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FAQ: Prolog Resource Guide 1/2 [Monthly posting]

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Archive-name: prolog/resource-guide/part1
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;;; ****************************************************************
;;; Prolog Resource Guide ******************************************
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;;; prg_1.faq

This post contains the Prolog Resource Guide.

Contributions, corrections, suggestions, and comments should be sent
to Mark Kantrowitz <>. 

This guide lists a variety of resources for the Prolog community,
including books, magazines, ftp archives, and products. It is posted
on the 13th of every month to the newsgroups comp.lang.prolog and
comp.object.logic. The PRG is also posted to the newsgroups
news.answers and comp.answers where they should be available at any
time (ask your local news manager).

*** Copyright:

Copyright (c) 1992-94 by Mark Kantrowitz. All rights reserved.

This FAQ may be freely redistributed in its entirety without
modification provided that this copyright notice is not removed.  It
may not be sold for profit or incorporated in commercial documents
(e.g., published for sale on CD-ROM, floppy disks, books, magazines,
or other print form) without the prior written permission of the
copyright holder.  Permission is expressly granted for this document
to be made available for file transfer from installations offering
unrestricted anonymous file transfer on the Internet.

If this FAQ is reproduced in offline media (e.g., CD-ROM, print form,
etc.), a complimentary copy should be sent to Mark Kantrowitz, School
of Computer Science, Carnegie Mellon University, 5000 Forbes Avenue,
Pittsburgh, PA 15213-3891 USA.

This article is provided AS IS without any express or implied warranty.

*** Recent Changes:

;;; 1.30:
;;;  7-AUG-95 mk    Updated Amzi! entry in part 2.
;;; 1.31:
;;; 29-AUG-95 mk    Added ORISA Prolog entry to part 2.
;;; 29-AUG-95 mk    Added [1-19] about ISO Prolog Standard
;;; 30-AUG-95 mk    Updated entry for LPA Prolog in part 2.
;;; 12-SEP-95 mk    Several changes to [1-1], [1-3], [1-13], [1-15] and part 2
;;;                 (ALS Prolog and CLP(RI)) by Ken Bowen.
;;; 1.32:
;;; 18-SEP-95 mk    Updated Prolog by BIM and IBM Prolog entries.
;;; 1.33:
;;; 18-OCT-95 mk    Added entry on Mercury to [2-7].
;;;  9-NOV-95 mk    Updated ALP info - Logic Programming Newsletter and [1-4].
;;; 19-MAR-96 mk    Added note about Henderson paper to [1-10].
;;; 14-MAY-96 mk    Added entry for Visual Prolog to part 2.
;;; 14-MAY-96 mk    Updated LPA Prolog entry.
;;; 14-MAY-96 mk    Prolog Vendors' Group renamed Prolog Management Group, and
;;;                 email address changed due to Al Roth's death earlier this
;;;                 year.

*** Topics Covered:

There are currently two parts to the PRG:

   1. Introductory Matter and General Questions
   2. Prolog Implementations

Table of Contents (Part 1):

  [1-0]  Introduction
  [1-1]  Sources of information about Prolog
  [1-2]  Prolog and Logic Programming Related Mailing Lists
  [1-3]  Books and Magazine Articles
  [1-4]  Prolog and Logic Programming Associations and Journals
  [1-5]  FTP Archives and Other Resources
  [1-6]  Free Object-Oriented Systems for Prolog
  [1-7]  Commercial Object-Oriented Systems for Prolog
  [1-8]  The Prolog 1000 Database
  [1-9]  X-Windows Interfaces
  [1-10] Is there a straight-forward way of compiling Prolog to C?
  [1-11] WAM emulators and tracers
  [1-12] What is the Basic Andorra Model and AKL?
  [1-13] What is Constraint Logic Programming?
  [1-14] How do you write portable programs in Prolog?
  [1-15] World-Wide Web (WWW) Resources
  [1-16] Prolog Job Postings
  [1-17] Is Prolog really used in Windows NT?
  [1-18] History of Prolog
  [1-19] The ISO Standard for Prolog and other Prolog standards
  [1-A]  Acknowledgements

Prolog Implementations (Part 2):

  [2-0]  General information about Prolog Implementations
  [2-1]  Free Prolog Implementations
  [2-2]  Commercial Prolog Implementations
  [2-3]  Free Parallel Prolog Implementations
  [2-4]  Commercial Parallel Prolog Implementations
  [2-5]  Free Constraint Systems
  [2-6]  Commercial Constraint Systems
  [2-7]  Free Logic Programming Systems
  [2-8]  Commercial Logic Programming Systems
  [2-9]  Other Commercial Prolog Products
  [2-10] Prolog extensions, meta-interpreters, and pre-processors

Search for [#] to get to topic number # quickly. In newsreaders which
support digests (such as rn), [CTRL]-G will page through the answers.

Subject: [1-0] Introduction Certain questions and topics come up frequently in the various network discussion groups devoted to and related to Prolog and logic programming. This file/article is an attempt to gather these questions and their answers into a convenient reference for Prolog programmers. It (or a reference to it) is posted periodically. The hope is that this will cut down on the user time and network bandwidth used to post, read and respond to the same questions over and over, as well as providing education by answering questions some readers may not even have thought to ask. This guide lists Prolog and logic programming resources: archives, newsgroups, books, magazines, compilers, interpreters and anything else you can think of which has to do with the proliferation of Prolog and logic programming. Also included is a list of suppliers of products and a list of publishers. Topics can also include unification, backtracking search, and other aspects of logic programming. As Prolog has a strong historical tradition in Europe, we've tried to ensure that the information is relevant to all readers, including European and North American. This is not a Prolog tutorial, nor is it an exhaustive list of all Prolog intricacies. Prolog is a very powerful and expressive language, but with that power comes many complexities. This list attempts to address the ones that average Prolog programmers are likely to encounter. If you are new to Prolog, read one of the introductions listed in the answer to question [1-3]. Please do not post homework questions to the comp.lang.prolog newsgroup. You won't learn anything if somebody else does the problem for you, and won't get any credit for your answer if your instructor reads the newsgroup. Please also avoid starting the debate on which language is better; Prolog or Lisp, Prolog or C, and so on. Such discussions are rarely productive, and nobody will change their opinion as a result of the debate. The usual conclusion of such debates is that the languages are Turing equivalent, but some languages are better suited for particular tasks. For Prolog, the consensus is that it is a good choice for problems involving logic and problems whose solution can be represented or characterized succinctly in logical form. Some folks feel Prolog is the best language for natural language processing; others disagree. The comp.lang.prolog newsgroup is archived in on a weekly basis. This guide is posted regularly to comp.lang.prolog and comp.object.logic. It may also be obtained by anonymous ftp from [] using username "anonymous" and password "name@host" (substitute your email address) or via AFS in the Andrew File System directory /afs/ as the files prg_1.faq and prg_2.faq. You can also obtain a copy of the FAQ by sending a message to with Send PRG in the message body. The FAQ postings are also archived in the periodic posting archive on [] If you do not have anonymous ftp access, you can access the archive by mail server as well. Send an E-mail message to with "help" and "index" in the body on separate lines for more information. An automatically generated HTML version of the PRG is accessible by WWW as part of the AI-related FAQs Mosaic page. The URL for this resource is The direct URL for the PRG is If you need to cite the FAQ for some reason, use the following format: Mark Kantrowitz, "Prolog Resource Guide", comp.lang.prolog, <month>, <year>,, Disclaimer: We have taken great care in making the information in this document as accurate as possible. However we are not responsible for any problems which might occur from using information supplied in this guide.
Subject: [1-1] Sources of Information about Prolog The newsgroups comp.lang.prolog, comp.object.logic, and (to a lesser extent) are a source of information and discussion about Prolog. See also sci.logic. The newsgroup comp.constraints is for information about constraint processing languages and related topics. A "Frequently Asked Questions" posting is posted to comp.lang.prolog twice a month by Jamie Andrews <>. The Prolog FAQ and this Prolog Resource Guide are intended to complement one another. Several WWW resources are available (see also [1-5] and [1-15]): CMU Prolog Repository. Extensive archives of code, bibliographies, FAQs, newsgroup postings, tech reports, and more. The URL is: NALP: North American Logic Programming. World-wide coverage with some emphasis on developing LP in North America. The URL is: Logic Programming Archive at Oxford Comlab. World-wide coverage with emphasis on Europe. The URL is:
Subject: [1-2] Prolog and Logic Programming Related Mailing Lists Prolog and Logic Programming: (general) (nitty gritty) All requests to be added to or deleted from this list, problems, questions, etc., should be sent to [The host no longer exists, as of 11/24/92. Does anybody know the new location of the mailing lists?] Lambda Prolog: To subscribe, send mail to Mercury: (announcements) (general discussion) To subscribe, send mail to and/or (respectively) with "subscribe" in the message body. Electronic Journal of Functional and Logic Programming (EJFLP) EJFLP is a refereed journal that will be distributed for free via e-mail. The aim of EJFLP is to create a new medium for research investigating the integration of the functional, logic and constraint programming paradigms. For instructions on submitting a paper, send an empty mail message with Subject: Help to: You will receive an acknowledgment of your submission within a few hours. To subscribe to the journal, send an empty mail message to the following address: You will receive an acknowledgment of your subscription within a few days. If there are any problems with the mail-server, send mail to The editorial board is: Rita Loogen (RWTH Aachen), Herbert Kuchen (RWTH Aachen), Michael Hanus (MPI-Saarbruecken), Manuel MT Chakravarty (TU Berlin), Martin Koehler (Imperial College London), Yike Guo (Imperial College London), Mario Rodriguez-Artalejo (Univ. Madrid), Andy Krall (TU Wien), Andy Mueck (LMU Muenchen), Tetsuo Ida (Univ. Tsukuba, Japan), Hendrik C.R. Lock (IBM Heidelberg), Andreas Hallmann (Univ. Dortmund), Peter Padawitz (Univ. Dortmund), Christoph Brzoska (Univ. Karlsruhe). [The JFLP is now being published by MIT Press. Please see the JFLP web page at the URL or the MIT Press web page at or send email to for further information.] PDC-L: is a discussion list for PDC Prolog users. To subscribe, send mail to with SUBSCRIBE PDC-L <your full name> in the message body. Theorem Provers: This (unmoderated) list is intended for announcements of interest to people interested in automated theorem proving. To subscribe, send your email address to Type Theory: Moderated mailing list about type theory. Archived on To subscribe, send mail to Logic: Moderated mailing list about logic. Archived on To subscribe, send mail to ALP (French Chapter): La liste de diffusion "prog-logique" est le support electronique de communication de la section francaise de l'ALP (Association for Logic Programming), groupe de travail AFCET. Elle complete la lettre du groupe publiee trimestriellement. Pour vous abonner ou vous desabonner, il faut envoyer un "mail" au serveur de listes, a l'adresse sans sujet ni signature, et dont le corps du message contient SUB prog-logique Prenom Nom Un acquittement est renvoye par messagerie. Pour desabonnement, ecrit SIGNOFF prog-logique Les requetes envoyees directement a la liste ne seront pas prises en compte.
Subject: [1-3] Books and Magazine Articles A BiBTeX bibliography of Logic Programming Conferences is available by anonymous ftp from See [1-5] below. A partially annotated bibliography of work on integrating object-oriented and logic programming is available by anonymous ftp from in PostScript and BibTeX formats. Written by Vladimir Alexiev <>. The following books are regarded as popular and widely used. Also included are some books about WAM. This is not intended to be a complete Prolog bibliography. Prolog Programming: Covington, Michael A.; Nute, D.; and Vellino, A. "Prolog Programming in Depth", Scott, Foresman & Co., 1987. ISBN 0-521-40984-5 (Out of print, but new edition coming soon. Copies of the 1987 edition are still available from the University of Georgia Bookstore, at 706-542-7131.) Book source code available at: Bowen, Kenneth A. "Prolog and Expert Systems", Mcgraw-Hill, Inc., 1991, ISBN 0-07-006731-7 ($29.95). Book source code available at: Clocksin, W.F. and Mellish, C.S: "Programming in Prolog", 3rd Ed. Springer Verlag, 1987. 281 pages, ISBN 0-387-17539-3 ($29). [Basic introduction to Prolog.] Coelho, H., and Cotta, J.C., "Prolog by Example", Springer Verlag, 1988. 381 pages, ISBN 0-387-18313-2 ($39.50). Cooke, Daniel E., "Logic: The Basis for Understanding Prolog", Ablex, Norwood, NJ, 1994. 224 pages, ISBN 1-56750-028-5 ($27.50). [Intro to Prolog with a review of the basic ideas underlying the language.] Conlon, Tom: "Programming in Parlog". Addison-Wesley, 1989, ISBN 0-201-17450-2. Dawe, C.M. and M.S. Dawe, "Prolog for Computer Science", Springer Verlag, 1994. 190 pages, ISBN 0-387-19811-3 paper ($35). [Intro to computer science using Prolog.] Dodd, Anthony, "Prolog: A logical approach", Oxford University Press, New York, 1990, 556 pages. ISBN 0-198-53822-7 (cloth), $52.50; ISBN 0-198-53821-9 (paperback), $26.00. Kluzniak and Szpakowicz: "Prolog for Programmers", Academic Press 1985 G. L. Lazarev, "Why Prolog? Justifying Logic Programming for Practical Applications", Prentice Hall, 1989. [Software engineering bent. Emphasizes advantages of declarative programming.] Le, Tu Van, "Techniques of Prolog programming, with implementation of logical negation and quantified goals", John Wiley, New York, 1993. ISBN: 0-471-57175-X (American edition), 0-471-59970-O (International edition). LnProlog, a Prolog interpreter that supports negative finding queries and quantified queries is available together with the book. Saint-Dizier, P., "An Introduction to Programming in Prolog", Springer Verlag, 1990. 184 pages, ISBN 0-387-97144-0 paper ($25). [Tutorial introduction, with simple examples of AI programs and games.] Leon Sterling, editor, "The Practice of Prolog", MIT Press, 1990. 342 pages, ISBN 0-262-19301-9, $39.95. Advanced Prolog Programming: O'Keefe, Richard A., "The Craft of PROLOG", MIT Press, 1990, 410 pages. ISBN 0-262-15039-5, $42.50. Peter Ross, "Advanced Prolog: Techniques and Examples", Addison-Wesley, 1989, ISBN 0-201-17527-4. Leon Sterling and Ehud Shapiro, "The Art of Prolog: Advanced Programming Techniques", 2nd Edition, MIT Press, 1994. 688 pages, ISBN 0-262-19338-8 ($49.95). [Source code for the book is available in There is a subdirectory for each chapter of the book containing the text of the programs in that chapter.] AI and Prolog: Yoav Shoham, "Artificial Intelligence Techniques in Prolog", Morgan Kaufmann Publishers, 1993, 400 pages. ISBN 1-55860-167-8 (paper) $39.95. ISBN 1-55860-319-0 (cloth) $49.95. [Topics include search, backward chaining, data-driven methods, truth maintenance, constraint satisfaction, reasoning with uncertainty, planning, temporal reasoning, machine learning, and natural language processing. Prolog source for all the programs in the book is available by anonymous ftp from Bratko, Ivan, "Programming in Prolog for Artificial Intelligence", 2nd Edition, Addison-Wesley, 1990. [Good introduction to Prolog and AI. A bit large, though, for an Intro to Prolog course. Includes discussion of the 8-queens problem.] Dennis Merritt, "Building Expert Systems in Prolog", Springer-Verlag, 1989. 358 pages, ISBN 0-387-97016-9 hardcover ($52). Explains how to build various expert system shells in Prolog, including forward/backward chaining, FOOPS, rete-network, frames, solving Rubik's cube and more. Includes complete source code listings. (Source code from the book is also sold on disk by Amzi! Inc. and is available by anonymous FTP from as the files xsip.*) Dennis Merritt: "Adventure in Prolog", Springer-Verlag, 1990. 186 papers, ISBN 0-387-97315-X hardcover ($38). Teaches Prolog by leading the reader through the construction of an adventure game. The exercises lead the reader through three other programs: an intelligent database, an expert system and an order-entry program. While most texts teach Prolog with fragments of interesting code, this book takes a more pragmatic (as opposed to theoretical approach) and shows the reader how to assemble complete Prolog programs. Gazdar, G. and Mellish, C., "Natural Language Processing in Prolog: An Introduction to Computational Linguistics", Addison-Wesley, Reading, Massachusetts, 1989. (There are three different editions of the book, one for Lisp, one for Prolog, and one for Pop-11.) Fernando C.N. Pereira and Stuart M. Shieber, "Prolog and Natural-Language Analysis", CSLI Lecture Notes Number 10, Stanford, CA, 1987. 286 pages, ISBN 0-937073-18-0. Michael A. Covington, "Natural Language Processing for Prolog Programmers", Prentice-Hall, Englewood Cliffs, NJ, 1994. ISBN 0-13-629213-5. Harvey Abramson and Veronica Dahl, "Logic Grammars", Springer-Verlag, New York, 1989, 234 pages, ISBN 0-387-96961-6. Peter Flach, "Simply Logical: Intelligent Reasoning by Example", John Wiley & Sons, 1994, 256 pages. ISBN 0-471-94152-2 paper ($31.95). [Covers theoretical and practical aspects of Prolog programming as well as AI topics like knowledge representation, search, heuristics, abduction, default reasoning, and induction. Every technique is accompanied by a Prolog program that implements it. More information about the book is available from or by email from] Prolog and Object-Oriented Programming: Chris Moss, "Prolog++ The Power of Object-Oriented and Logic Programming", Addison-Wesley, 1994. 312 pages, ISBN 0-201-56507-2. UK price is 21.95 pounds. [This paperback includes a special offer to obtain a Prolog++ compiler from LPA for Windows 3.1 or Macintosh. UK price is 29.95 pounds (plus 17.5 percent VAT) plus 5.00 pounds postage and handling. Elsewhere the cost is $49.95 plus $8 p&h.] Logic Programming: Hogger, Christopher J., "Introduction to Logic Programming", Academic Press, 1984. 278 pages. ISBN 0-12-352090-8 (alk. paper) ISBN 0-12-352092-4 (pbk.). Hogger, Christopher J., "Essentials of Logic Programming", Clarendon Press, Oxford, 1990. ISBN 0-19-853820-0. [Covers both foundations and more practical material, relating it all to Prolog. Takes a different approach than his first intro, dividing the book into many short "themes" instead of chapters, and including many excercises (with some answers).] Kowalski, R.A.: "Logic for Problem Solving", New York 1979, Elsevier Publ. LLoyd, John: "Foundations of Logic Programming", 2nd Edition, Springer-Verlag, 1988. (Intro to logic programming theory.) David Maier and David S. Warren: "Computing with Logic: Logic Programming with Prolog", Benjamin Cummings, Menlo Park, CA, 1989. Nilsson, Ulf and Maluszynski, Jan, "Logic, Programming and Prolog", John Wiley & Sons, 1990, ISBN 0-471-92625-6. Subrata Kumar DAS, "Deductive Databases and Logic Programming", Addison-Wesley Publishing Company, July 1992, 448 pages. ISBN 0-201-56897-7. Constraint Logic Programming and Constraint Satisfaction: Bennaceur, Hachemi and Gerard Plateau, "An exact algorithm for the constraint satisfaction problem: Application to logical inference", Information Processing Letters 48(3):151-158, November 19, 1993. Cohen, J., "Constraint Logic Programming Languages", Communciations of the ACM 33(7):52-68, 1992. [Good introduction to CLP and includes a historical overview.] Freeman-Benson, B.N., Maloney, J., and Borning, A., "An Incremental Constraint Solver", Communications of the ACM 33(1):54-63, 1990. [Includes a good reading list on the history and applications of constraints.] Freuder, Eugene C., and Richard J. Wallace, "Partial constraint satisfaction", Artificial Intelligence 58(1-3):21-70, December 1992. Van Hentenryck, Pascal, "Constraint Satisfaction in Logic Programming", MIT Press, Cambridge, MA, 1989, ISBN 0-262-08181-4. Jaffar, Joxan and Jean-Louis Lassez, "Constraint Logic Programming", in Proceedings of the 14th ACM Symposium on Principles of Programming Languages (POPL), Munich, Germany, pages 111-119, 1987. [A longer version appears in Joxan Jaffar and Jean-Louis Lassez, "Constraint Logic Programming", Technical Report 86-74, Monash University, Victoria, Australia, June 1986.] Kumar, Vipin, "Algorithms for Constraint-Satisfaction Problems: A Survey", AI Magazine 13(1):32-44, 1992. Mackworth, Alan K., "The logic of constraint satisfaction", Artificial Intelligence 58:3-20, 1992. Meseguer, P., "Constraint Satisfaction Problems: An Overview", AICOM 2(1):3-17, 1989. Steele, Guy L., "The Definition and Implementation of A Computer Programming Language Based on Constraints", PhD thesis, MIT, 1980. Tsang, Edward, "Foundations of Constraint Satisfaction", Academic Press, 1993. 421 pages, ISBN 0-12-701610-4 ($75). [Good overview.] Zhang, Ying and Alan K. Mackworth, "Constraint Programming in Constraint Nets", in Position Papers for the First Workshop on Principles and Practice of Constraint Programming, pages 303-312, Newport, RI, April 28-30, 1993. [See also the articles on Constraint Networks (pages 276-285) and Constraint Satisfaction (pages 285-293) in Shapiro's Encyclopedia of Artificial Intelligence.] Prolog Implementations and WAMs: Ait-Kaci, Hassan, "Warren's Abstract Machine: A Tutorial Reconstruction", MIT Press, Cambridge, MA. 1991. 125 pages, ISBN 0-262-51058-8 paper ($17.50), 0-262-01123-9 cloth. Patrice Boizumault, "The Implementation of Prolog", Princeton University Press, Princeton, NJ, 1993. Translated by Ara M. Djamboulian and Jamal Fattouh. ISBN 0-691-08757-1, 357 pages ($49.50). [The interpreters developed in the book are available by anonymous ftp from See [2-1].] Campbell, J.A. (ed): "Implementations of Prolog", John Wiley, 1984 Peter M. Kogge, "The Architecture of Symbolic Computers", McGraw-Hill, 1991. ISBN 0-07-035596-7. Includes sections on memory management, the SECD and Warren Abstract Machines, and overviews of the various Lisp Machine architectures. David Maier and David S. Warren, "Computing with Logic: Logic Programming with Prolog", Benjamin/Commings Publishing Co., 1988. ISBN 0-8053-6681-4. David H. D. Warren: "An Abstract Prolog Instruction Set", Technical Note No 309, SRI International, Menlo Park, CA, 1983. David H. D. Warren, "Logic Programming and Compiler Writing," in Software-Practice and Experience 10(2):97-125, 1980. J. Cohen and T. Hickey, "Parsing and Compiling using Prolog", ACM Transactions on Programming Languages and Systems (TOPLAS), 9(2):125-163, 1987. J. Paakki, "Prolog in practical compiler writing", The Computer Journal 34(1):64-72, 1991. (But see Letters to the Editor, The Computer Journal 35(3):313, 1992.) Jonathan P. Bowen, "From Programs to Object Code using Logic and Logic Programming", in R. Giegerich and S. L. Graham, editors, Code Generation -- Concepts, Tools, Techniques, pages 173-192, Springer-Verlag, 1992. Jonathan P. Bowen, "From Programs to Object Code and back again using Logic Programming: Compilation and Decompilation", Journal of Software Maintenance: Research and Practice 5(4):205-234, December 1993. Parallel Prologs: Gregory, Steve: "Parallel Logic Programming in Parlog: The Language and Its Implementation", Addison-Wesley, 1987, ISBN 0-201-19241-1. Tick, E.: "Parallel Logic Programming". MIT Press, 1991 Miscellaneous: Deville, Yves: "Logic Programming, Systematic Program Development", International Series in Logic Programming, Addison-Wesley, 1990, 338 pages. ISBN 0-201-17576-2. Wolfram, D.A., "The Clausal Theory of Types", Cambridge Tracts in Theoretical Computer Science {\bf 21}, Cambridge University Press, 1993. Magazine Articles: PCAI Magzine, September/October 1993. Article on exploring Prolog, showing the first steps to four applications -- an adventure game, an object-oriented shell, a tax program, and an animal guessing game. An excerpt of this article is available from BYTE Magazine, August 1987. 5 introductory articles on Prolog. Applications include logic grammars and simulating a microprocessor. Uwe Schreiweis: Beredte Logik, Konzepte der 'KI-Sprache" Prolog, (Eloquent Logic, Concepts of the AI language Prolog), iX Magazine, October 1992, pages 84-90. Uwe Schreiweis: Basis der Fuenf, Die Sprache Prolog in der Public Domain, (Base of the Five, Prolog in the Public Domain), iX Magazine, October 1992, pages 92-94. Uwe Schreiweis: Fuenfte Generation, Kommerzielle Prolog-Systeme, (Fifth Generation, Commercial Prolog Systems), iX Magazine, October 1992, pages 96-102. Klaus Bothe: Weniger Raum, Speicherplatzbezogener Prolog-Benchmark, (Less Space, A Space Oriented Prolog Benchmark), iX Magazine, October 1992, pages 106-7. Magazines Related to Prolog: Logic Programming Newsletter (4 issues/yr) Included with membership in the Association for Logic Programming ($30 regular, $15 students). For membership information, write to Valerie Anderson (ALP), DoC-ICSTM, 180 Queens Gate, London SW7 2BZ, UK, phone +44-171-594-8226, fax +44-171-589-1552, or send email to Contributions are welcome and should be sent to Andrew Davidson <>. Selected articles from the newsletter are available from the WWW archive AI Communications (4 issues/yr) "The European Journal on Artificial Intelligence" ISSN 0921-7126, European Coordinating Committee for Artificial Intelligence. AI Expert (issued monthly) ISSN 0888-3785, Miller Freeman Publishers See a copy of the magazine for list of BBS's in NA. On CompuServe: GO AIEXPERT. Regularly reviews Prolog interpreters and compilers. -- Ceased publication in June, 1995. PC AI (issued bi-monthly) ISSN 0894-0711, Knowledge Technology Inc. Regularly reviews Prolog systems and applications. See Expert Systems (issued Feb, May, Aug and Nov) ISSN 0266-4720, Learned Information (Europe) Ltd. Subscription: GBP 85 or USD 110 IEEE Expert (issued bimonthly) ISSN 0885-9000, IEEE Computer Society The Journal of Logic Programming (issued bimonthly), (North-Holland), Elsevier Publishing Company, ISSN 0743-1066 New Generation Computing, Springer-Verlag. (LOTS of Prolog in it.)
Subject: [1-4] Prolog and Logic Programming Associations and Journals ASSOCIATION FOR LOGIC PROGRAMMING (ALP) Members receive the ALP Newsletter. For information on membership ($30 regular, $15 students), contact Valerie Anderson ALP Administrative Secretary Department of Computing Imperial College 180 Queen's Gate London, SW7 2BZ, UK Email: Fax: +44 171 589 1552 Phone: +44 171 594 8226 Newsletter submissions should be sent to Andrew Davison Department of Computer Science University of Melbourne Parkville Melbourne, Victoria 3052 AUSTRALIA Email: Fax: +61 3 348 1184 Phone: +61 3 344 7207 / 5230 Telex: AA 35185
Subject: [1-5] FTP Archives and Other Resources The following are achives that contain Prolog-related material, such as code, interpreters, articles, etc. Most of the archives are ftp sites. They are listed by and [IP Address]. To access them and download programs type at the prompt: ftp <site name> (or IP address) login: "anonymous", password: your own return email address, cd <directory>, ls to see files, set binary, get <filename> to transfer file to your system stop with quit or exit Deviations from this general scheme may occur but the above should work in most cases. CMU AI Repository, Prolog Section: The Prolog Section of the CMU Artificial Intelligence Repository (aka "The Prolog Repository") is accessible by anonymous ftp to [] through the AFS directory /afs/ or by WWW from the URL and includes more than 110 megabytes of sources and other materials of interest to Prolog programmers, including all freely distributable implementations and many programs. The contents of the CMU AI Repository has been keyword indexed to provide convenient browsing of the contents. The repository has standardized on using 'tar' for producing archives of files and 'gzip' for compression. To search the keyword index by mail, send a message to: with one or more lines containing calls to the keys command, such as: keys prolog gui in the message body. Keywords may be regular expressions and are compared with the index in a case-insensitive conjunctive fashion. You'll get a response by return mail. Do not include anything else in the Subject line of the message or in the message body. For help on the query mail server, include: help instead. A Mosaic interface to the keyword searching program is in the works. We also plan to make the source code (including indexes) to this program available, as soon as it is stable. Most of the Prolog Section of the AI Repository appears on Prime Time Freeware for AI, Issue 1-1, a mixed-media book/CD-ROM publication. It includes two ISO-9660 CD-ROMs bound into a 224 page book and sells (list) for US$60 plus applicable sales tax and shipping and handling charges. Payable through Visa, Mastercard, postal money orders in US funds, and checks in US funds drawn on a US bank. For more information write to Prime Time Freeware, 370 Altair Way, Suite 150, Sunnyvale, CA 94086 USA, call 408-433-9662, 408-433-0727 (fax), or send email to Contributions of software and other materials are always welcome but must be accompanied by an unambiguous copyright statement that grants permission for free use, copying, and distribution -- either a declaration by the author that the materials are in the public domain, that the materials are subject to the GNU General Public License (cite version), or that the materials are subject to copyright, but the copyright holder grants permission for free use, copying, and distribution. (We will tell you if the copying permissions are too restrictive for us to include the materials in the repository.) Inclusion of materials in the repository does not modify their copyright status in any way. Materials may be placed in: When you put anything in this directory, please send mail to giving us permission to distribute the files, and state whether this permission is just for the AI Repository, or also includes publication on the CD-ROM version (Prime Time Freeware for AI). We would also appreciate if you would include a 0.doc file for your package; see /user/ai/new/package.doc for a template. (If you don't have the time to write your own, we can write it for you based on the information in your package.) The Prolog Section of the AI Repository is maintained by Mark Kantrowitz <>. Artificial Intelligence Programs: [] The University of Georgia AI FTP Library contains public domain Prologs, such as Open Prolog and ESL PD Prolog, PrEd (a small text editor for Prolog), and some miscellaneous prolog programs in A copy of the programs from the book by Covington, Nute, and Vellino, (see the section on Books below), is in and the draft ISO standard for prolog is in Some technical reports with accompanying code are in Other materials of interest are in Maintained by Michael Covington <>. ALE: ALE (Attribute Logic Engine), a freeware system written in Prolog, integrates phrase structure parsing and constraint logic programming with typed feature structures as terms. Types are arranged in an inheritance hierarchy and specified for the features and value types for which they are appropriate. Grammars may also interleave unification steps with logic program goal calls (as can be done in DCGs), thus allowing parsing to be interleaved with other system components. While ALE was developed to handle HPSG grammars, it can also execute PATR-II grammars, DCG grammars, Prolog, Prolog-II, and LOGIN programs, etc. Grammars and programs are specified with a version of Rounds-Kasper Attribute Value Logic with macros and variables. ALE supports lexical rules and empty categories for grammars, using a bottom-up, all-paths dynamic chart parser. ALE supports last call optimization, negation by failure and cuts in definite clauses, which may be used independently or integrated into grammars. The system is distributed with several sample grammars, including a fairly comprehensive implementation of a head-driven phrase structure grammar for English. Version 2.0 of ALE is available free for research purposes by anonymous ftp from as the files ale.*, or from the CMU AI Repository in For more information write to Bob Carpenter <> or Gerald Penn <>. ALP-UK Library: The best Prolog library currently is the one collected by the ALP-UK group. It is available to members at 30 pounds sterling for a Sun cartridge or 2 pounds/IBM DOS disk. (non-members maybe, how much?) It contains MBs of Prolog systems (including SB Prolog), libraries (including the Edinburgh library), benchmarks, grammars, theorem provers, object and graphics systems etc. For more information, write to ALP-UK Library, Sanjay Raina, Librarian, Dept. of Computer Science, University of Bristol, University Walk, Bristol BS8 1TR, UK, call +44 0272 303030 x3304, or send email to CASLOG CASLOG (Complexity Analysis System for LOGic) is an experimental semi-automatic complexity analysis system for logic programs. It can perform the worst-case analysis for complexity measures: argument size complexity, number of solutions complexity, and time complexity. CASLOG extends the techniques developed for analyzing imperative and functional languages to deal with nondeterminism and generation of multiple solutions via backtracking in logic languages. The analyses for different complexity measures are implemented in a unified framework and share several common features. First, the predicates in a program are processed in an order generated by a bottom-up topological sorting over the call graph of the program. Second, the complexity function for a predicate is derived from the complexity function of its clauses by using the information about the mutual exclusion relationships between its clauses. Third, the complexity function for a clause is inferred based on the data dependency relationships between its literals. Fourth, the complexity functions for recursive clauses are in the form of difference equations and are transformed into closed form functions using difference equation solving techniques. This unified framework can simplify proofs of correctness and the implementation of the algorithms. CASLOG is available by anonymous ftp from This is an alpha distribution, and includes CASLOG version 1.0, a preliminary user manual, a paper on CASLOG, and a set of examples. For more information, contact Nai-Wei Lin <>. Constraint Programming Paper Archive: Aarhus University, Denmark, has established an anonymous ftp archive for papers on "Constraint Programming" at For further information, contact Brian H. Mayoh <>. CSP: Some constraint-related papers by a research group at the University of Washington are available by anonymous ftp from The papers from the 1994 Principles and Practice of Constraint Programming Workshop are available in There are also implementations of several constraint satisfaction algorithms and constraint-based systems, including the DeltaBlue and SkyBlue algorithms, the Multi-Garnet user interface toolkit, ThingLab II, and CoolDraw (a constraint-based drawing system), in subdirectories of The ftp archive is also accessible via WWW: All the source code is in the public domain. For more information, write to Alan Borning <>. C implementations of a number of constraint satisfaction algorithms are available by anonymous ftp from Get the files README and csplib.tar.Z. The algorithms include variations on backtracking (backjumping, backmarking, chronological backtracking, etc.), local consistency preprocessing algorithms (e.g., arc consistency), and random problem generators. For more information, write to Peter van Beek <>. Eden: Eden is a Poplog-based AI microworld developed by Simon Perkins, Jocelyn Paine and Edmund Chattoe of the Oxford University Artificial Intelligence Society. It is intended to serve as a testbed for learning and planning programs. Programs written in Pop-11, Prolog, Lisp, and ML control a "bug" that lives in a 2-dimensional world. Any kind of algorithm may be used to control the bug, including genetic algorithms, neural nets, and rule-based systems. Eden consists of a grid of cells, each of which can contain objects such as keys, doors, boulders and quicksand. Bug's objective is to find and eat a piece of food which the simulator has placed somewhere within this grid. To do this, Bug must negotiate its way towards the food while dealing intelligently with obstacles. Eden's laws of physics allow Bug to take one of several different actions when it encounters an object. The simulator then works out the consequences of the chosen action on Bug and on Eden, and displays these graphically in a Ved window. Bug's perceptions are updated to reflect the new state of the world, and the cycle repeats. Eden is available by anonymous ftp from the Imperial College archive in [] as the file eden.tar.Z. (Note: This is really a link to the directory computing/programming/languages/prolog/pd-software/.) Eden includes PopBeast, a simple Prolog bug which can read and parse simple commands, extract their meaning, plan how to satisfy these commands, and then carry out the plans. Parts of the current Eden are coded in Pop-11, so porting it to Prologs other than Poplog will require some effort. Most of the recoding needed is in the grid-world simulator and the definition of objects. Send mail to Jocelyn Paine <> if you're willing to try this. FW_Rules: FW_RULES is a Sicstus Prolog library providing a compiler for forward chaining rules. The implementation is based on a non-state saving technique coupled with an indexing mechanism on the working memory based on C bitwise operations to achieve efficiency. The library supports interoperability between the forward chaining language and the underlying Prolog engine. Terms in the working memory are represented as Prolog facts and can be accessed from Prolog to perform deduction. It is available by anonymous FTP from as the files README and fw_rules.tar.Z. For more information, please write to Mauro Gaspari <>. HDRUG: Hdrug is an environment to develop logic grammars, parsers, and generators for natural languages. The package comes with a number of example grammars, including a Categorial Grammar, a Tree Adjoining Grammar, a Unification Grammar in the spirit of Head-driven Phrase Structure Grammar, an Extraposition Grammar, a Definite Clause Grammar, and a port of the HPSG grammar from Bob Carpenter's ALE system. Each of the grammars comes with a set of parsers, such as Earley-like chart parsers, left-corner parsers and head-driven parsers. Some grammars come with variants of the head-driven generator. The package allows easy comparison of different parsers/generators, extensive possibilities of compiling feature equations into Prolog terms, graphical (Tk), LaTeX and ordinary Prolog output of trees, feature structures and Prolog terms, and plotted graphs and tables of statistical information. Hdrug runs in Sicstus Prolog and requires ProTcl and Tcl/Tk. It is available by anonymous FTP from or by WWW from For more information, write to Gertjan van Noord <>. Logic Programming Bibliographies: [] The ftp server supports tar'ing on the fly, so if you type "get bibtex.tar" you will get a tar'ed version of the "bibtex" directory. BibTeX entries for the proceedings of the following conferences are included: SLP84-87,91, NACLP89-90, ILPS91, ICLP82,84,86-91,93, JICLP92, LP88, RTA89,93, PLILP90-92, ALPUK91, ICOT92, ALP90,92, CADE90,92, CTRS90,92, LICS86-91, UNIF89, EPIA89,91,93, TACS91, TAPSOFT93, EAIA90, FGCS92, FAC, ILPS93, PEPM91,93 and the following journals: JLP85-93, JAR91-93, JSC91-93, IANDC82-92. The bibliography is mirrored by the Universidade Nova de Lisboa. In addition, the bibliography can be searched using either WAIS or GOPHER. To search the lp-proceedings using WAIS, use the lp-proceedings.src wais source, available from the directory of servers. To search the lp-proceedings using GOPHER, point the client to, and follow the directories "Research/Bibliography/Logic Programming Proceedings". Searching should be easier than retrieving the entire package every time you want to locate a particular article. Send comments and bug reports to Machine Learning Algorithms Implemented in Prolog: In 1988 the Special Interest Group on Machine Learning of the German Society for Computer Science (GI e.V.) decided to establish a library of PROLOG implementations of Machine Learning algorithms. The library includes - amongst others - PROLOG implementations of Winston's arch, Becker's AQ-PROLOG, Fisher's COBWEB, Brazdil's generation of discriminations from derivation trees, Quinlan's ID3, FOIL, IDT, substitution matching, explanation based generalization, inverse resolution, and Mitchell's version spaces algorithm. All algorithms are written in Edinburgh Prolog syntax. Most of the algorithms are copyleft under the GNU General Public License. The programs are currently available via anonymous ftp-server from the GMD: [] They are also available by surface mail from Thomas Hoppe, Projektgruppe KIT, Technische Universitaet Berlin, Franklinstr. 28/29, 10629 Berlin, Germany. Files will be distributed via MS-DOS formated 3.5 inch floppy (double, high and extra-high density), which should be included with your request. You can also get them by sending an email message to Thomas Hoppe (see below). Send additional PROLOG implementations of Machine Learning Algorithms, complaints about them and detected bugs or problems to Thomas Hoppe, <>. Send suggestions and complaints about the ftp library to Werner Emde, Gesellschaft fuer Mathematik und Datenverarbeitung, Bonn, <>. Natural Language Processing in Prolog: The Prolog and DCG programs from Pereira and Shieber's book, "Prolog and Natural Language Analysis", are available by anonymous ftp from See the file README for the conditions under which the material is distributed. If you retrieve the files, please send an email message to the authors letting them know how you plan to use them. For further information, write to Fernando Pereira <> or Stuart Shieber <>. Parser: A parser for standard Prolog text written in C is available by anonymous ftp from It consists of only three modules (tokenizer, parser, and display routine) and an interface module to integrate it with an existing Prolog system. It is completely deterministic and about 10 times faster than O'Keefe's public domain parser written in Prolog. For more information, write to Koen De Bosschere <>. Partial Evaluation: Prolog code for the partial evaluator for the flowchart language described in Ch. 4 of "Partial Evaluation and Automatic Program Generation" by Jones, Gomard and Sestoft is available for anonymous ftp from All three Futamura projections are implemented. The code has been tested under SWI Prolog 1.5 and 1.7 and should hopefully port to other prologs without too many problems. For more information, please contact Zerksis Umrigar <>. Pleuk Grammar Development System: Pleuk is intended to be a shell for grammar development, in that many different grammatical formalisms can be embedded within it. Grammatical formalisms that currently work with Pleuk include CFG (a simple context-free grammar system), HPSG-PL (a system for developing HPSG-style grammars, produced at Simon Fraser University, Canada, by Fred Popowich, Sandi Kodric and Carl Vogel), Mike (a simple graph-based unification system, enhanced with additional operations for the treatment of free word order proposed by Mike Reape in various publications), SLE (a graph-based formalism enhanced with arbitrary relations in the manner of Johnson & Rosner and Doerre & Eisele. Delayed evaluation is used to compute infinite relations. This system has been used for the development of several HPSG-style grammars) and Term (a term-based unification grammar system, originally developed for the support of Unification Categorial Grammar of Zeevat, Klein and Calder). Sample grammars are provided for all of these formalisms. Work continues apace on other formalisms, including Bob Carpenter's Ale system for typed feature structures, and Veronica Dahl's Static Discontinuity Grammars. Pleuk requires SICStus prolog version 2.1#6 or later, plus a variety of ancillary programs available free of charge from many FTP servers. Pleuk is available via anonymous FTP from the University of Georgia Artificial Intelligence FTP library as the files pleuk.1.0.tar.Z, pleuk.PSmanuals.tar.Z, and pleuk.README. Pleuk will also be available shortly from the Natural Language Software Registry, German Research Institute for Artificial Intelligence (DKFI), Saarbruecken. For more information, send email to Prolog Repository: Established by Jocelyn Paine of Experimental Psychology, Oxford University in 1987. The current catalogue (January 1991) contains 30 entries. For catalogue, queries and contributions contact POPX at: (internet) or (janet) FTP access is available through the Imperial College archive at [] This is actually a link to the directory /computing/programming/languages/prolog/pd-software/ To access it, cd to either of the above directories via anonymous ftp. The file README gives a brief summary of the contents of the directory and CATALOGUE gives a (long!) description of each entry. Entries include the Logic Programming Tutor from Paine's book, the DEC-10 public-domain library, the Linger natural-language corrector, a simple object-oriented add-on for Prolog, graph utilities, among other things. Files in the archive are also available on MS-DOS floppies for a nominal fee to cover the cost of floppies, postage, and packing. Prolog to SQL Compiler: The Prolog to SQL Compiler translates database access requests, which consist of a projection term and a database goal, to the appropriate SQL query. The compiler is written in standard Edinburgh Prolog and has been ported to a number of Prologs. The code posted to comp.lang.prolog works in ECRC's SEPIA Prolog, but should be easily ported to other Prologs. A detailed tech report on the implementation is available by email from (include your full postal address). The compiler is copyright, but may be used free of charge for non-commercial purposes and redistributed provided the copyright notice is retained intact. PSI: PSI is a handy system for the management and retrieval of your personal data, be it addresses, CD collections, or bibliographic references. It is intended for the non-commercial user. It may not be as full-fledged as some data-base systems, but has some features that you won't find in most commercial systems. Also, you may find it easier to set up and faster to use. PSI is useful for a broad range of data. Indexing with descriptors makes searching for the data you need fast, and the interface to other data-base formats (import and export) is quite powerful. PSI was written in LPA MacProlog and is a "genuine 'double clickable' Mac application". PSI runs on all Macs with System 6 or 7 in 1MB of main memory. As LPA MacProlog isn't yet 32-bit clean, PSI isn't either. Extensive documentation and some examples are included. PSI is available by anonymous ftp from as the file psi-23.hqx. It was also available on a recent Nautilus CD-ROM and will be on the first Info-Mac CD-ROM. Queens and Knights: Queens and Knights are favorite problems for Prolog programmers. A collection of several implementations is available by anonymous ftp from Write to Roland Karlsson <> for more information. Rubik's Cube: Amzi! Inc., the creators of Cogent Prolog, have made sources to Cube Solver II available from their ftp site, It is also available from the Prolog Repository at CMU, in This Prolog program solves Rubik's Cube. The sources include a simple scrolling interface that should work in any Edinburgh standard Prolog. Also included is a ready-made executable for 386 and 486 PCs; it was implemented using Cogent Prolog. For more information, write to Amzi! Inc. (formerly Amziod) <>, 40 Samuel Prescott Dr., Stow, MA 01775, Tel: 508-897-7332. Fax: 508-897-2784. Their Web page is SEL: SEL is a declarative set processing language. Its main features are subset and equational program clauses, pattern matching over sets, support for efficient iteration and point-wise/incremental computation over sets, the ability to define transitive closures through circular constraints, meta-programming and simple higher-order programming, and a modest user-interface including tracing. The language seems well-suited to a number of problems in graph theory, program analysis, and discrete mathematics. The SEL compiler is written in Quintus Prolog and the run-time system is written in C. It generates WAM-like code, extended to deal with set-matching, memoization, and the novel control structure of the language. SEL is available by anonymous FTP from The FTP release comes with a user manual, bibliography of papers (including .dvi files), several sample programs, and source code. For further information, write to Bharat Jayaraman <>. A public-domain WAM emulator, written in C++ by Herve Touati, is available by anonymous FTP from
Subject: [1-6] Free Object-Oriented Systems for Prolog OL(P), Object Layer for Prolog, is an object-oriented extension to Prolog. It provides an object-oriented structuring and reuse mechanism for Prolog in a manner that preserves performance and semantics. The object-oriented layer is compiled into Prolog without introducing any side-effects. OL(P) takes the view of objects as collections of predicates (called methods). To Prolog, OL(P) 1.1 adds objects with methods, data encapsulation, instances, and multiple inheritance. Object methods can access Prolog predicates and vice versa. The OL(P) incremental compiler translates OL(P) programs to Prolog programs that don't need runtime interpretation (e.g., no search is needed for inheritance). OL(P) 1.1 comes with prepared installation for SICStus Prolog and QUINTUS Prolog (both on UNIX), documentation, simple built-in project management, some libraries, and example programs. The source is included, so you can port OL(P) to different platforms, different Prolog systems, and different logic programming languages. OL(P) is available by anonymous ftp from []. Written by Markus P.J. Fromherz <>. LogTalk is a free object oriented extension to the Prolog programming language. It is based on a reflexive architecture intended to provide an open system, easily tailored to user needs. It implements simple inheritance and a delegation mechanism. Logtalk enables users to define new types of slots, each one with its own semantics, that can be reused by any object. It includes features for event-based programming. This enables the creation of elegant solutions to represent and maintain relations that restrict the internal state of participating objects. Logtalk (and more information about it) is available using the URL For more information, write to the author Paulo Moura <>. See Common ESP (CESP) in [2-1] and BeBOP in [2-3].
Subject: [1-7] Commercial Object-Oriented Systems for Prolog LAP is an object-oriented system by Elsa. For more information, write to Elsa Software, La Grange Dame Rose, 6 ave du Marechal Juin, 92366 Meudon-La-Foret Cedex, France, call +33 (1) 46 30 24 55, fax +33 (1) 46 30 55 26, or send email to elsa! SPIRAL is an object oriented system by CRIL for Sun3 and Sun4 under Unix. For more information, write to CRIL, Conception et Realisation, Industriel de Logiciel, 146 bd de Valmy 92707, Colombes Cedex, France, call +33 1 47 69 53 67, or fax +33 1 47 69 53 99. Quintus Prolog (see [2-2]) has an object system documented in and in Peter Schachte's home page, Quintus objects are updateable data structures whose slots can contain Prolog terms. (For increased efficiency, a slot can be constrained to hold a specific C-style type.) Because the objects are updateable, they offer and efficient alternative to storing modifiable data in the Prolog database. See also LPA Prolog ++ in [2-2].
Subject: [1-8] The Prolog 1000 Database The Prolog 1000 is a database of real Prolog applications being assembled in conjunction with the Association for Logic Programming (ALP) and PVG. The aim is to demonstrate how Prolog is being used in the real world and it already contains over 500 programs with a total of well over 2 million lines of code. The database is available for research use in SGML format from the Imperial College archive If you have or know about a program that might qualify for inclusion, send an email message to Al Roth ( for an electronic entry form which only takes a few minutes to complete. Or write to Prolog 1000, PO Box 137, Blackpool, Lancashire, FY2 0XY, U.K., Fax: +44 253 53811 Telephone: +44 253 58081. (Floppy disks for PC or Mac in text form are also welcome, and paper entries may also be sent). Queries may also be addressed to: Chris Moss (, Leon Sterling (
Subject: [1-9] X-Windows Interfaces PI: PI is an interface between Prolog applications and the X Window System that aims to be independent from the Prolog engine, provided that it has a Quintus-style foreign function interface (such as SICStus, YAP). It is mostly written in Prolog and is divided in two libraries: (1) Edipo, a low-level interface to the Xlib functions, and (2) Ytoolkit, a high-level user interface toolkit that allows you to create and manage graphical objects, define new classes of objects, and handle user interaction. PI is available by anonymous ftp from and includes documentation and some demos. Also see ytoolkit.tar.Z. PI has been tested in Quintus Prolog 3.1.1 and SICStus 2.1 #8. Send questions, comments, and bug reports to Ze' Paulo Leal, Universidade de Porto, Portugal, <>. XWIP: (formerly XWIP is an X Windows interface for PROLOG. XPCE: XPCE is an object-oriented X-window interface toolkit for symbolic programming languages (Prolog and Lisp), offering a high level of abstraction for communication with X11, Unix processes, Unix networking facilities (sockets) and Unix files. XPCE's built-in classes (about 150) are mostly written in C. The XPCE/Prolog interface allows the user to create and manipulate instances of these classes. The user can also create new XPCE classes from Prolog. XPCE's window related classes provide various styles of menus, primitive graphical objects, compound graphical objects and Emacs oriented programmable text manipulation windows. The distribution contains several demo programs, including a diagram drawing tool (PceDraw), an animation demo, an Epoch-like editor, a graphical interface to Unix ispell, and an online hyper-text manual for XPCE itself. A demo version of XPCE/SWI-Prolog for Linux may be obtained by anonymous ftp from []. The non-demo versions (for SWI-Prolog, SICStus Prolog, Lucid Common Lisp and LispWorks) require filling out a license and paying a fee (see the file pub/xpce/INFO). To be added to the mailing list send mail to Send bugs to ProWindows 3 is a commercial version of XPCE for Quintus Prolog. For further information, write to Simon Heywood, AI International Ltd, The Chapel, Park View House, 1 Park View Road, Berkhamsted, Herts, HP4 3EY, phone +44-(0)442-876722 (Sales Hotline +44 (0)442 876448), fax +44-(0)442-877997, or send email to ProTcl: ProTcl (pronounced pro-tickle) is a Prolog interface to Tcl/Tk. It has a very simple and lightweight interface, which allows one to evaluate Tcl expressions from Prolog. It defines the tcl_eval/1,2 predicate which passes the Tcl expressions to the Tcl interpreter. It has been tested on ECLiPSe and SICStus, on a Sparc 10. ProTcl is available by anonymous ftp from The ProTCL home page is Send comments and suggestions to Micha Meier <>.
Subject: [1-10] Is there a straight-forward way of compiling Prolog to C? Two methods of compiling Prolog to C have been reported in the literature: - WAM-based approaches - Continuation-based approaches The WAM-based approach compiles Prolog programs into a sequence of C function or macro calls to WAM instructions. A brief description of this method and some results are given in the paper: Michael R. Levy and R. Nigel Horspool, "Translating Prolog to C: a WAM-based Approach", in Proceedings of the Second Compulog Network Area Meeting on Programming Languages, and the Workshop on Logic Languages in Pisa, May 1993. (Available by anonymous ftp from The best tutorial for writing a WAM-based compiler or WAM emulator is Hassan Ait-Kaci's book, "Warren's Abstract Machine: A Tutorial Reconstruction" (see [1-3] above). A "quick-and-dirty" method is to implement the WAM functions as described in Ait-Kaci's tutorial, to label each call with a C case label, and then throw a giant switch(P) statement around the entire sequence of calls, where P is the WAM program counter. On return from any instruction that modifies P, a "goto Start" must be inserted. (This method was posted by Rob Scott, <>, based on the JANUS papers by Saraswat.) This strategy will work, but does not allow you to modularize your prolog program. Predicates in prolog seem to generate 8 to 15 WAM instructions per clause, so (assuming very roughly a clause per line)you might expect your 1,000 line program to expand to a switch statement containing up to 15,000 lines. Some C compilers can't handle such a big switch statement. Levy and Horspool solve this problem by compiling each Prolog predicate to a seperate C function. A dispatch loop mechanism is used to call the C functions. C switch statements are used only inside the functions. A predicate that calls another predicate sets P to contain the address of the C function that implements the called predicate, (and sets another register called W in their scheme) and then returns to the dispatcher instead of calling the predicate. This bypasses the C run-time stack. This lets one exploit WAM optimizations (like LCO) and yet retain the ability to create many modules. Their system performs well when compared with byte-code compilers, but translated code runs slower than code produced by native code compilers. On the other hand, it outputs portable ANSI C that can run on any machine with a C compiler. Henderson, Somogyi, and Conway's paper "Compiling Logic Programs to C using GNU C as a portable assembler" htpp:// mentions some optimizations to the above approach, and also describes another approach used in the Mercury compiler which achieves efficiency comparable to direct native-code generation by using GNU C extensions. They use conditional compilation (#ifdef) to enable use of these extensions, so the generated C code will still run on other ANSI C compilers, although the GNU C extensions improve performance for Mercury by nearly a factor of three. Other approaches to translating to C use continuations. The idea here is to translate every Prolog predicate to a C function that has an additional argument, namely a continuation function. If the function fails, it simply returns, but if it succeeds, it executes the continuation. When the function regains control from the continuation, it can then try to generate a new solution. Here are two references that describe systems built using continuations: J. L. Weiner and S. Ramakrishnan, "A Piggy-Back Compiler for Prolog", in Proceedings of SIGPLAN T88 Conference on Programming Language Design and Implementation, Atlanta, Georgia, 1988, pages 288-296. J. L. Boyd and G. M. Karam, "Prolog in C", Carleton University, Ottawa, 1988. Oliver Ridoux <> reports that a continuation-based approach works well when used to compile LambdaProlog. His scheme translates every predicate into a function that uses and modifies the success and failure continuations, with recursion in the predicate becoming iteration in the continuation passing mechanism. Inside the function one uses whichever intermediate machine one fancies. Clauses within the function can be either the branches of a switch statement or simply labelled when using a C system that can store labels. This approach can still generate monstrous C programs that blow up the C compiler, but the C programs aren't as large as those generated by a one module to a function scheme. Approaches that replace recursion in a predicate with recursion in a function tend to overload the C stack and lead to sloppy memory management. Two technical reports describing Ridoux's approach are available by anonymous ftp from as pm/*.ps.Z and mailv06/*.ps.Z. Michael Covington <> points out that a very simple approach is to write a Prolog interpreter in C, then store the Prolog program in that program's data! This will, of course, execute slowly. One might imagine all sorts of other schemes. For example, a query could be treated as a stack of "suspensions" (with the left-most goal on top). The top suspension is executed by selecting the appropriate clause (possibly using indexing), and then, if necessary, pushing new suspensions on the stack (the body of the clause whose head unified with the current suspension). Another question to ask is this: Is there any reason why you should want to convert Prolog to C at all? George Saab of Quintus Corp. pointed out that, with Quintus Prolog, you can create a standard .o file from a Prolog file, which can then be linked with your other .o files to create an executable. What's more, your Prolog code can be called from C code and vice versa. On ther hand, the advantage of distributing "Prolog objects" as C rather than .o files is portability. M. Gaspari and G. Attardi describe an approach to translating Prolog to C based on the provision of a common runtime architecture. This is described in G. Attardi and M. Gaspari, "Multilanguage Interoperability", in Proceedings of The 3rd International Symposium, PLILP 91, Springer Verlag, LNCS #528, 1991. [Note: Thanks to Michael Levy, Department of Computer Science, University of Victoria, <>, for writing this section.]
Subject: [1-11] WAM emulators and tracers Johan Bevemyr's Luther-based WAM-tracer is available by anonymous ftp from Uppsala University in Sweden. It includes a simple compiler from Prolog to WAM code and a low-level WAM code tracer written in emacs-lisp. The tracer splits the screen into regions to show data-areas, registers, and so on. You can then step through running the code. The tracer is available by anonymous ftp from Documentation on the tracer is included in the distribution. The emulator is in the /pub/WAM-emulator/ directory (and runs in SICStus Prolog). For more information, contact Johan Bevemyr <> or <>.
Subject: [1-12] What is the Basic Andorra Model and AKL? The Basic Andorra Model is a way to execute definite clause programs that allows dependent and-parallelism to be exploited transparently. It also supports nice programming techniques for search programs. The idea is to first reduce all goals that match at most one clause. When no such goal exists, any goal (e.g., the left-most) may be chosen. The BAM was proposed by David H. D. Warren, and his group at Bristol has developed an AND-OR parallel implementation called Andorra-I, which also supports full Prolog. See, for example, Seif Haridi and Per Brand, "Andorra Prolog, an integration of Prolog and committed choice languages", in Proceedings of the FGCS 1988, ICOT, Tokyo, 1988. Vitor Santos Costa, David H. D. Warren, and Rong Yang, "Two papers on the Andorra-I engine and preprocessor", in Proceedings of the 8th ICLP. MIT Press, 1991. Steve Gregory and Rong Yang, "Parallel Constraint Solving in Andorra-I", in Proceedings of FGCS'92. ICOT, Tokyo, 1992. AKL (Andorra Kernel Language) is a concurrent constraint programming language that supports both Prolog-style programming and committed choice programming. Its control of don't-know nondeterminism is based on the Andorra model, which has been generalised to also deal with nondeterminism encapsulated in guards and aggregates (such as bagof) in a concurrent setting. See, for example, Sverker Janson and Seif Haridi, "Programming Paradigms of the Andorra Kernel Language", in Proceedings of ILPS'91. MIT Press, 1991. Torkel Franzen, "Logical Aspects of the Andorra Kernel Language", SICS Research Report R91:12, Swedish Institute of Computer Science, 1991. Torkel Franzen, Seif Haridi, and Sverker Janson, "An Overview of the Andorra Kernel Language", In LNAI (LNCS) 596, Springer-Verlag, 1992. Sverker Janson, Johan Montelius, and Seif Haridi, "Ports for Objects in Concurrent Logic Programs", in Research Directions in Concurrent Object-Oriented Programming, MIT Press, 1993 (forthcoming). The above papers on AKL are available by anonymous ftp from An (as yet non-released) prototype implementation of AKL is available for research purposes (contact
Subject: [1-13] What is Constraint Logic Programming? Constraint Logic Programming (CLP) augments Prolog by adding constraints to the clauses. The CLP implementation solves goals in the same manner as Prolog, but also merges the constraints associated with each rule. If the merge succeeds, the successful goal and the corresponding constraints are returned. If, however, the constraints are mutually exclusive, the solution fails. There is an extensive wide-ranging archive of material relating to constraint logic programming at
Subject: [1-14] How do you write portable programs in Prolog? The de-facto standard syntax for Prolog is known as the Edinburgh standard. It is based on the syntax of DEC-10 Prolog, an early Prolog implementation developed at the University of Edinburgh. See question [1-1] for information on the draft ISO standard for Prolog. Unfortunately, not every Prolog implementation is Edinburgh compatible. There also isn't any notion of read-conditionalization, like #+ and #- *features* in Common Lisp. One option is to use the C preprocessor on Prolog code before loading it into Prolog. Or you could use term-expansion to roll your own conditional compilation system. Term expanding a clause to [] effectively discards it. Another possibility is to conditionalize the execution instead of the compilation. The user would have to uncomment a line like one of the following, % this_is(quintus). % this_is(sicstus). and the code would have to test for the proper literal a :- this_is(quintus), blah, blah, blah. a :- this_is(sicstus), blah, blah, blah. at a slight cost in efficiency. (If you first feed the program through a general partial evaluator, you'll get an equivalent program without the inefficiency. Partial evaluation is in some sense a more powerful and semantically cleaner form of source preprocessing. Given <head> :- <condition>, <rest of body>. If <condition> is always false, we can safely drop the clause. If <condition> is always true, we can drop it from any clauses that include it.) Another possibility is Richard O'Keefe's environment package for Prolog. It was posted to comp.lang.prolog on 1-SEP-94; a copy can be found in
Subject: [1-15] World-Wide Web (WWW) Resources The World Wide Web (WWW) is a hypermedia document that spans the Internet. It uses the http (HyperText Transfer Protocol) for the light-weight exchange of files over the Internet. NCSA Mosaic is a World Wide Web browser developed at the National Center for Supercomputing Applications (NCSA). Mosaic's popularity derives, in part, from its ability to communicate using more traditional Internet protocols like FTP, Gopher, WAIS, and NNTP, in addition to http. Mosaic can display text, hypertext links, and inlined graphics directly. When Mosaic encounters a file type it can't handle internally, such as Postscript documents, mpeg movies, sound files, and JPEG images, it uses an external viewer (or player) like Ghostscript to handle the file. Mosaic also includes facilities for exploring the Internet. In other words, Mosaic is an multimedia interface to the Internet. The hypertext documents viewed with Mosaic are written in HTML (HyperText Markup Language), which is a subset of SGML (Standard Generalized Markup Language). All that is needed is just a few more improvements, such as the ability to format tables and mathematics, and a WYSIWYG editor, for HTML to greatly facilitate electronic journals and other publications. NCSA Mosaic for the X Window System is available by anonymous ftp from as source code and binaries for Sun, SGI, IBM RS/6000, DEC Alpha OSF/1, DEC Ultrix, and HP-UX. Questions about NCSA Mosaic should be directed to (X-Windows version), (Macintosh), and (Microsoft Windows). An automatically generated HTML version of the PRG is accessible by WWW as part of the AI-related FAQs Mosaic page. The URL for this resource is The direct URL for the PRG is The remainder of this section lists WWW resources of interest to Prolog and logic programming researchers, students, and practitioners. Constraints: The newsgroup comp.constraints has an ftp archive and WWW home page: Logic Programming: Jonathan Bowen <> [Logic Programming at IBM Research] Peter Reintjes <> ["Issues in Implementing Logic Languages" -- overview of state-of-art in Prolog implementation.] Peter Van Roy <> [Table of Contents from Conferences and Journals in the fields of database systems and logic programming.] Michael Ley <ley@nigra.Uni-Trier.DE> Ken Bowen <> Abstract Interpretation for LP Bibliography: 200 entries so far. Marc-Michel Corsini <>
Subject: [1-16] Prolog Job Postings The PROLOG-JOBS mailing list exists to help programmers find Prolog programming positions, and to help companies with Prolog programming positions find capable Prolog programmers. (Prolog here means Prolog-like languages, including logic programming languages.) Material appropriate for the list includes Prolog job announcements and should be sent to Resumes should NOT be sent to the list. [Note: The 'ai+' part of the mailing list name is used for directing submissions to the appropriate mail-server. The list is NOT restricted to AI-related Prolog jobs -- all Prolog job announcements are welcome.] As a matter of policy, the contents of this mailing list is considered confidential and will not be disclosed to anybody. To subscribe, send a message to with subscribe prolog-jobs <First Name> <Last Name>, <Affiliation/Organization> in the message body. (If your mailer objects to the "+", send subscription requests to "ai+query", job announcements to "ai+prolog-jobs", etc.) For help on using the query server, send mail to with help in the message body. Job postings sent to the list are automatically archived in If you have any other questions, please send them to
Subject: [1-17] Is Prolog really used in Windows NT? Yes. For more information, see Dennis Merritt, "Extending C with Prolog", Dr Dobb's Journal, August 1994, pages 78-82 and 102, 104. D. Hovel, "Small Prolog and Windows NT Networking", Dr Dobb's Journal, August 1994, page 80.
Subject: [1-18] History of Prolog Van Roy, Peter, "1983-1993: The Wonder Years of Sequential Prolog Implementation," DEC Paris Research Laboratory, Research Report 36, December 1993. Kowalski, Robert A., "The Early Years of Logic Programming", CACM, January 1988, pages 38-43. Cohen, Jacques, "A View of the origins and development of Prolog", CACM, January 1988, pages 26-36.
Subject: [1-19] The ISO Standard for Prolog and other Prolog standards The ISO standard for Prolog is ISO/IEC 13211-1:1995. Copies can be purchased from national standards bodies (e.g. ANSI, AFNOR, DIN). It defines the core features of Prolog: part 2, in preparation, will define modules. ISO does not currently make standards available by anonymous FTP, but the 1993 draft ISO standard for Prolog is available by anonymous FTP from [] An unofficial summary of the ISO Prolog standard is available from the same location as isoprolog.tex or Send mail to Michael Covington <> for more information about his summary of the standard. A PostScript version of the August 1995 draft for Part 2 is available from For more information about the ISO Prolog standardzation, write to Roger Scowen, ISO/IEC JTC1 SC22 WG17 (Prolog) convener, 9 Birchwood Grove, HAMPTON, Middlesex TW12 3DU, UNITED KINGDOM, phone +44-181-979-7429, fax +44-181-287-3810, or, preferably, send email to Richard O'Keefe's 1984 Prolog standard draft is available by anonymous FTP from
Subject: [1-A] Acknowledgements The original version of this guide (Version 0.6, Dec 11, 1991) was compiled by Dag Wahlberg, Uppsala University, Sweden <>, and published in the 5(1) issue of the ALP Newsletter (February 1992). Other people who helped with the compilation include Chris Moss <>, Mats Carlsson, SICS <>, Michael A. Covington <>, Jocelyn Paine <>, Per G. Bilse, PDC <>, David Cohen, BIM Systems Inc <>, Mark Korsloot <>, and David W. Talmage <>. Thanks also to Jamie Andrews <>. ---------------------------------------------------------------- ;;; *EOF*

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