XSB 2.4 released

Version 2.4 of XSB, a tabled logic programming and deductive database
system has been released. You can find more information, and download
the system from


Included below are the changes for this release.


Release Notes for Version 2.4



* XSB now permits user programs to register hooks to be called when
an undefined predicate is encountered. This and other (previously
undocumented) hooks are described in the chapter titled Hooks in
Manual Part 1.
* The [1]XMC Model Checking System is now included as a package in
* Local scheduling has been made the default scheduler.
* Uniform interface to various file operations (chdir, isdir,
readable, etc.) through the predicate path_sysop/2 and
path_sysop/3 (in module file_io). See Manual, Part 2 (Script
* New string matching function, string_match/4, which extends
str_sub/3. (string_match/4 doesn't do pattern matching - use the
regmatch package for that). See Manual, Part 2, (String


* Fixed subsumption bug prompted by certain uses of functors and
lists. The bug appeared as an inability to unify a (falsely
identified) answer with an answer template.

Backward Incompatibility

* The meaning of argument 3 in predicate str_sub/3 has changed. It
still represents the position of the substring match. However,
offsets now start from 0, like other string functions, instead of


This release of XSB contains an alpha release of a completely
redesigned and reimplemented FLORA system (now called FLORA-2). Here
is an incomplete list of the main new features of the system:
* Integrates F-logic, HiLog, and Transaction Logic into one coherent
* Provides a new, flexible module system
* Better equality maintenance and support for inheritance
* Support for preprocessing
* Many more enhancements

We recommend that Flora users should start using Flora-2, as the
previous version of Flora is no longer maintained and will eventually
be deprecated.


1. http://www.cs.sunysb.edu/~lmc/

Posted by Luis Castro 2001-07-13

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