Most implementations of the Prolog language are designed to serve a
limited set of use cases. SWI-Prolog is no exception to this rule.
SWI-Prolog positions itself primarily as a Prolog environment for‘programming
in the large’and use cases where it plays a central role in an
application, i.e., where it acts as‘glue’between components.
At the same time, SWI-Prolog aims at providing a productive rapid
prototyping environment. Its orientation towards programming in the
large is backed up by scalability, compiler speed, program structuring
(modules), support for multithreading to accommodate servers, Unicode
and interfaces to a large number of document formats, protocols and
programming languages. Prototyping is facilitated by good development
tools, both for command line usage and for usage with graphical
development tools. Demand loading of predicates from the library and a‘make’facility
avoids the requirement for using declarations and reduces
typing.
SWI-Prolog is traditionally strong in education because it is free
and portable, but also because of its compatibility with textbooks and
its easy-to-use environment.
Note that these positions do not imply that the system cannot be used
with other scenarios. SWI-Prolog is used as an embedded language where
it serves as a small rule subsystem in a large application. It is also
used as a deductive database. In some cases, this is the right choice
because SWI-Prolog has features that are required in the application,
such as threading or Unicode support. In general though, for example:
GNU-Prolog is more suited for embedding because it is small and can
compile to native code; XSB is better for deductive databases because it
provides a mature implementation of tabling including support
for incremental updates and Well Founded Semantics1Sponsored
by Kyndi and with help from the XSB developers Theresa Swift and David
S. Warren, SWI-Prolog now supports many of the XSB features.;
and ECLiPSe is better at constraint handling.
The syntax and set of built-in predicates is based on the ISO
standard
Hodgson,
1998. Most extensions follow the‘Edinburgh tradition’(DEC10
Prolog and C-Prolog) and Quintus Prolog Qui,
1997. The infrastructure for constraint programming is based
on hProlog
Demoen, 2002.
Some libraries are copied from the YAP2http://www.dcc.fc.up.pt/\~{}vsc/Yap/
system. Together with YAP, we developed a portability framework (see
section C). This framework
has been filled for SICStus Prolog, YAP, IF/Prolog and Ciao. SWI-Prolog
version 7 introduces various extensions to the Prolog language (see section
5). The
string data type and its supporting set of built-in predicates
is compatible with ECLiPSe.
