ALE 2.0: An Attribute Logic Engine

Keywords: constraints.

ALE 2.0, a freeware system written in Prolog by Bob Carpenter and Gerald Penn, integrates phrase structure parsing and constraint logic programming with typed feature structures as terms. This generalizes both the feature structures of PATR-II and the terms of Prolog II to allow type inheritance and appropriateness specifications for features and values. Arbitrary constraints may be attached to types, and types may be declared as having extensional structural identity conditions. 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. With suitable coding, it can also execute several aspects of LFG grammars.

The current system is distributed with a number of sample grammars, including a fairly comprehensive implementation of a head-driven phrase structure grammar for English following (Pollard and Sag 1994: Chapters 1--5, 7, and 8), a small version of the Zebra Puzzle demonstrating the use of ALE for logic puzzles, and the phonological and categorial grammars used as examples in the documentation.

Complete documentation (running to 100 pages, with examples of everything, programming advice, and sample grammars) is available as:

Bob Carpenter and Gerald Penn (1992) ALE 2.0 User's Guide. Carnegie Mellon University Laboratory for Computational Linguistics Technical Report. Pittsburgh.

ALE can be run in either SICStus or Quintus Prolog, and with other compatible compilers. SICStus 2.1 #8 or later is required for dealing with cyclic structures.

The system is available via anonymous FTP from:
ftp://j.gp.cs.cmu.edu/usr1/carp/ftp/ale.tar.Z

If you'd like to be put on the mailing list and be informed of updates and so on, send e-mail to carp@lcl.cmu.edu.

Bob Carpenter and Gerald Penn 
Computational Linguistics Program, Philosophy Dept.
Carnegie Mellon University
Pittsburgh, PA 15213, USA
Tel: 412 268 8043
Fax: 412 268 1440
Email: carp@lcl.cmu.edu,
       penn@lcl.cmu.edu