comp.lang.prolog Frequently Asked Questions

Frequently Asked Questions - comp.lang.prolog

Last-modified: 2008-02-15
Last-changes: Add Planet Prolog

Markus Triska (Mar. 2 2007 - ... )

Remko Troncon (Jan. 6 2002 - Mar. 2 2007)

Dirk-Jan Faber (Feb. 1 1999 - Jan. 6 2002)

Jamie Andrews (Aug 26 1992 - Oct. 16 1997)

General Information: This article contains the answers to some
Frequently Asked Questions (FAQ) often seen in
news://comp.lang.prolog/. It is posted (twice a month, currently on
the 2nd and 16th) to help reduce volume in this newsgroup and to
provide hard-to-find information of general interest.

The World Wide Web URL for this FAQ is:

Questions about the FAQ and updates ought to be submitted to

1. What is the Association for Logic Programming?
2. Where can I get a free Prolog for system X (PC, Mac, Unix or other)?

3. What commercial systems are available? What about systems available
for a price from research institutions?

4. How do I get in touch with my Prolog's users' group, sales
representative, or technical support line?

5. I think language X is better than Prolog. What do you think?
6. What are the recent developments?
7. My Prolog prof assigned me this problem. Can you help me with it?
8. Can you suggest some books on Prolog?
9. Are there any WWW archives of comp.lang.prolog ?
10. How can I get the ISO Prolog standard? Where can I go for more
information about it?

11. How does the WAM (Warren Abstract Machine) work? How do I write a
WAM-based compiler or a WAM emulator?

12. Is there a WWW page on logic programming?
13. Can do I do Internet/WWW programming with Prolog?
14. Is there a WWW page with some tutorials on prolog?
15. How do I edit Prolog code?

1. What is the Association for Logic Programming?

To keep up with the current state of logic programming technology,
readers can join the Association for Logic Programming (ALP) and
receive their Newsletter. For details on how to join or send in
contributions, check or

Sandro Etalle <etalle@xxxxxxxxxxxxx>

The Prolog Resource Guide (v0.6) was printed in issue 5/1 of the
Newsletter (Feb. 1992). This lists information concerning Prolog
Archives, Books, Suppliers, etc. It is now maintained by Mark
Kantrowitz (<Mark.Kantrowitz@xxxxxxxxxxxxxxxxxxxx>), and used to be
posted periodically to news://comp.lang.prolog.

2. Where can I get a free Prolog for system X (PC, Mac, Unix or other)?

The following are anonymous-FTP sites for free Prologs (or related
languages) which are either in the public domain or are "copy-lefted"
(permitted to be copied with some restrictions on commercial use).

(Please note that for extensive development work, users will probably
want a robust interpreter or compiler with good debugging facilities
and a standard syntax, among other things. While public-domain systems
are a valuable service to the community, they do not necessarily have
all these things, and users should weigh carefully what they want to do
against the capabilities and costs of the available systems.)

ALF (Albgebraic Logic Functional language)

+ Platforms: UNIX
+ Available: Unknown
+ E-mail: Rudolf Opalla
+ Info: WAM-based language with narrowing/rewriting

Amzi! Prolog + Logic Server

+ Platforms: Window, Linux and Solaris
+ Available:
+ E-mail: <info@xxxxxxxx>
+ Info: Registration is compulsory, except for the Free
Academic/Personal/Evaluation License.

Aquarius Prolog 1.0

+ Platforms: UNIX
+ Available:
+ Info: High performance, commercial functionality except
debugging and modules.

Argo Prolog v.1.1

+ Platforms: Solaris 1.x and HP-UX 9.x
+ Available: Unknown
+ Contact: Takao Doi <doi@xxxxxxxxx>


+ Platforms: Win32
+ Available:
+ Info: Arity/Prolog32 provides a complete Prolog programming
environment in which you can write, debug, and run Prolog
programs in 32-bit Windows environments (95/98/NT/2000).
Arity/Prolog32 is a powerful, highly optimized, and extended
version of the logic programming language Prolog.
Arity/Prolog32 is a complete compiler and interpreter written
in Prolog, C, and Assembly language and is a superset of
Clocksin and Mellish Prolog.

B-Prolog 4.0

+ Platforms: Win32, Solaris, SunOS, UNIX, FreeBSD and Linux
+ Available:
+ E-mail: Neng-Fa Zhou <support@xxxxxxxxx>
+ Info: Freely available for non-commercial use. For other use a
license is needed.

BinProlog 7.0

+ Platforms: Windows 95/98/NT, Linux and all major Unix
+ Available:
+ E-mail: Paul Tarau <binnetcorp@xxxxxxxxxxxxxx>
+ Info: Download free evaluation copies and see online demos.
Inexpensive Educational licensing available.Has built-in
networking, multi-threading, mobile code and distributed
blackboards. Supports BinNet Internet Programming Tool kit

Brain Aid Prolog (BAP) v1.4

+ Platforms: Transputer systems
+ Available:
+ Info: BAP is a parallel prolog system for Transputer systems.
Available under a Berkely style of copyright.


+ Platforms: Win32, UNIX
+ Available:
+ E-mail: John Pool <j.pool@xxxxxxxx>
+ Info: A Prolog interpreter written in C#. Can easily be
integrated in C# programs. Characteristics: reliable and quite
fast beta version, command line interface, builtin DCG,
XML-predicates, persistent predicates (using Firebird RDBMS),

Ciao 1.4

+ Platforms: Linux, Win32 (95/98/NT), Solaris, SunOS, UNIX in
+ Available:
+ E-mail: Developers <ciao@xxxxxxxxxxxxxxxxxx>, Users
+ Info: Next generation LP/CLP system. Commercial functionality,
but freely available w/source. ISO-Prolog + modules,
networking, multi-threading, clp(r), clp(q), interfaces (Java,
C, tcltk, WWW, databases/ODBC, ...), functions, higher-order,
records, persistence, objects, assertions (types, modes, ...),
source debugger, auto-documenter, static debugger, and more.


+ Platforms: UNIX
+ Available: anonymous FTP from
+ Contact: Daniel Diaz <daniel.diaz@xxxxxxxx>
+ Info: Constraint logic programming over finite domains.
Requires GNU C v.2.4.5 or higher.


+ Platforms: UNIX
+ Available:
+ Contact: Yan Georget <Yan.Georget@xxxxxxxx>
+ Info: Requires GNU C (gcc) version 2.4.5. or higher.


+ Platforms: UNIX
+ Available: E-mail request from Joxan Jaffar
+ Info: Constraint logic programming language, for academic and
research purposes only.

ECLiPSe Constraint Logic Programming System, subsuming Prolog.

+ Platforms: Solaris, Linux, Linux/Alpha, Mac OS X, Windows
+ Available: or
+ Info: ECLiPSe is a Prolog and Constraint Programming platform
with a long history and has been open-sourced in Sept 2006.
+ License: MPL

IF Prolog V5.3

+ Platforms: Windows 95/98/NT/2000/XP, Linux, Solaris, AIX,
HP-UX and other UNIX platforms
+ Available:
+ E-mail: <info@xxxxxxxxxxxxx>
+ Info: IF Prolog is a commercial Prolog system with interfaces
to C/C++, Java, sockets, Windows events and a COM servers. A
graphical debugger allows step-forward, step backward
debugging of Prolog code. A static module concept allows many
additional errors to be detected at compile time. Constraint
Programming (for finite domains, intervals and booleans using
global constraints and linear optimisation).
+ License: Free evaluation copies and inexpensive educational
licensing available.

GNU Prolog

+ Platforms: Many Unixes, Windows, MacOS X
+ Available:
+ E-mail: Daniel Diaz <daniel.diaz@xxxxxxxx>

Jinni 2.27

+ Platforms: Java-based
+ Available:
+ Info: Multi-threaded, Java based Prolog interpreter with
built-in networking, distributed blackboards and mobile code
(inexpensive shareware licensing available).


+ Platforms: Java-based
+ Available:
+ Info: Java Internet Prolog is a cross-platform pure Java 100%
prolog interpreter that supplies Java world with the power of
prolog language and provides prolog language with a technology
to implement new predicates in Java.


+ Platforms: UNIX
+ Available: Anonymous FTP from
+ Info: ICOT Free Software. Concurrent logic programming. Tested
on Sparcs, DEC 7000, Gateway P5-60.
+ Contact: <ifs@xxxxxxxxxx>

LPA Win-Prolog, demo version

+ Platforms: Windows
+ Available: Available from


+ Platforms: Java
+ Available: Available from
+ Info: Proprietory commercial ISO-Prolog Compiler in 100% Java
support for web programming, XML, servlets, applets,
standalones. Free evaluation license.

Modular SB-Prolog (= SB-Prolog version 3.1 plus modules)

+ Platforms: SPARC, DECstation, MIPS, HP 9000 series, Sun 3.
+ Available: Anonymous FTP from
+ Info: Copy-lefted.

Newt Prolog

+ Platforms: Apple MessagePad Newton
+ Available: Currently only beta version available; download and
more information on
+ E-mail: <jlv@xxxxxxxxxxxxxxx>

Open Prolog

+ Platforms: Apple Macintosh
+ Available:
+ E-mail: <brady@xxxxxxxxx>. (Michael Brady).

Poplog Prolog

+ Platforms: Various Unixes, including Sun, Dec Alpha, HP and
many others. Also a Win32 version is available. Sources
available for other combinations.
+ Available: At the Free Poplog Web/FTP site, including full
Mirror sites at
+ E-mail: queries may be posted to news://comp.lang.pop/, or to
<pop-forum@xxxxxxxxxxxxx> or <A.Sloman@xxxxxxxxxxxxx> (Last
+ Info: Robust incremental compiler, part of the multi-language
Poplog system (including Common Lisp, Pop-11 and Standard ML).
Unix, Linux & VMS versions include full support for X window
facilities/Motif. More information at
Licence modelled on XFree86. Can be freely distributed, though
copyright is owned by Sussex University and ISL.


+ Platforms: Unknown
+ Available: On CompuServe in the AIEXPERT forum, interpreter
and examples in PIE2.ZIP, documentation in PIEDOC.ZIP.
+ E-mail: Brent Ruggles <ruggles@xxxxxxxxx>


+ Platforms: UNIX, Linux, beta for MAC
+ Available:
+ E-mail: <pjr@xxxxxxxxxxxxxx>
+ Info: Extended WAM with support for quantifiers and
substitutions, multi-threaded, high-level communication.

Strawberry Prolog

+ Platforms: Windows 95/NT, plans for UNIX and Macintosh
+ Available:
+ E-mail: <dimiter@xxxxxxxxxx>

SWI Prolog

+ Platforms: Binaries for Linux, Windows (NT/2000/XP/Vista) and
Mac OS X (darwin). Sources: ANSI-C, both 32 and 64-bit
machines, compiles on almost all Unix systems and more.
+ Available:,
+ Info: Complete, ISO and Edinburgh standard, common
optimizations, GC including atoms. Portable graphics, multiple
threads, constraints, comprehensive libraries for (semantic)
web programming, Unicode, source-level debugger, advanced
syntax colouring
+ License: LGPL


+ Platforms: Windows 95/98/NT 4.0, plans for Windows 2000, Linux
and Sun Solaris
+ Available:
+ E-mail: <info@xxxxxxxxxxxxxxxx>

UPMAIL Tricia Prolog

+ Platforms: Apple Macintosh
+ Available: Anonymous FTP from;
get README first.
+ Info: UPMAIL is still available, but unsupported.

Visual Prolog

+ Platforms: Win32
+ Available:
+ Info: Includes all the facilities necessary to write mission
critical commercial-grade applications. Fully visual
development environment. Open architecture. Object-oriented.
Built-in database system and ODBC support. Visual Prolog
Personal Edition is available on a freeware license.


+ Platforms: UNIX
+ Available: Anonymous FTP from
+ Info: Compiler which translates Prolog to C via WAM.
Debuggers. Requires GNU C v.2.4.5 or higher.
+ Contact: Daniel Diaz <daniel.diaz@xxxxxxxx>


+ Platforms: Apple Macintosh OS X, 10.2.3+
+ Available:
+ Info: XGP is an open source (GPL) integrated development
environment with user interface and graphics support based on
gprolog and Cocoa under Macintosh OS X.


+ Platforms: Many, including SunOS, Linux and Windows
+ Available:
+ E-mail: <xsb-users@xxxxxxxxxxxxxxxxxxxxx>
+ Info: system with SLG-resolution, HiLog syntax, and
unification factoring.

Yap 4.2.0

+ Platforms: UNIX-based platforms and Windows
+ Available:
+ E-mail: Vitor Santos Costa <vsc@xxxxxxxxx>
+ Info: Yap is entirely written in C and Prolog and should be
portable to most 32-bit and 64-bit Unix based platforms. A
Windows port is also available. Yap4.2 is distributed under
Perl's artistic license and can be freely distributed.

3. What commercial systems are available? What about systems available
for a price from research institutions?

Many commercial systems are listed in the Prolog Resource Guide. The
Resource Guide also lists many systems which are not exactly
"commercial", but available for a price from research instutitions. The
list of such systems was originally compiled by Chris Moss, of Imperial
College. The rest of the Resource Guide was originally compiled by Dag
Wahlberg, of Uppsala University.

The Prolog Resource Guide hasn't been updated lately, but nevertheless
still contains some valuable information. It can be found at

4. How do I get in touch with my Prolog's users' group, sales
representative, or technical support line?

Here are some e-mail addresses of these contacts, listed alphabetically
by company or major product name.

ALS (Applied Logic Systems)

+ Information: <info@xxxxxxx>
+ Sales: <sales@xxxxxxx>
+ Tech support:<support@xxxxxxx>

Amzi! inc.

+ Web site:
+ Information: <info@xxxxxxxx>
+ Sales: <sales@xxxxxxxx>
+ Support: <support@xxxxxxxx>


+ Web site:

BinNet Corporation

+ Web site:
+ Information: <info@xxxxxxxxxxxxxx>
+ Sales: <sales@xxxxxxxxxxxxxx>
+ Tech support:<support@xxxxxxxxxxxxxx>

Ciao, PiLLoW, WebDB, etc.

+ Web site:
+ Users' group: <ciao-users@xxxxxxxxxxxxxxxxxx>
+ Information: <ciao@xxxxxxxxxxxxxxxxxx>
+ Tech support: <ciao-bugs@xxxxxxxxxxxxxxxxxx>


+ Web site:
+ Information: <info@xxxxxxxxxxx> (or .fr)
+ Tech Support: <support@xxxxxxxxxxx> (or .fr)


+ Web site:
+ Users' group: <eclipse-users@xxxxxxxxxxxxxxxxxxxxxxxxx>
+ Information: <eclipse-request@xxxxxxxxxxxxxxxxxxxxxxxxx>
+ Tech support: <eclipse-bugs@xxxxxxxxxxxxxxxxxxxxxxxxx>

Expert Systems Ltd. (Prolog-2)

+ Sales: <sales@xxxxxxxxxxxxxxxxxx>
+ Support: <support@xxxxxxxxxxxxxxxxxx>
+ Users' group: <prolog2-request@xxxxxxxxxxxxxxx>

GNU Prolog

+ Web site:
+ Users' group: <users-prolog-request@xxxxxxx>
+ Bug reports: <bug-prolog@xxxxxxx>


+ Web site:
+ Sales: <sales@xxxxxxxxx>
+ Tech support: <support@xxxxxxxxx>


+ Formerly BIM ProLog

PDC Prolog

+ PDC Prolog is the succesor to Turbo Prolog and the predecessor
to Visual Prolog.

ProLog by BIM

+ Currently MasterProLog


+ Web site:
+ Mailing list: see
+ Sales: <qpsales@xxxxxxx>
+ Tech support: <qpsupport@xxxxxxx>


+ Web page:
+ Mailing list: see
+ Sales: <sicstus-request@xxxxxxx>
+ Tech support: <sicstus-support@xxxxxxx>

Trinc / Trinc-Prolog

+ Information: <info@xxxxxxxxxxxxxxxx>
+ Sales: <sales@xxxxxxxxxxxxxxxx>
+ Support: <support@xxxxxxxxxxxxxxxx>

Turbo Prolog

+ Turbo Prolog is the predecessor of PDC Prolog (see above).

Visual Prolog

+ Web site:
+ Information: <sales@xxxxxx> (or <sales@xxxxxxxxxxxxxxxxx>)
+ Sales: <sales@xxxxxx> (or <sales@xxxxxxxxxxxxxxxxx>)
+ Tech support: <support@xxxxxx> (or

5. I think language X is better than Prolog. What do you think?

These debates rarely result in any productive discussion. To some
extent, one's favourite language is based on irrational ideology.

However, many people now agree that different languages are good for
different things. Prolog seems to be good for problems in which logic
is intimately involved, or whose solutions have a succinct logical
characterization. Like other interactive, symbolic languages, Prolog is
also good for rapid prototyping.

Also, note that there are many different "Prologs" and other logic
programming languages available, all with different capabilities.

6. What are the recent developments?

There are some languages in development which do not have Prolog
syntax, but do subsume and generalize Prolog's logic programming


+ Web site:

The Mozart Consortium:

+ Web site:
+ Users' group: <users-request@xxxxxxxxxxxxx>
+ Tech support: <users@xxxxxxxxxxxxx>

Some other languages bring new developments while also supporting
Prolog syntax and functionality as an option:


+ Web site:
+ Users' group: <ciao-users@xxxxxxxxxxxxxxxxxx>
+ Information: <ciao@xxxxxxxxxxxxxxxxxx>
+ Tech support: <ciao-bugs@xxxxxxxxxxxxxxxxxx>


+ Web site:
+ E-mail: Paulo Moura <pmoura@xxxxxxxxxxx>
+ Info: Open source object-oriented extension to Prolog
compatible with most Prolog compilers.

7. My Prolog prof assigned me this problem. Can you help me with it?

If your instructor assigned it to you, he or she probably wanted you to
do it yourself. If it's an introductory Prolog course, your question
might be elementary to most readers, so it might be a waste of network
resources to ask it. Please ask your instructor, a friend, a teaching
assistant, or a local newsgroup for help first.

That being said, there are news://comp.lang.prolog/ readers who would
be glad to help people making a legitimate attempt to learn Prolog.

8. Can you suggest some books on Prolog?

The Prolog Resource Guide (see above) contains a listing of Prolog
books. It is maintained by Mark Kantrowitz
(<Mark.Kantrowitz@xxxxxxxxxxxxxxxxxxxx>), and posted periodically on

Here are some of the most popular books on Prolog.


+ "Programming In Prolog". William F. Clocksin and Christopher
S. Mellish. Springer-Verlag, 2003 (5th ed).
+ "Prolog Programming for Artificial Intelligence". Ivan Bratko.
Addison-Wesley, 2001 (3rd ed).


+ "The Art of Prolog: Advanced Programming Techniques". Leon
Sterling and Ehud Shapiro. MIT Press, 1994 (2nd ed).
+ "The Craft of Prolog". Richard A. O'Keefe. MIT Press, 1990.

Logic programming theory

+ "Foundations of Logic Programming". John Lloyd.
Springer-Verlag, 1988 (2nd ed).
+ "Logic, Programming and Prolog". Ulf Nilsson and Jan
Maluszynski. Originally published by John Wiley & Sons Ltd
(2nd ed. 1995) but now available without charge from

Expert Systems

+ "Building Expert Systems in Prolog". Dennis Merritt.
Springer-Verlag, 1989. HTML & PDF versions available from

9. Are there any WWW archives of comp.lang.prolog ?

Yes, there are: Google Groups has archives of news://comp.lang.prolog/.
They can be found at

10. How can I get the ISO Prolog standard? Where can I go for more
information about it?

The standard is described in "Prolog: The Standard (Reference manual)",
P. Deransart, A. Ed-Dbali, L. Cervoni, Springer Verlag (1996). Extra
information can be found on
olog/doc/standard/ contains the December 1991 draft, the March 1993
draft, Richard O'Keefe's 1984 Prolog standard draft, and Michael
Covington's summary of the standard. Note that no one at that site can
answer any questions about the standard; it is just an FTP site for the
standard in the USA.

For more information about the ISO Prolog standard, contact:

Roger Scowen
ISO/IEC JTC1 SC22 WG17 (Prolog) convener,
DITC/93, National Physical Laboratory
TEDDINGTON, Middlesex TW11 0LW
Tel: +44 81 943 6956
Fax: +44 81 977 7091
E-mail: <rss@xxxxxxxxxxxxx>

11. How does the WAM (Warren Abstract Machine) work? How do I write a
WAM-based compiler or a WAM emulator?

Reportedly the best tutorial is Hassan Ait-Kaci's book "Warren's
Abstract Machine: A Tutorial Reconstruction" (MIT Press, 1991). The
book is out of print, and available online at

12. Is there a WWW page on logic programming?

Yes, there is one by Jonathan Bowen; the URL is He invites us to mail him at
<jonathan.bowen@xxxxxxxxx> with any relevant information for inclusion.

A blog aggregator called "Planet Prolog" was created by Tom Schrijvers
and features some Prolog-related blogs. Visit and contact Tom at
<tom.schrijvers+planet@xxxxxxxxxxxxxx> to have your blog added.

13. Can do I do Internet/WWW programming with Prolog?

Prolog is very suitable for this task. Several commercial and free
implementations include special support for it. A page specifically on
this topic (including some tutorials) is maintained at A public-domain library
exists (PiLLoW) for several popular Prolog systems which helps in the
task. See:

14. Is there a WWW page with some tutorials on prolog?

Beginner level:

* Adventure in Prolog:
* On-line guide to Prolog Programming:
* Prolog Programming, A First Course:
* Learn Prolog Now!:

Intermediate to advanced level:


15. How do I edit Prolog code?

Emacs and VIM ship with basic support for Prolog. A much improved Emacs
mode is maintained by Stefan Bruda and available from

Logtalk ships with various editing services for many common editors,
also usable for Prolog.

SWI Prolog has a built-in Emacs clone called PceEmacs. There are also
Emacs definitions that let you evaluate embedded queries: An SWI Prolog
programming environment suitable for schools is available from

A Prolog plug-in for the "Eclipse"-IDE is available from:

A sophisticated integrated editing and teaching environment with
declarative debugging, termination analysis and many visualisations is
available from

A. Acknowledgements

Thank you to all the people who helped put together the first version
of this FAQ, and everyone who has contributed to it over the years.
Special thanks to John Dowding for suggesting a good format for the
list, and to Chris Moss, Dag Wahlberg, and Mark Kantrowitz for their
work on the Prolog Resource Guide.

Special thanks to Jamie Andrews, Dirk-Jan Faber and Remko Troncon, who
have been maintaining and posting the FAQ in the past.