[1-12] What is the Basic Andorra Model and AKL?

The Basic Andorra Model is a way to execute definite clause programs
that allows dependent and-parallelism to be exploited transparently.
It also supports nice programming techniques for search programs.  The
idea is to first reduce all goals that match at most one clause.  When
no such goal exists, any goal (e.g., the left-most) may be chosen.
The BAM was proposed by David H. D. Warren, and his group at Bristol
has developed an AND-OR parallel implementation called Andorra-I,
which also supports full Prolog.  See, for example, 

   Seif Haridi and Per Brand, "Andorra Prolog, an integration of Prolog
   and committed choice languages", in Proceedings of the FGCS 1988,
   ICOT, Tokyo, 1988.

   Vitor Santos Costa, David H. D. Warren, and Rong Yang, "Two papers on
   the Andorra-I engine and preprocessor", in Proceedings of the 8th
   ICLP. MIT Press, 1991.

   Steve Gregory and Rong Yang, "Parallel Constraint Solving in
   Andorra-I", in Proceedings of FGCS'92. ICOT, Tokyo, 1992.

AKL (Andorra Kernel Language) is a concurrent constraint programming
language that supports both Prolog-style programming and committed
choice programming.  Its control of don't-know nondeterminism is based
on the Andorra model, which has been generalised to also deal with
nondeterminism encapsulated in guards and aggregates (such as bagof)
in a concurrent setting. See, for example,

   Sverker Janson and Seif Haridi, "Programming Paradigms of the Andorra
   Kernel Language", in Proceedings of ILPS'91. MIT Press, 1991.

   Torkel Franzen, "Logical Aspects of the Andorra Kernel Language", SICS
   Research Report R91:12, Swedish Institute of Computer Science, 1991.

   Torkel Franzen, Seif Haridi, and Sverker Janson, "An Overview of the
   Andorra Kernel Language", In LNAI (LNCS) 596, Springer-Verlag, 1992.

   Sverker Janson, Johan Montelius, and Seif Haridi, "Ports for Objects
   in Concurrent Logic Programs", in Research Directions in Concurrent
   Object-Oriented Programming, MIT Press, 1993 (forthcoming).

The above papers on AKL are available by anonymous ftp from 
An (as yet non-released) prototype implementation of AKL is available
for research purposes (contact sverker@sics.se). 
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