THE XSB LOGIC PROGRAMMING SYSTEM

Besides providing all the functionalities of a Prolog system, XSB includes an optimizing compiler, a module system, list processing libraries, and dynamic loading. Furthermore, it extends Prolog by including implementations of OLDT (tabling) and HiLog terms.

The XSB distribution includes all source code and a user's manual. The system can be compiled using the GNU C compiler, and besides the SGI it has currently been tested on several other platforms, however, porting XSB to any 32-bit machine running Unix, should be straightforward.

The current version of XSB is 1.2.

In the following we briefly describe new features of XSB (that are not provided by other Prolog systems), and finally we give instructions on how to ftp XSB.

OLDT resolution is useful for recursive query computation, allowing programs to terminate correctly in many cases where Prolog does not. Users interested in Parsing, Program Analysis, and memory-resident Deductive Database applications may benefit from XSB.

XSB's OLDT implementation:

• Is incorporated at the emulator level for maximal efficiency. The speed improvement over meta-interpreters written by the XSB group is 2-3 orders of magnitude, with considerable improvements in space as well.
• Evaluates programs with (left-to-right modularly) stratified negation and aggregation.
• Allows for declaration of tabled predicates either automatically by the system or manually by the user.
• Provides standard tabling predicates which can be used to program a number of applications like meta-interpreters for the well-founded semantics (provided as an example program).
• Allows full Prolog functionality in tabled code, including cuts (subject to weak semantic restructions), meta-logical predicates, second-order predicates, etc.

HiLog supports a type of higher-order programming in which predicate symbols can be variable or structured. This allows unification to be performed on the predicate symbols themselves in addition to the arguments of the predicates.

XSB's HiLog implementation:

• Includes a fully integrated HiLog preprocessor. HiLog terms can be used anywhere in XSB, including the interpreter level.
• Provides a number of meta-logical standard predicates for HiLog terms.

Compiler optimizations for HiLog terms are currently under development. How To Obtain XSB

1. Issue FTP command to connect to our ftp server

   ftp sbcs.sunysb.edu or ftp 130.245.1.15

   When asked for Name, respond with "anonymous"

   When asked for Password, respond with your e-mail address

2. Issue the following change directory command to where the XSB system is:

   cd pub/XSB

3. Change transfer mode to binary:

   binary

4. Now retrieve the XSB system:

   get XSB.tar.Z

5. Exit the ftp program:

   quit

6. Now uncompress and untar the files:

   uncompress -c XSB.tar.Z | tar xvf -

   Note that this command uncompresses the files into the current working directory, and creates a directory named XSB.

7. From here on read the README file (in directory XSB) that among other things describes how to install the XSB system.