994 11:20:42 -0500 From: Jim Otto hi Juergen it's good to see you're around. for some idea of what i'm up to you might see ftp://triples.math.mcgill.ca/pub/otto/home.html here's some thoughts on 1. universes in practice 2. what is needed 3. the hierarchy paradox 1. one has functor P: set^o --> set X |-> 2^X and adjunction X --> P Y in set ------------------- X x Y --> 2 in set ------------------- Y --> P X in set ------------------- P X --> Y in set^o with unit n: id --> P^2 thus one has meta-function V: ordinals --> sets by 1. V(0) = {} 2. n(V(i)): V(i) --> V(i+1) = P^2 V(i) 3. colimit at limit ordinals then, for limit ordinals i > omega, the sets and functions in V(i) form a topos with NNO. and, for (strongly) inaccessible cardinals i, the V(i) form Grothendieck universes. e.g. see Makkai-Pare as well as Jech or Kunen. 2. one needs big enough colimits to construct e.g. (weak) reflectors to orthogonality and injectivity classes in categories of presheaves. e.g. see Adamek-Rosicky as well as work by Makkai on sketches. 3. in Rose, subrecursion, one finds that n+1 nested `for' loops are needed to reason deterministically about n > 1 nested `for' loops. yet humans reason about themselves, and living creatures reproduce. i conjecture, from work on interactive proof, that it takes probability and residual error to resolve the hierarchy paradox. bon jour, Jim Otto id AA04898; Thu, 17 Nov 1994 14:08:37 -0400 Date: Thu, 17 Nov 1994 10:13:24 -0400 (AST) Subject: Re: history question: Grothendieck universes Date: Wed, 16 Nov 1994 11:41:49 -0500 (EST) From: MTHISBEL@ubvms.cc.buffalo.edu <> I don't have the Grothendieck reference, but it is not attributed to him by accident. Hopefully someone will supply particulars. I enter this to observe (1) One other thing that has emerged is Blass' position, that it doesn't matter (assuming we wish to do mathematics, not theory of languages). That is clearly and effectively stated by Barr and Wells in the preface or whatever it is to . Note further that this treatment of the is in the spirit of Grothendieck. MacLane, sorry, Mac Lane is in the spirit of Plato: the one real universe is out there and we should be discovering its properties. It has more impressive adherents than Plato, e.g. G"odel, but it is not viable. John Isbell id AA09035; Thu, 17 Nov 1994 17:09:01 -0400 Date: Thu, 17 Nov 1994 17:05:17 -0400 (AST) Subject: processes and irredundant trees Date: Thu, 17 Nov 1994 16:28:43 +0000 (GMT) From: Dusko Pavlovic The promised companion to the paper I announced last week is now available. The first version, which I gave to some people, actually CONTAINED AN ERROR --- so please download this version if you have an old copy. The file is CCPS.ps, and can be downloaded either from triples.math.mcgill.ca, or from theory.doc.ic.ac.uk. Regards, -- Dusko CONVENIENT CATEGORIES OF PROCESSES AND SIMULATIONS by Dusko Pavlovic Abstract. We show that irredundant trees, used by Dana Scott in the early sixties, can be used as canonical representants of the bisimilarity classes of automata (or of transition systems). Simulations then boil down to tree morphisms. Along the same lines, the categories of processes modulo the observational and the branching congruences, with the suitable simulations as morphisms again, are shown to be isomorphic with certain subcategories of the category of irredundant trees. id AA10129; Sat, 19 Nov 1994 12:37:18 -0400 Date: Sat, 19 Nov 1994 12:28:27 -0400 (AST) Subject: whoops ... Date: Fri, 18 Nov 94 19:39:36 EST From: Michael Makkai Today (November 18th), a certain (essentially unknown) number of messages that have arrived since yesterday afternoon got erased from my mailfile before I had a chance of reading them. So, if you have made a request concerning the two papers I recently announced, and if you have not received on e-mail an acknowledgement from me, then please repeat your request. Sorry for the inconvenience. Cheers: Michael Makkai id AA07757; Wed, 23 Nov 1994 22:30:27 -0400 Date: Wed, 23 Nov 1994 22:26:17 -0400 (AST) Subject: TLCA '95 : Programme ---------- Forwarded message ---------- Date: Tue, 22 Nov 1994 11:28:12 +0000 Subject: TLCA '95 : Programme \documentstyle{article} \begin{document} \newcommand{\Paper}[2] {{\it #1},$\;${#2}} \title{Programme\\ International Conference on \\ Typed Lambda Calculi and Applications\\ {\normalsize Edinburgh, April 10th - 12th, 1995}} \author{}\date{} \maketitle \begin{tabbing} {\bf MONDAY}\\ Morning Session Chaired by: M.~Dezani\\ {\bf Theory of Reduction and Conversion}\\ 9.00 \Paper{Typed $\lambda$-calculi with explicit substitutions may not terminate} {P.A.~Mellies}\\ 9.30 \Paper{Comparing $\lambda$-calculus translations in sharing graphs} {A.~Asperti, C.~Laneve}\\ 10.00 Coffee\\ 10.30 \Paper{Typed operational semantics}{H.~Goguen}\\ 11.00 \Paper{An explicit eta rewrite rule} {D. Briaud}\\ 11.30 \Paper{$\beta\eta$-equality for coproducts} {N.~Ghani} \\ \\ 12.00 Lunch \\ \\ Afternoon Session Chaired by: G.~Plotkin\\ {\bf Semantics I}\\ 2.00 \= {\it A fully abstract translation between a $\lambda$-calculus with reference types and }\\ \> {\it standard ML,} {E.~Ritter, A.M.~Pitts}\\ 2.30 \Paper{Final semantics for untyped $\lambda$-calculus} {F.~Honsell, M.~Lenisa} \\ 3.00 Tea \\ {\bf Categorical Semantics}\\ 3.30 \Paper{What is a categorical model of intuitionistic linear logic?} {G.M.~Bierman} \\ 4.00 \= {\it Categorical semantics of the call-by-value $\lambda$-calculus,}\\ \> {A.~Pravato, S.~Ronchi della Rocca, L.~Roversi}\\ 4.30 \Paper{Categorical completeness results for the simply-typed $\lambda$-calculus} {A.K.~Simpson} \\ \end{tabbing} \newpage \begin{tabbing} \\ {\bf TUESDAY}\\ Morning Session Chaired by: H.~Barendregt\\ {\bf Type Theory I}\\ 9.00 \Paper{Untyped $\lambda$-calculus with relative typing} {M.R.~Holmes}\\ 9.30 \Paper{Basic properties of data types with inequational refinements} {H.~Kondoh} \\ 10.00 Coffee\\ 10.30 \Paper{Extensions of pure type systems} {G.~Barthe}\\ 11.00 \Paper{A simple calculus of exception handling} {P.~de Groote}\\ {\bf Proof Theory}\\ 11.30 \Paper{Strict functionals for termination proofs} {J.~van de Pol, H.~Schwichtenberg} \\ \\ 12.00 Lunch\\ \\ Afternoon Session Chaired by: F.~Honsell\\ {\bf Semantics II}\\ 2.00 \Paper{A simplification of Girard's paradox} {A.J.~Hurkens}\\ 2.30 \= {\it A realization of the negative interpretation of the Axiom of Choice},\\ \> {S.~Berardi, M.~Bezem, T.~Coquand}\\ 3.00 Tea\\ 3.30 \= {\it A model for formal parametric polymorphism: a per interpretation of}\\ \> {\it system $\cal R$}, {R.~Bellucci, M.~Abadi, P.L.~Curien}\\ 4.00 \Paper{Expanding extensional polymorphism} {R.~Di Cosmo, A.~Piperno}\\ {\bf Discussion}\\ 4.30 Open Problem Session, H. Barendregt\\ \end{tabbing} \begin{tabbing} \\ {\bf WEDNESDAY}\\ Morning Session Chaired by: J.~Smith\\ {\bf Machine Assisted Reasoning I}\\ 9.00 \Paper{A verified typechecker} {R.~Pollack}\\ 9.30 \Paper{Higher-order abstract syntax in Coq} {J.~Despeyroux, A.~Felty, A.~Hirschowitz}\\ 10.00 Coffee\\ {\bf Type Theory II}\\ 10.30 \Paper{Using subtyping in program optimization} {S.~Berardi, L.~Boerio}\\ 11.00 \Paper{A simple model for quotient types} {M.~Hofmann}\\ 11.30 \Paper{$\lambda$-calculus, combinators and comprehension systems} {G.~Dowek}\\ \\ 12.00 Lunch\\ \\ \end{tabbing}\newpage \begin{tabbing} Afternoon Session Chaired by: R.~Hindley\\ {\bf Machine Assisted Reasoning II}\\ 2.00 \Paper{Extracting text from proof} {Y.~Coscoy, G.~Kahn, L.~Thery}\\ 2.30 \= {\it Termination proof of term rewriting system with the multiset path ordering and}\\ \> {\it derivation length. A complete development in the Calculus of Constructions},\\ \> {F.~Leclerc}\\ 3.00 Tea\\ {\bf Decision Problems}\\ 3.30 \Paper{Third-order matching in the presence of type constructors} {J.~Springintveld}\\ 4.00 \Paper{On equivalence classes of interpolation equations} {V.~Padovani}\\ 4.30 \Paper{Decidable properties of intersection type systems} {T.~Kurata, M.~Takahashi}\\ \end{tabbing} \end{document} id AA07925; Wed, 23 Nov 1994 22:36:34 -0400 Date: Wed, 23 Nov 1994 22:27:12 -0400 (AST) Subject: pssl in Aarhus, second announcement ---------- Forwarded message ---------- Date: Tue, 22 Nov 1994 14:28:55 +0100 From: Jaap van Oosten The 56th Peripatetic Seminar on Sheaves and Logic will be held in Aarhus, in the weekend of 3-4 December, 1994. Should people still wish to register and avail themselves of relatively cheap accomodation (around 25 British Pounds per night), it is imperative that I receive their registrations before MONDAY November 28, at noon. Hoping to see you in Aarhus, Jaap van Oosten id AA09826; Thu, 24 Nov 1994 01:28:36 -0400 Date: Wed, 23 Nov 1994 22:30:19 -0400 (AST) Subject: 11th ADT Workshop and 8th General Compass Meeting (ASCII & Latex) Date: Wed, 23 Nov 1994 10:29:59 +0100 From: Magne.Haveraaen@ii.uib.no %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%ASCII%%%%%%%%%%%%%%%%%%%%%%%%% 11th ADT Workshop and 8th General Compass Meeting September 19 1995 -- September 23 1995 Call for Participation Workshop on Specification of Abstract Data Types and ESPRIT Compass Meeting --------------------------------------------------------------------------- The two joint events will take place at Holmenkollen in Oslo. The workshop starts just after lunch-time Tuesday September 19, and lasts till Saturday evening September 23. Before the workshop a meeting of the IFIP WG 14.3 (Foundations of Systems Specifications) will be held at the same place starting just after lunch-time Monday September 18. The workshop will provide an opportunity to meet colleagues, to present recent and ongoing work and to discuss new ideas and future trends. The workshop is organized by Olaf Owe and Ole-Johan Dahl from the University of Oslo, and Magne Haveraaen from the University of Bergen. The topics of the workshop include, but are not limited to: - algebraic specifications; - other approaches to formal specification; - specification languages and methods; - term rewriting and proof systems; - specification development systems (concepts, tools, etc.). It is planned to have a small number of invited talks. The proceedings, consisting of a selection of the presented talks through the usual referee process, will be published after the workshop, probably in the Lecture Notes series of the Springer-Verlag (see e.g. the Recent Trends in Data Type Specifications series, n. 332, 534, 655, 785, ...). Please note: as there is a limited number of slots for talks, REGISTER NOW! We will accept speakers essentially in the order of arrival date of their registrations (a corrective mechanism is organized in order to guarantee visibility to every site). So if you plan to have a talk please let us know as soon as possible (communication via e-mail or WWW is suggested). Location -------- The workshop will be held at the Soria Moria hotel at Holmenkollen in Oslo. Even though the site is barely 12 km from downtown and 14 km from the airport, the area has a hilly flavour, surrounded by quiet woods, an excellent terrain for walking. The hotel itself is modern with excellent conference facilities, including swimming pool and sauna. Accommodation ------------- According to the tradition, the workshop is planned on a residential base, so participants are required to stay at the Soria Moria hotel. Normal arrival is expected Tuesday September 19 after lunch, and departure on Sunday September 24 after breakfast, with the possibility of extending the stay in both directions. Participants to the IFIP WG 14.3 meeting are expected to arrive Monday September 18 after lunch. We have reserved a number of rooms, both single and double, and expect to be able to accommodate everybody registering BEFORE JUNE 15. We will try to accommodate people registering by July 31, depending on room availability. Deadline for registration is the 15th of June '95 Please note: the single rooms will be assigned essentially following a FIFO principle; thus if you want a single room, book it now. Prices We have an agreement with the hotel for a special price for full board during the workshop. For a single room this amounts to 880 NOK per day, and to 620 NOK per day per person in a double room. For the whole workshop the prices in Norwegian Crowns amount to: ! WADT/COMPASS (Tue-Sun) ! WG14.3/WADT/COMPASS (Mon-Sun) -----------------+-------------------------+------------------------------ single room ! 4400 NOK (ca. 530 ECU) ! 5280 NOK (ca. 640 EQU) double room, p.p.! 3100 NOK (ca. 375 EQU) ! 3720 NOK (ca. 450 ECU) -----------------+-------------------------+------------------------------ Note that the prices in ECU are obtained at the current rate (which could be different next September). There is a small chance that the boarding prices may be influenced by changes in the Norwegian taxation system. Such changes, if any, will be decided before Christmas. Registration fee ---------------- As usual a reasonable fee will be required at the registration desk, to cover expenses like proceedings publication, social events and so on. The precise amount has still to be established, depending on the real costs and the funds that can be raised to cover them. Travel Information ------------------ The Soria Moria hotel is easily reachable by bus and taxi from downtown Oslo or directly from the Fornebu Airport in Oslo. The dates for the event have been chosen so that participants can make use of reduced airfares (PEX, APEX). Other information ----------------- More organizational details will follow, and registered participants will be kept informed. Updated information will also be available on the World-Wide Web (WWW) at URL: http://www.ifi.uio.no/~adt95/ AS THERE IS A LIMITED NUMBER OF PLACES AVAILABLE FOR THE WORKSHOP, REGISTER EARLY! We will accept participants in the order of date of arrival of the enclosed registration form Please return the registration form (by e-mail or surface mail) to the following address. ADT'95 Organization Institutt for informatikk e-mail: adt95@ifi.uio.no Postboks 1080 Blindern phone: +47 22 85 24 10 0316 OSLO fax: +47 22 85 24 01 Norway WWW: http://www.ifi.uio.no/~adt95/ ------------------------------------------------------------------------ 11th ADT Workshop and 8th General Compass Meeting Registration form One form for each participant, please! Family Name ........................................................ Christian Name ........................................................ Institution ........................................................ Mailing address ........................................................ ........................................................ ........................................................ ........................................................ ........................................................ E-mail ........................................................ Fax ........................................................ Telephone ........................................................ I will attend to the workshop ... yes ... no I intend to give a talk ... yes ... no If yes, provisional title .............................................. ........................................................ ........................................................ I prefer ... single room ... double room I would like to share the room with ................................ Special meal requirements (please specify): ............................ I will arrive .......................... I will depart .......................... I am a member of IFIP WG 14.3 ... yes ... no Name of accompanying non-participants .................................. for which I need ...... additional single rooms and ...... additional double rooms Signature ............................................................. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%LATEX%%%%%%%%%%%%%%%%%%%%%%%%% \documentstyle{article} \topmargin - 21mm \oddsidemargin -11mm \evensidemargin -11mm \textheight 256mm \textwidth 180mm \renewcommand{\arraystretch}{1.5} \catcode`\<=\active\global\chardef~126 %\newcommand{\printtilde}{\verb+~+} \pagestyle{empty} \title{{\LARGE\bf 11th ADT Workshop and 8th General Compass Meeting}} \author{{\Large\bf September 19 1995 -- September 23 1995}} \date{{\large\bf Call for Participation}} \begin{document} \maketitle \thispagestyle{empty} \subsection*{Workshop on specification of Abstract Data Types and ESPRIT Compass Meeting} The two joint events will take place at Holmenkollen in Oslo. The workshop starts just after lunch-time Tuesday September 19, and lasts till Saturday evening September 23. Before the workshop a meeting of the IFIP WG 14.3 (Foundations of Systems Specifications) will be held at the same place starting just after lunch-time Monday September 18. \\ The workshop will provide an opportunity to meet colleagues, to present recent and ongoing work and to discuss new ideas and future trends. The workshop is organized by Olaf Owe and Ole-Johan Dahl from the University of Oslo, and Magne Haveraaen from the University of Bergen. The topics of the workshop include, but are not limited to: \begin{itemize} \item algebraic specifications; \item other approaches to formal specification; \item specification languages and methods; \item term rewriting and proof systems; \item specification development systems (concepts, tools, etc.). \end{itemize} It is planned to have a small number of invited talks. The proceedings, consisting of a selection of the presented talks through the usual referee process, will be published after the workshop, probably in the Lecture Notes series of the Springer-Verlag (see e.g.\ the Recent Trends in Data Type Specifications series, n. 332, 534, 655, 785, \ldots). \medskip \noindent{\bf Please note:} as there is a limited number of slots for talks, {\large\em register now!} We will accept speakers essentially in the order of arrival date of their registrations (a corrective mechanism is organized in order to guarantee visibility to every site). So if you plan to have a talk please let us know as soon as possible (communication via e-mail or WWW is suggested). \subsection*{Location} The workshop will be held at the Soria Moria hotel at Holmenkollen in Oslo. Even though the site is barely 12 km from downtown and 14 km from the airport, the area has a hilly flavour, surrounded by quiet woods, an excellent terrain for walking. The hotel itself is modern with excellent conference facilities, including swimming pool and sauna. \subsection*{Accommodation} According to the tradition, the workshop is planned on a residential base, so participants are required to stay at the Soria Moria hotel. Normal arrival is expected Tuesday September 19 after lunch, and departure on Sunday September 24 after breakfast, with the possibility of extending the stay in both directions. Participants to the IFIP WG 14.3 meeting are expected to arrive Monday September 18 after lunch. We have reserved a number of rooms, both single and double, and expect to be able to accommodate everybody registering {\bf before June 15}. We will try to accommodate people registering by July 31, depending on room availability. \begin{center} \large\bf \fbox{Deadline for registration is the 15th of June '95} \end{center} \medskip \noindent{\bf Please note:} the single rooms will be assigned essentially following a {\tt FIFO} principle; thus if you want a single room, {\em book it now}. \subsubsection*{Prices} We have an agreement with the hotel for a special price for full board during the workshop. For a single room this amounts to 880 NOK per day, and to 620 NOK per day per person in a double room. \noindent For the whole workshop the prices in Norwegian Crowns amount to: \smallskip \begin{center} \begin{tabular}{|l|c|c|}\hline & Just WADT/COMPASS (Tue-Sun) & IFIP WG 14.3 \& WADT/COMPASS (Mon-Sun) \\ \hline single room & 4400 NOK ($\approx$ 530 ECU) & 5280 NOK ($\approx$ 640 EQU) \\ \hline double room, p.p. & 3100 NOK ($\approx$ 375 EQU) & 3720 NOK ($\approx$ 450 ECU) \\ \hline \end{tabular} \end{center} \smallskip Note that the prices in ECU are obtained at the current rate (which could be different next September). There is a small chance that the boarding prices may be influenced by changes in the Norwegian taxation system. Such changes, if any, will be decided before Christmas. \medskip \subsection*{Registration fee} As usual a reasonable fee will be required at the registration desk, to cover expenses like proceedings publication, social events and so on. The precise amount has still to be established, depending on the real costs and the funds that can be raised to cover them. \subsection*{Travel Information} The Soria Moria hotel is easily reachable by bus and taxi from downtown Oslo or directly from the Fornebu Airport in Oslo. The dates for the event have been chosen so that participants can make use of reduced airfares (PEX, APEX). \subsection*{Other information} More organizational details will follow, and registered participants will be kept informed. Updated information will also be available on the World-Wide Web (WWW) at URL: \begin{center} http://www.ifi.uio.no/~adt95/ \end{center} \vspace{0.8cm} \noindent{\Large As there is a limited number of places available for the workshop, register early! \ \ \ \ \ \ \noindent We will accept participants in the order of date of arrival of the enclosed registration form \bigskip \begin{center} REGISTER NOW! \end{center} } \vspace{0.8cm} \noindent Please return the registration form (by e-mail or surface mail) to the following address. \begin{center} \begin{tabular}{lcll} ADT'95 Organization &\makebox[3cm]{}& \\ Institutt for informatikk &&e-mail: &adt95@ifi.uio.no \\ Postboks 1080 Blindern &&phone: &+47 22 85 24 10 \\ 0316 OSLO &&fax: &+47 22 85 24 01 \\ Norway &&WWW: &http://www.ifi.uio.no/~adt95/ \end{tabular} \end{center} \begin{center} \pagebreak {\Large\bf 11th ADT Workshop and 8th General Compass Meeting} \smallskip {\Large\bf Registration form} {\bf One form for each participant, please!} \end{center} \addtolength{\baselineskip}{0.3cm} \bigskip \noindent \makebox[3cm][l]{Family Name} \ \dotfill\ \\ \makebox[3cm][l]{Christian Name} \ \dotfill\ \\ \makebox[3cm][l]{Institution} \ \dotfill\ \\ \makebox[3cm][l]{Mailing address} \ \dotfill\ \\ \makebox[3cm]{} \ \dotfill\ \\ \makebox[3cm]{} \ \dotfill\ \\ \makebox[3cm]{} \ \dotfill\ \\ E-mail \dotfill\qquad Fax \dotfill\qquad Telephone \dotfill\\ \bigskip \noindent \begin{tabular}{lll} I will attend to the workshop & $\Box$ yes & $\Box$ no\\ I intend to give a talk & $\Box$ yes & $\Box$ no\\ \end{tabular} \hspace{1cm}If yes, provisional title \dotfill\\ \makebox[3cm]{}\dotfill\\ \bigskip \noindent I prefer\hspace{2cm} $\Box$ single room\hspace{2cm}$\Box$ double room\\ \hspace{1cm}I would like to share the room with\ \dotfill\\ \bigskip \noindent Special meal requirements (please specify): \dotfill\\ \bigskip \noindent I will arrive \dotfill\\ I will depart \dotfill\\ I am a member of IFIP WG 14.3 \ \ \ $\Box$ yes \ \ $\Box$ no\\ \bigskip \noindent \begin{tabular}{@{}lll}\multicolumn{3}{@{}l@{}}{\hspace*{\textwidth}}\\[0em] Name of accompanying non-participants &\multicolumn{2}{l@{}}{\dotfill} \\ \multicolumn{1}{r}{for which I need} &\ldots\ldots\ldots& additional single rooms and \\ &\ldots\ldots\ldots& additional double rooms \end{tabular} \vfill \hspace{5cm}Signature \dotfill \end{document} id AA10047; Mon, 28 Nov 1994 15:10:03 -0400 Date: Mon, 28 Nov 1994 15:05:18 -0400 (AST) Subject: 57th PSSL Date: Mon, 28 Nov 1994 09:39:51 UTC+0200 From: damphous@univ-tours.fr %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%%% TEX SOURCE OF THE ANNOUNCEMENT BELOW %%%% %%%% TEX SOURCE OF THE ANNOUNCEMENT BELOW %%%% %%%% PLAIN TEX PLAIN TEX PLAIN TEX %%%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %&tex %A4 \font\BF=cmbx12 scaled\magstep3 \font\RM=cmr12 \font\SC=cmcsc10 scaled\magstep1 \font\SL=cmsl12 \font\TT=cmtt12 \baselineskip=16pt \narrower %%%%%%%%%%%% \RM $$\hbox{\BF 57th PERIPATETIC SEMINAR}$$ $$\hbox{\BF ON SHEAVES AND LOGIC}$$ \vskip1.6cm \setbox25=\hbox{Dear Colleagues,}\dimen25=\wd25 \noindent\box25\par\medbreak \noindent\kern\dimen25% This is the announcement of % $$\hbox{\SC THE 57th PERIPATETIC SEMINAR ON SHEAVES AND LOGIC}$$ % This PSSL is to be held in Tours on the 18-19th of february. As usual, talks on topics in logic, category theory and related areas in mathematics and computer science are welcome. Please publicize this meeting amongst your colleagues. At the time of the meeting, {\SC Jiri Rosicky\/} will be a guest at the university {\SL Fran\c cois Rabelais\/}. The meeting will be supported by the university for a fixed amount (not known yet), so that what the fees are to be is not even known by the organizer. At this time of the academic year, housing in the halls of residence is impossible. However, the {\SL Centre R\'egional des Oeuvres Universitaires\/}, has now a splendid {\SL petit h\^otel particulier\/}, (this is the modest local name for private small ch\^ateaux that rich families owned along the Loire river) where we will have the 57th PSSL. It has 33 bedrooms, lecture rooms, a nice and huge garden for mathematical meditation\dots\ Meals will be served on the site. The cost is 210FF per night with breakfast, plus 85FF per meal. The place is rated ***; the cost is however inferior to a plain **-hotel. The fees will be equal to $$\hbox{(total cost - money from the university)/(the number of participants)}.$$ If there is a need for more than 33 bedrooms, arrangements will be made for a hotel. So registering as early as possible (if you intend to come) is going to make the organisation easier. As usual, participants will arrive on friday night or on saturday morning. Lectures will start (probably) at 9.30 on staurday and will finish on sunday morning at noon. It will be possible to have diner there on friday and lunch on sunday. I will send all registered mathematicians complete details on the location of {\SL La croix montoire\/}, the name of this ``petit h\^otel particulier''. It is in Tours on the north shore of the Loire river, and can be reached by urban busses from the train station. \vfill\eject $$\hbox{\SC Please return as soon as possible}$$ $$\hbox{e-mail: {\TT damphous@univ-tours.fr\/}}$$ $$\hbox{$\matrix{\hbox{\SL Pierre Damphousse}\hfill\cr \hbox{\SL D\'epartement de Math\'ematiques}\hfill\cr \hbox{\SL Facult\'e des Sciences}\hfill\cr \hbox{\SL Parc de Grandmont}\hfill\cr \hbox{\SL Tours 37200, FRANCE}\hfill\cr}$}$$ \vskip1.5cm \noindent I would like to attend the 57th PSSL:\par\smallbreak Name:\par\smallbreak Return Address:\par\smallbreak \vskip3cm email:\par \bigbreak \noindent I wish to give a talk entitled:\par\smallbreak of 20/30/45 minutes (specify):\par \bigbreak \noindent I wish to book accomodation from ..................... to ................;\par\smallbreak I will have diner on friday night (not included in the fees) (Yes/No):\par\smallbreak I will have lunch on sunday (not included in the fees) (Yes/No):\par\smallbreak % \bye