Subject:     ? trees
Date: Mon, 6 May 91 15:16:34 EDT
From: barr@triples.Math.McGill.CA (Michael Barr)

Call a rooted tree supercalifragilistic if no node has isomorphic
daughters.  There must be a standard word for this; does anyone know
what it is?

A related question.  Let T denote the set of binary rooted trees.  There
is an idempotent retraction that identifies isomorphic sibs and then
repeats this process until you produce a supercalifragilistic tree.
This retract is compatible with the morphism T --> 1 + T^2/2! (that
means the symmetric square or set of one and two element subsets) that
takes a bare root to 1 and a proper tree to its set of daughters.  Does
anyone know if there are any further retracts that are compatible with
that morphism?

Michael

Subject:     re supercalifragilistic trees
From:       Paul Taylor <pt@doc.ic.ac.uk>
Date:       Wed, 8 May 91 11:09:58 BST

of course there's a standard word - from set theory - extensional!

Subject: Trakhtenbrot Symposium Program, June 10-12, Tel-Aviv

                 ADVANCE PROGRAM
            An International Symposium
                    on
               Theoretical Computer Science

                   in honor of
              BORIS A. TRAKHTENBROT
        on the occasion of his Retirement and Seventieth Birthday

                   sponsored by
    The Moise & Frida Eskenasy Institute of Computer Sciences
          TEL AVIV UNIVERSITY, JUNE 10-12, 1991

                  MONDAY June 10
9:00 REGISTRATION
9:30 OPENING SESSION (Schreiber Bldg., Ramneceanu Hall)
       Amiram Yehudai, Tel-Aviv U., Organizing Chair
       Dan Amir, Vice Rector, Tel-Aviv University
       David Horn, Dean, Raymond and Beverly
              Sackler Faculty of Exact Sciences
       Albert R. Meyer, MIT, Symposium Chair
10:00 J. Barzdins (U. Latvia)
       Inductive synthesis: old and new approaches
10:35 Break
11:05 Eli Shamir (Hebrew U.)
       PAC learning of fuzzy concept classes by quantizing
       the underlying domain
11:40 Michail A. Taitslin (Tver' U., USSR)
       Datalog and expert systems
12:15 LUNCH break
14:00 Arnon Avron (Tel-Aviv U.)
       Problems of decidability and safety in databases
14:35 Jean-Jacques Levy (INRIA, France)
       Explicit substitutions and Pascal compiling schemes
15:10 Break
15:40 Robert Constable (Cornell U. and Weizmann Inst.)
       Constructive type theory as a foundation for computer science
16:15 Gordon D. Plotkin (Edinburgh U.)
       Resumption semantics for dataflow nets
16:50 End of session
17:00-18:30 RECEPTION (in front of Schreiber Bldg.)

                 TUESDAY June 11
9:00  REGISTRATION
9:30  B.A. (Boaz) Trakhtenbrot (Tel-Aviv U.)
       To be announced
10:20 Break
10:40 Alex Rabinovich (IBM Watson, USA)
       The consequence relation of process logic
10:15 Albert R. Meyer (MIT)
       Systems of concurrent automata
11:50 Vaughan Pratt (Stanford U.)
       Must schedule-automaton duality entail conflict persistence?
12:25 LUNCH break
14:15 Amir Pnueli (Weizmann Inst.)
       Fair completeness without ordinals
14:50 Wolfgang Reisig (TU Munich)
       Concurrent temporal logic
15:25 Break
15:55 Rob van Glabbeek (Stanford U.)
       Bisimulation semantics for higher-dimensional automata
16:30 Manfred Broy (TU Munich)
       A functional calculus for nondeterministic interactive systems
17:05 Samson Abramsky (Imperial College, London)
       Proofs as processes
17:40 End of session

                WEDNESDAY June 12
9:00  REGISTRATION
9:30  Rusins Freivalds (U. Latvia)
       Advantages and limitations on advantages of probabilistic
       machines
10:05 Leonid Levin (Boston U.)
       Probability in computing
10:40 Break
11:10 Klaus Wagner (U. Wuerzburg, Germany)
       Complexity classes defined by the local behaviour of
       nondeterministic machines
11:45 Zvi Galil (Tel-Aviv U. and Columbia U.)
       Parallel string matching, upper and lower bounds
12:20 LUNCH break
14:15 Nachum Dershowitz (U. Illinois)
       Infinite rewriting
14:50 Val Breazu-Tannen (U. Pennsylvania)
       Law-abiding constructors
15:25 Break
15:55 V. Yu. Sazonov (Program Sys. Inst., Pereslavl-Zalessky, USSR)
       Some dependence-independence, conservativity and
       expressibility results on weak theories without exponentiation
16:30 Yuri Gurevich (U. Michigan)
       Evolving algebras
17:05 End of Symposium
20:00 BANQUET

The public is invited to attend the lectures and reception without charge.
A limited number of banquet tickets may be purchased at registration.

Lectures will be 30 minutes long plus 5 minutes for questions and will be
held in the Wladimir Schreiber Institute of Mathematics, Room 006,
Tel-Aviv University, Ramat Aviv (by the Diaspora Museum).  Parking through
Gate 1.  There will be a post-symposium excursion on Thursday, June 13.

SYMPOSIUM CHAIR: Albert R. Meyer (MIT)
ORGANIZING COMMITTEE: Zvi Galil (Tel-Aviv U.), Albert R. Meyer (MIT),
Amir Pnueli (Weizmann Inst.), Amiram Yehudai (Tel-Aviv U.)

Direct inquiries to the ORGANIZING CHAIR:
   Prof. Amiram Yehudai
   Computer Science Department
   Tel-Aviv University
   Tel-Aviv, Israel 69978
   Phone: +972-3-5450037 (office)
      +972-3-5450040 (messages)
      +972-3-6423307 (home)
   FAX:   +972-3-6422378
   TELEX: 342171 VERSY IL
   EMAIL: amiram@taurus.bitnet, amiram@math.tau.ac.il

Subject:     CT91 Schedule
Date: Mon, 13 May 91 08:54:20 EDT
From: fox@triples.Math.McGill.CA (Thomas F. Fox)


      PRELIMINARY SCHEDULE OF "CATEGORY THEORY 1991"

                  June 23-30, 1991

            McGill University, Montreal



Sunday, June 23

  1:00-6:00 Registration in Bronfman Bldg.
  8:00 (PM) Reception in Thompson House

Monday, June 24

  8:30 Registration in Bronfman Bldg
  9:30 Abramsky, Samson: TBA
  11:00 Carboni, Aurelio: Recent developments on affine and Mal'cev
       categories

A:1:30 Chen, Hong (Andy): Categorical programming languages
  2:05 Bonacina, M. Paola: A category theory approach to completion-based
       theorem proving strategies
  2:40 Mulry, Philip S.: Strong monads, algebras and fixed points
  3:40 Blute, Richard: Linear logic, coherence theorems and dinaturality
  4:15 Rosebrugh, Robert: Relational databases and indexed categories

B:1:30 Diers, Yves: A new universal construction in the category of
       commutative rings
  2:05 Dula, Giora: A functor from groupoids to rings
  2:40 Borceux, Francis: Morita theory for algebraic theories
  3:40 Bourn, Dominique: Normalization equivalence, kernel equivalence
       and affine categories
  4:15 Pedicchio, M.C.: Mal'cev categories

Tuesday June 25

  9:00 Lamarche, Francois: It is time to generalize Grothendieck toposes
  10:30 Jardine, John F.: Homotopy theory and coherence

A:1:00 Otto, James: Higher order initial models I: from fl to lcc
  1:35 Freyd, Peter: Formal Methods
  2:10 Rumbos, Beatriz: Transition probability and non-commutativity of
       states
  3:10 Cockett, Robin: The fundamental theorem of data structures for a
       locos

B:1:00 Hardie, Keith: Comparing the classical and coherent homotopy sets
       under A and over B
  1:35 Steiner, Richard: Nerves and tensor products of multiple
       categories
  2:10 Moerdijk, Ieke: Diaconescu's theorem and classifying spaces
  3:10 Tierney, Myles: TBA
  3:45 Joyal, Andre: TBA
  4:20 Bunge, Marta: Indexed categories and distributions on toposes

Wednesday June 26

  9:00 Pitts, Andrew: Toposes and Heyting algebras
  10:30 Isbell, John: Descriptive local theory

A:1:00 Lozanov, Rumen: Kleene's theorem for categories
  1:35 Benabou, Jean: Some aspects of definability
  2:10 Reyes, Gonzalo: TBA
  3:10 Picado, Jorge: On two extensions of Dickson's torsion theory

B:1:00 Janelidze, Georg: Higher dimensional galois theory: the first
       version
  1:35 Gordon, Robert: Categories enriched over closed bicategories
  2:10 Kelly, Gregory M.: Closed and cartesian closed bicategories
  3:10 MacDonald, John: Soft adjunctions and 2-level algebras
  3:45 Datuashvili, Tamaz: On the category of internal categories in the
       category of groups with operations

  7:00 BANQUET

Thursday June 27

  9:00 Trnkova, Vera: Functorial selection of morphisms
  10:30 Wood, Richard: Adjoint quadra-modules

  EXCURSION

Friday June 28

  9:00 Street, Ross: Diagrams for tensor categories with duality
  10:30 Pelletier, Joan: Quantales of linear relations

A:1:00 Niefield, Susan: Quantales and Boolean quotients
  1:35 Rosenthal, Kimmo: Quantaloidal nuclei - the syntactic congruence
       and tree automata
  2:10 Roman, Leopoldo: Quantum logic and Girard quantales
  3:10 Flagg, Robert: Quantales and continuity spaces
  3:45 Zangurashvili, Dali: Some categorical algebraic properties of
       functors with values in categories without products
  4:20 Squire, Richard: Maximally ordered objects in a topos

B:1:00 Pachuashvili, Beso: Cohomologies of Steenrod algebra with
       coefficients in cohomologies of topological space
  1:35 Grandis, Marco: Homological algebra in homological categories
  2:10 Pachkoria, Alex: Homological algebra in the category of
       commutative monoids
  3:10 MacLane, Saunders: Monoidal categories, coherence and quantum
       fields
  3:45 Majid, Shahn: Braided groups and duals of monoidal categories
  4:20 Lyubashenko, Vladimir: Rational modular tensor categories and CFT

Saturday June 29

  9:00 Moggi, Eugenio: The mathematical structure of programming
       languages
  10:30 Meloni, Gian Carlo: Topological and relational semantics for
        predicative classical modalities

A:1:00 Richter, Gunther:  Categorical descriptions of categories of
       Hausdorff spaces
  1:35 Ageron, Pierre: Cartesian closed categories of accessible
       categories
  2:10 Hu, Hongde: Duality for some accessible categories
  3:10 Nel, Louis D.: Existence theorems in analysis via categorical
       methods
  3:45 Koslowski, Juergen: Hereditary and modal closure operators, hulls
       and cores

B:1:00 Sobral, Manuela: Remarks on the change-of-base functor
  1:35 Pavlovic, Dusko: Functional comprehension and relative toposes
  2:10 Sun, Shu-Hao: Sheaf representations of universal algebras
  3:10 Tavakoli, Javad: Omega-valued internal sheaves in a topos
  3:45 Jarzembski, Grzegorz: Topological properties of free spectra of
       categories of mixed structures
  4:20 Kock, Anders: Local equivalence relations and their sheaves

__________________________________________________________

THE FINAL SCHEDULE WILL BE DETERMINED ON MONDAY JUNE 23.
THE FOLLOWING TALKS ARE TENTATIVE:

Bauer, F. W.: A strong shape category
Betti, Renato: Algebraic categories over topoi
Brown, Ronnie: Crossed Differential Graded Algebras
Duskin, Jack: TBA
Guitart, Rene: Classe caracteristiques des esquisses fibrees
Hoehnke, Hans-Juergen: Loop categories
Nassopoulos, George F.: An internal characterization of the base
     category V.
Obtulowicz, Adam: Higher level families of structures & their
     applications
Popescu, Nicolae: Valuations on K(X)
Pumpluen, D.: Convex spaces
Taylor, Paul: TBA
Topencharov, Vladimir: Diagonal categories in double and n-tuple
     categories
Trimble, Todd: TBA
Vermeulen, Japie: Perfect descent
Zawadowski, Marek: Descent techniques in categorical doctrines

ALL TALKS WILL BE IN THE BRONFMAN BUILDING OF MCGILL UNIVERSITY
AT 1001 SHERBROOKE W., MONTREAL

THE RECEPTION SUNDAY EVENING WILL BE HELD IN THOMPSON HOUSE AT
3650 MCTAVISH ST.

FURTHER INFORMATION: mt16@musica.mcgill.ca

Subject:     addresses
Date: Wed, 15 May 91 16:53:22 +10
From: kelly_m@maths.su.oz.au (Max Kelly)

Michael,Bob - has either of you email addresses for Banaschewski &
for Harry Simmons? If not,
how about fax or home telephone? Perhaps your BB, Bob.
Thanks. Max, 15 May.

Date: Fri, 17 May 91 12:37:22 +10
From: kelly_m@maths.su.oz.au (Max Kelly)

Let a category A be locally finitely presentable, and let B be a full
reflective subcategory for which the inclusion B ---> A is FINITARY - that is,
preserves filtered colimits. Is there necessarily in A a set of arrows of the
form k:M ---> N, where M and N are finitely presentable, such that B consists
of the objects ORTHOGONAL to each k, in the sense that an object a of A is in B
if & only if each A(k,a):A(N,a) ---> A(M,a) is invertible? It is easy to see
that it suffices to answer the question when A is a presheaf category P; just
express A as a finitarily reflective subcategory of such a P. It is of course
true that B is locally finitely presentable, & is therefore expressible as the
full subcategory of some presheaf category Q, given by the objects of Q
orthogonal to a set of arrows between locally-presentables; that is not the
point.

Max Kelly, 17 May.

Subject:     Theor. Aspects of Software, Sendai, Japan, 9/24-27/91
Date: Mon, 20 May 91 13:23:34 EDT
Reply-To: tacs91@ito.ecei.tohoku.ac.jp, tacs-request@theory.lcs.mit.edu

           PRELIMINARY PROGRAM and REGISTRATION

               International Conference on
        THEORETICAL ASPECTS OF COMPUTER SOFTWARE (TACS'91)
                           September 24-27, 1991
                     Tohoku University, Sendai, Japan

   Sponsored by Tohoku University, Sendai, in cooperation with the
   Information Processing Society of Japan, the Japan Society for Software
   Science and Technology, the Association for Symbolic Logic, ACM SIGACT and
   the pending cooperation of the IEEETC on Mathematical Foundations of
   Computing and ACM SIGPLAN.

                           CONFERENCE CO-CHAIRS
   Prof. Takayasu Ito                        Prof. Albert R. Meyer
   Department of Information Engineering     MIT Laboratory for Computer Science
   Tohoku University                         545 Technology Square, NE43-315
   Sendai, Japan 980                         Cambridge, MA 02139, USA
   email: tacs91@ito.ecei.tohoku.ac.jp       email:
 tacs-request@theory.lcs.mit.edu
   FAX: 81 22 267 4404                       FAX: (617) 253 3480

                           PROGRAM COMMITTEE
   Robert Constable (Cornell U.)         Masami Hagiya (Kyoto U.)
   Susumu Hayashi (Ryukoku U.)           Takayasu Ito, Co-Chair (Tohoku U.)
   J.-L. Lassez (IBM, Yorktown)          Albert R. Meyer, Co-Chair (MIT)
   Gordon D. Plotkin (Edinburgh U.)      Amir Pnueli (Weizmann Inst.)
   Masahiko Sato (Tohoku U.)             Dana Scott (Carnegie-Mellon U.)


CONFERENCE PROGRAM
               MONDAY 23 SEPTEMBER
             Autumnal Equinox Holiday
15:00-20:00  REGISTRATION at Sendai Tokyu Hotel
18:00-19:30  WELCOME RECEPTION at Sendai Tokyu Hotel

               TUESDAY 24 SEPTEMBER
9:30    OPENING SESSION
     Takayasu Ito, TACS Co-Chair (Tohoku U.)
     Albert R. Meyer, TACS Co-Chair (MIT)
10:00    INVITED TALK 1
    On the completeness of type-checking
     Gordon D. Plotkin (Edinburgh U.)
10:50    BREAK
11:20-12:20  SESSION 1
11:20    Type inference in polymorphic type discipline
     Paola Giannini, Simona Ronchi Della Rocca (U. Torino)
11:50    Monotone recursive definition of predicates and its
    realizability interpretation
     Makoto Tatsuta (Tohoku U.)
12:20    LUNCH
13:30    INVITED TALK 2
    Adding proof objects and inductive definition mechanisms
    to Frege structures
     Masahiko Sato (Tohoku U.)
14:20    BREAK
14:50-15:50  SESSION 2
14:50    From term models to domains
     Wesley Phoa (Cambridge U.)
15:20    An abstract interpretation of ML equality kinds
     Carl A. Gunter (U. Pennsylvania)
     Elsa L. Gunter, David B. MacQueen (AT&T Bell Laboratories)
15:50    BREAK
16:20-17:10  INVITED TALK 3
    Full abstraction and the context lemma
     Albert R. Meyer (MIT Laboratory for Computer Science)
19:00-20:30  RECEPTION at Sendai Tokyu Hotel

              WEDNESDAY 25 SEPTEMBER
9:30-11:00   SESSION 3
9:30    An efficiency preorder for processes
     S. Arun-Kumar (Indian Institute of Technology)
     M. Hennessy (U. Sussex)
10:00    On nets, algebras and modularity
     Alexander Rabinovich (IBM T.J. Watson Research Center)
     Boris A. Trakhtenbrot (MIT and Tel Aviv U.)
10:30    Towards a complete hierarchy of compositional dataflow models
     Bengt Jonsson (Swedish Institute of Computer Science)
     Joost N. Kok (Utrecht U.)
11:00    BREAK
11:30    INVITED TALK 4
    Constructive aspects of classical logics
     Robert L. Constable (Cornell U.)
12:20    LUNCH
13:30    INVITED TALK 5
    Applying formal methods to software development--partially
     Amir Pnueli (Weizmann Institute of Science)
14:20    BREAK
14:50-15:50  SESSION 4
14:50    Proving termination of general Prolog programs
     Krzysztof R. Apt (CWI, Amsterdam)
     Dino Pedreschi (U. Pisa)
15:20    On abstraction and the expressive power of programming languages
     John C. Mitchell (Stanford U.)
15:50    BREAK
16:20-17:10  INVITED TALK 6
    Role of logic programming in the FGCS project
     Kazuhiro Fuchi (ICOT, Tokyo)
19:00-21:00  BANQUET at Sendai Tokyu Hotel
    Banquet Speech by Rod Burstall (Edinburgh U.)

              THURSDAY 26 SEPTEMBER
9:30-11:00   SESSION 5
9:30    Authentication and delegation with smart-cards
     M. Abadi, M. Burrows, C. Kaufman, B. Lampson
     (DEC Systems Research Center, Palo Alto)
10:00    Data flow analysis as model checking
     Bernhard Steffen (RWTH--Aachen)
10:30    On the adequacy of dependence-based representations for
    programs with heaps
     Phil Pfeiffer (U. Wisconsin-Madison)
     Rebecca Parsons Selke (Rice U.)
11:00    BREAK
11:30    INVITED TALK 7
    From programming-by-example to proving-by-example
     Masami Hagiya (Kyoto U.)
12:20    LUNCH
13:30    INVITED TALK 8
    Programming with constraints
     Jean-Louis Lassez (IBM Watson Research Center)
14:20    BREAK
14:50-16:05  SESSION 6
14:50    Polynomial recursion analysis in Pascal like programs
     Dieter Armbruster (U. Stuttgart)
15:05    Complexity of proving program correctness
     Hardi Hungar (U. Oldenburg)
15:20    Some normalization properties of Martin-Lof's type
    theory, and applications
     David Basin (Edinburgh U.)
     Doug Howe (Cornell U.)
15:35    Parametricity of extensionally collapsed term models of
    polymorphism and their categorical properties
     Ryu Hasegawa (Kyoto U.)
15:50    Programs with continuations and linear logic
     Shin-ya Nishizaki (Kyoto U.)
16:05    BREAK
16:35-17:35  SESSION 7
16:35    PI-calculus semantics of object-oriented programming languages
     David Walker (U. Technology, Sydney)
16:50    Wrapper semantics of an object oriented programming
    language with state
     Andreas V. Hense (U. Saarlandes, Saarbrucken)
17:05    Sharing actions and attributes in modal action logic
     Mark Ryan, Jose Fiadeiro, Tom Maibaum (Imperial College, London)
17:20    First order data types and first order logic
     Ralf Treinen (U. Saarlandes, Saarbrucken)
17:35    BREAK WITH SANDWICH
19:00-20:30  EVENING SESSION 8
    Demos and informal presentations

               FRIDAY 27 SEPTEMBER
9:30-11:00   SESSION 9
9:30    Principal type-schemes of BCI-lambda-terms
     Sachio Hirokawa (Kyushu U.)
10:00    Intersection and union types
     F. Barbanera, M. Dezani-Ciancaglini (U. Torino)
10:30    The coherence of languages with intersection types
     John C. Reynolds (Carnegie Mellon U.)
11:00    BREAK
11:30    INVITED TALK 9
    Singleton, union and intersection types in program extraction
     Susumu Hayashi (Ryukoku U.)
12:20    LUNCH BREAK
13:30-14:30  SESSION 10
13:30    Subtyping + extensionality: confluence of beta-eta
    reduction in F_(<=)
     Pierre-Louis Curien (LIENS/CNRS, Paris)
     Giorgio Ghelli (U. Pisa)
14:00    An extension of system F with subtyping
     Luca Cardelli (DEC Systems Research Center, Palo Alto)
     Simone Martini (U. Pisa)
     John C. Mitchell (Stanford U.)
     Andre Scedrov (U. Pennsylvania)
14:30    BREAK
15:00    INVITED TALK 10
    Will logicians be replaced by machines?
     Dana S. Scott (Carnegie-Mellon U.)
15:50-16:00  CLOSING SESSION
     Albert R. Meyer, TACS Co-Chair (MIT)
     Takayasu Ito, TACS Co-Chair (Tohoku U.)

              SATURDAY 28 SEPTEMBER
           Bus Tour to Hiraizumi and Matsushima
9:00    Depart Sendai Tokyu Hotel
    Hiraizumi (Chusonji Temple with Golden Pavilion)
    Lunch
    Matsushima (Famous Views of Pine-covered Islets, Zuiganji Temple)
    Dinner at a Japanese restaurant
20:30    Return Sendai Tokyu Hotel
--------------------------------------------------------------------------

GENERAL INFORMATION

TACS'91 will be held on the campus of Tohoku University, Sendai, Japan.
Lectures will be presented in the Aoba Memorial Building, Faculty of
Engineering located on the Aoba Hill about 3 km west of downtown Sendai.
Receptions and a banquet will be held at the Sendai Tokyu Hotel, located
in downtown Sendai.  A post conference bus tour to Hiraizuki (Chusonji
Temple with its golden pavilion) and Matsushima (famous views of
pine-covered islets and Zuiganji Temple) will take place on September 28.

Sendai is the largest city in the northern part of the Honshu Island of
Japan, with a population of about 900,000.  The city is known in Japan as
the "City of Trees".  It is 350 km north from Tokyo and less than 2 hours
away by the Tohoku Bullet Train (Tohoku Shinkansen).  Sendai is a modern,
safe city with a temperate climate blessed by four distinct, beautiful
seasons.

Conference registration is open to the public.  Reservations for the post
conference bus tour will be limited.  Register and make reservations by
returning the completed form below by email, FAX, or airmail.  There will
also be on-site registration at:
     Sendai Tokyu Hotel, 15:00-20:00, September 23,
     Aoba Memorial Bldg., Tohoku Univ., 9:00-17:00 on September 24-27.

A proceedings, published as a volume in Springer-Verlag's Lecture Notes in
Computer Science, will be given to registrants on arrival.

TRANSPORTATION

Conference participants arriving at the new TOKYO INTERNATIONAL (NARITA)
Airport are advised to take the JR Narita Express train from Narita
Airport to Tokyo Station.  Then take the Yamabiko super express train of
Tohoku Shinkansen (Tohoku Bullet Train) to Sendai from Tokyo. The Yamabiko
runs almost every 30 min. and takes less than 2 hours from Tokyo to
Sendai.  Making reservations at Narita Station for the Yamabiko express is
strongly recommended, since it will be the autumnal tourist season.

NOTE: No flight service is available from Narita Airport to Sendai
Airport, since the train service is superior. The JR Narita Express is a
new service started this March, and Tohoku Shinkansen from Tokyo Station
is a new service starting at the end of this June.  If you are going to
travel in Japan before/after the conference it will be convenient and
economical to get a JR PASS before your departure.  Contact your travel
agent for more information.

Those arriving at OSAKA INTERNATIONAL Airport can fly to Sendai Airport,
and take the Limousine Bus service to Sendai Station.  The bus takes about
45 min. to go from the Airport to Sendai Station.  You can also take the
Tokaido Shinkansen from Osaka to Tokyo Station and change at Tokyo Station
to Tohoku Shinkansen for Sendai.

Three recommended hotels offer special discount rates to TACS'91
participants: the Sendai Tokyu Hotel, the Sendai Washington Hotel II, and
the Sendai Fuji Hotel.  They are 1.2 km west of Sendai Station and about
500 Yen by taxi from the station.  The receptions and banquet will be held
at the Sendai Tokyu Hotel. The other two hotels are located within 5 min.
walk of the Sendai Tokyu.

CLIMATE

The weather in Sendai from the middle of September to the middle of
October is usually delightful--mostly sunny with temperatures ranging from
the low 50's F (10's C) to the low 70's F (20's C).  A light jacket may be
needed in the morning and evening.  Rain, if any, would rarely be heavy.

Date:        Tue, 21 May 91 14:13:34 ADT
Subject:     Constructivity symposium


Announcing a Summer Symposium ...

               CONSTRUCTIVITY IN COMPUTER SCIENCE

                        June 19-22, 1991
                       San Antonio, Texas

                          Sponsored by
                       Trinity University
                   The University of Chicago
               The Association for Symbolic Logic


Top-Down Agenda:

     Wednesday, June 19                          Friday, June 21
       11 AM - 5 PM   Registration                 7 AM - 8 AM   Breakfast
       4 PM           Welcome                      8 AM - noon   Paper Sessions
       4:15 -  6 PM   Paper Session                noon - 1 PM   Lunch
       6:30 PM        Reception and dinner         1 PM - 5 PM   Paper Sessions
                                                   6:30 PM  Reception & Banquet

     Thursday, June 20                           Saturday, June 22
       7 AM - 8 AM    Breakfast                    7 AM - 8 AM   Breakfast
       8 AM - noon    Paper Sessions               8 AM - noon   Paper Sessons
       noon - 1 PM    Lunch                        noon          Closing
       1 PM - 5 PM    Paper Sessions

The following have been accepted for presentation in the final program:

"Extracting Computational Content from Constructive and Classical Proofs,"
   R.L. Constable (Cornell).
"Constructive Topology and Combinatorics,"
   T. Coquand (Chalmers Tekniska Hogskola).
"Development Transformation Based on Higher Order Type Theory,"
   Lu Jianguo & Xu Jiafu (Nanjing).
"Constructivity Issues in Graph Algorithms,"
   M. Langston (Tennessee) & M.R. Fellows (Victoria).
"Kripke Semantics for Dependent Type Theory and Realizability,"
   J. Lipton (Pennsylvania).
"Classic Proofs as Programs: How, What, and Why,"
   C. Murthy (Cornell).
"Computational Logic,"
   M. Napierala (Oregon Graduate Institute of Science and Technology).
"Connecting Formal Semantics to Constructive Intuitions,"
   M.J. O'Donnell (Chicago).
"Reflective Semantics of Constructive Type Theory,"
   S. Smith (Johns Hopkins).
"Axiomatization of Calculus of Constructions,"
   Yong Sun (York).
"A Logical View of Assignments,"
   V. Swarup (Mitre) & U.S. Reddy (Illinois at Urbana-Champaign).
"Are Subsets Necessary in Martin-Lof Type Theory?"
   S. Thompson (Kent at Canterbury).
"Examples of Semicomputable Sets of Real and Complex Numbers,"
   J.V. Tucker (Swansea) & J.I. Zucker (McMaster).
"Some Properties and Applications of the Lawson Topology,"
   S. Yoccoz (Bordeaux).

Three papers will constitute an additional  "Curriculum Session":

"Bringing Mathematics Education into the Algorithmic Age,"
   N. Greenleaf (Columbia).
"The Type Structure of CAT,"
   R.E. Prather & J.P. Myers, Jr. (Trinity).
"A Simple and Powerful Approach for Studying Constructivity, Computability,
   and Complexity,"  K. Weihrauch (Fernuniversitaet).


FEES

     Registration                   $100
     Housing & Meals
       One person (double occ.)     $150 OR
       One person (single occ.)     $180
     Lodging, Sat. night            $ 15

  The symposium is "residential" to promote informal contacts.  For someone
  not residing on-campus, a meal package is available for $45.


FOR ADDITIONAL INFORMATION AND REGISTRATION FORMS, contact

     J. Paul Myers, Jr.
     Department of Computer Science         PHONE:  (512)736-7398
     Trinity University                     E-MAIL (BITNET):
     San Antonio, Texas  78209                      pmyers AT trinity
     USA

-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
J. Paul Myers, Jr.                        Department of Computer Science
Trinity University                                     715 Stadium Drive
San Antonio, Texas 78212                                  (512) 736-7398
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=

Date: Wed, 22 May 91 17:23:43 MET DST
From: curien@FRULM63.BITNET (Pierre-Louis Curien)
Subject: CATEGORY THEORY AND COMPUTER SCIENCE 91

FOURTH BIENNAL CONFERENCE ON

CATEGORY THEORY ANDCOMPUTER SCIENCE   (C.T.C.S . )

3- 6  September 1991

The Fourth of the Biennal Summer  Conferences  on
Category  Theory  and Computer Science will be held in
Paris (France).

The main purpose of these conferences is to link research   in  category

theory with computer science.  The importance of categories in
understanding basic issues in computer science is now well
established. Other structures in logic, algebra and  topology are
also seen as fundamental and the scope of the conference

is  to cover applications of these structures as well.
Proceedings are published in the Springer LNCS series.
Organising and Programe Committee :

Samson Abramsky, Pierre-Louis Curien, Peter Dybjer, Giuseppe Longo,
John Mittchell, David Pitt, Andrew Pitts, Axel Poigne' ,
David Rydeheard, Don Sannella, Eric Wagner.

                Invited speakers

Albert Burroni                  Eugenio Moggi
Thierry Coquand         Ugo Montanari
Peter  Freyd                    Robert  Tennent

Local Arrangements Office
 C.A.I.M.E.N.S   /  E.N.S.
45, rue dUUlm
75230 Paris Cedex 05

Te l  :   (33)   (1 ) 43 29 12 25 ext. 3279
Fax :   (33)    (1)  46 34 05 31
Email : butery@dmi.ens.fr
Person in charge :  Chantal Butery




Sponsorship :  MRT (Ministe` re de  la  recherche et de  la  technologie),
CNRS ( Centre national  de  la  recherche scientifique),
(MEN Minist re de  l'e'ducation nationale ).

Location :  The  conference will take place at :

                FIAP  Jean Monnet               30, rue Cabanis         75014 Pa
                France
                (Me'ro station :  Glacie`re)

Accommodation, breakfast and  self facilities for lunch or

dinner  will be provided by FIAP and  are  included  in the
registration  fees (as well as a conference dinner).

Accommodation :   On the basis of students prices,
the FIAP  arranged  for  CTCS participants  the possibility of
booking double rooms  to be shared or single rooms (in a limited number).
Both  types of rooms are provided  with private
shower, wash-basin, toilets and  telephone.

Other events :  There will be a  conference dinner.
 FIAP can also provide information on  touristic or cultural
activities  in Paris and Paris area.

Accommodation :Please fill and return your registration
form to the Local Arrangements Office (CAIMENS / ENS),
accompanied with a cheque of the corresponding amount in
French Francs payable at CAIMENS.  If you find it easier,
you can also make a bank transfer  to  CAIMENS :

Bank name and address :  Soci e't e'   Ge' ne' rale
37, rue Gay-Lussac, 75005  Paris.
Account  number :  00037266208

with  the reference CTCS, and  making sure  that your name
will  appear clearly.   Acknowledgment  will be dispatched  in  due time.


 C.T.C.S.  -   91    P R O G R A M M E



        Tuesday   (September 3rd)

 9:30  -  10:30  P.  Freyd, invited  talk
10:30  -  11:00 Coffee / Tea Break
11:00  -   11:40        T. Ehrhard & P. Malacaria, Stone  Duality

for Stable Functions
11:40  -   12:20        R. Amadio, Bifinite Domains:  Stable Case

Lunch

14:00  - 15:00  R. Tennent ,  invited talk
15:00  -  1540  A. Edalat & M. Smyth, Categories of Information Systems
15:40  - 16:10  Coffee / Tea Break
16:10 - 16:50   R. Hoofman &  H.Schellinx,  Collapsing Graph
Models by Preorders
16:50 - 17:30   P.  OUHearn, Linear Logic and Interference Control

Wednesday   (September 4th)

 9:30 - 10:30   A. Burroni, Invited talk
10:30 - 11:00   Coffee / Tea Break
11:00  - 11:40  S. Hirokawa, BCK-formulas  Having Unique Proofs
11:40 -  12:20  R. Blute, Proof Nets and  Coherence Theorems

Lunch

Afternoon    free
Conference   Dinner


        Thursday  (September 5th)



9:30   - 10:30  E. Moggi, Invited  talk
10:30 -  11:00  Coffee / Tea Break
11:00  -  11:40 G. Jarzembski, Programs in Partials  Algebras -

a  Categorical   Approach
11:40  - 12:20  B. Jay, Tail Recursion from  Universal  Invariants

Lunch

14:00  -  15:00 T. Coquand, Invited  talk
15:00  -  15:40 D. Pavlovic, Constructions and  Predicates
15:40  -  16:10 Coffee / Tea Break
16:10  -  16:50 B. Jacobs, E.  Moggi  & T.Streicher  Relating
Models of Impredicative Type Theories
16:50  -  17:30 W.  Phoa, Set-theoretic  Polymorphism after Robinson

        Friday  (September 6th)

 9:30  -  10:30 U.  Montanari, Invited  talk
10:30  -  11:00 Coffee / Tea Break
11:00   -  11:40 E. Stark,  Dataflow Networks are Fibrations
11:40  -  12:20 P. Degano,S. Kasangian  &  S.Vigna Applications
of the Calculus of Trees to Process Description Languages

Lunch

END  OF  CONFERENCE

Date:        Fri, 24 May 91 16:57:15 ADT
Subject:     Kan extensions programs

------ kan ver 1.0 -------------------------------------------

     Sean Carmody
     Craig Reilly
     Bob Walters

     16th May 1991
--------------------------------------------------------------

  An implementation of the algorithm developed in 1990 by
Carmody & Walters to compute (finite) left Kan extensions
is now operational (programmed by Reilly and Carmody).
  It is available by anonymous ftp from Sydney University:

                 ftp  maths.su.oz.au

  (NOTE "maths" not "math")

  There are also some sample input files as well as a file
called KAN.info which gives further details of the program
and one called README which describes the sample input files.
If you experiment with the program, we would be very
interested to hear any comments or suggestions (especially
with regards any bugs which you -- hopefully won't -- find).


   Sean Carmody.

   (email: carmody_s@maths.su.oz.au)

--------------------------------------------------------------

Date:        Fri, 24 May 91 17:42:45 ADT
From: fox@triples.Math.McGill.CA (Thomas F. Fox)
Subject: CT91 Directions



CATEGORY THEORY 1991

MORE INFORMATION FOR PARTICIPANTS

June 23 - 30, 1991
McGill University, Montreal

TALKS: Sixty-four talks have been scheduled, including twelve one hour talks by
 invited speakers and fifty-five half hour talks in parallel sessions.  The
 first talk will be Monday, June 23 at 9:30.  The last
talk is scheduled for Saturday, June 29 at 4:20.  All talks will be in
the Bronfman Building of McGill University at 1001 Sherbrooke St. West.

REGISTRATION:  A registration desk will be set up in the Bronfman
Building at 1001 Sherbrooke Street West on Sunday, June 23 from 1:00 to
6:00.  You may also register at the reception Sunday evening or before
the first talk on Monday.

RECEPTION:  On Sunday evening there will be a reception in Thompson House
(the Graduate Student Centre) at 3650 McTavish from 8:00 to 11:00.
Thompson House will be open to participants and their guests throughout
the week as a relaxing meeting place.  (If you are a member of a North
American faculty club, the facilities of the McGill Faculty Club are also
available.  Bring your membership card.)

BANQUET:  There will be a banquet for participants on Wednesday evening.
By June 20 we must know the number of people attending the banquet, so if
you plan pay your registration fee only upon arrival, please confirm
your participation by June 20.  Guests (accompanying persons) are welcome
at a cost of $35 per person.

EXCURSIONS:  On Thursday afternoon there will be two excursions available
to participants and their guests - a picnic/walk in a nature preserve at
Mt. St. Hilaire outside of the city, or a lunch and walking tour of Old
Montreal.  We will ask you sign up for one or the other at registration.
There will be a small charge for accompanying persons.

DIRECTIONS FROM AIRPORTS:  Montreal has two airports, the North American
airport at Dorval, and the International airport at Mirabel.
From DORVAL:  A taxi to McGill will cost $20.  There is an airport bus
(cost $8.50) at X:15 and X:45 which stops at the Queen Elizabeth Hotel,
five blocks from McGill, ten blocks from the dorms.  A taxi from the
Queen E to McGill costs $3.50.
From MIRABEL:  A taxi to McGill will cost $50.  There is an airport bus
which costs $11.75, and goes to the Queen Elizabeth Hotel (see above).
The bus leaves Mirabel on the hour 24 hours a day, and on the half hour
from 12:30 to 19:30.

BY TRAIN:  Central Station is next door to the Queen Elizabeth Hotel,
five blocks south of McGill.  Take the escalator to Blvd. Rene Levesque
and hail a cab or walk north, towards the mountain.

BY CAR FROM THE US:  From the US, cross the Champlain Bridge.
Immediately after the toll booth exit to the right.  Follow the signs
that say "Centre Ville" and you will find yourself on University Street
going north.

DORMS:  Guests staying in the McGill Dorms may go directly to Bishop
Mountain Hall, located at 3935 University St (the northern end of
University street).  A night guard will be on duty to welcome late
arrivals.  There is (limited) parking in the dorm complex.


We have maps and tourist information available upon request.  If you
have any questions or need further information, please contact us at
the address given below.


CATEGORY THEORY 1991
Math Dept, McGill University
805 Sherbrooke St W
Montreal, Quebec
CANADA  H3A 2K6

Email:  mt16@musica.mcgill.ca
Fax:    (1-514) 398-3899
Tel:    (1-514) 398-3806

Date: Mon, 27 May 91 15:47:47 EDT
From: barr@triples.Math.McGill.CA (Michael Barr)
Subject: email address for Hugo Volger?

Does anyone have?
Michael
