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From: finin@PRC.Unisys.COM (Tim Finin)
Newsgroups: comp.ai
Subject: Re: Configuration/Constraints info wanted
Keywords: Beacon Configurator
Message-ID: <15965@burdvax.PRC.Unisys.COM>
Date: 20 Dec 90 16:09:07 GMT
References: <1990Dec20.093442.21947@portia.Stanford.EDU>
Sender: news@PRC.Unisys.COM
Reply-To: finin@prc.unisys.com
Organization: Unisys Center for Advanced Information Technology
Lines: 63

In article <1990Dec20.093442.21947@portia.Stanford.EDU>, liemandt@lindy.stanford.edu (Joe Liemandt) writes:
|> 
|> I am interested in learning more about this area.  Any pointers to
|> articles or books? I have read all about XCON.  
|> ...
|> Are there any other large configuration systems implemented besides
|> XCON?
|> ...

We developed a configuration system for Unisys equipment here at the
Paoli Research Center (now known as the Unisys Center for Advanced
Information Technology).  Here is a brief description.  More
information can be found in:

  David B. Searls and Lewis M. Norton. Logic-based configuration with a
  semantic network.  Journal of Logic Programming, 1988.


BEACON is an expert system developed by CAIT to aid in designing
configurations of computers, or any other complex assemblages.  In
particular, BEACON attempts to ensure that such configurations are:
(1) correct and complete at the time of creation; (2) translated into
correct and complete sets of available components; and (3) based on
timely engineering "product" data and in agreement with system
configuration rules.

The configuration design problem domain is complex, is highly product
dependent, and may change with each product release.  For large or
rapidly changing domains such as this, system developers find it
difficult to cope with the complexity and rate of change of the domain
dependent logic that must be housed in their programs.  With
traditional software, developers simply can't match the pace of change
of the knowledge; the software maintenance effort is too great and
proof of correctness is difficult.  BEACON implements a highly
structured KB using the KNET knowledg representation system.  The
aggregation hierarchy here parallels the physical breakdown of systems
into configurable subsystems and orderable components.  Significant
component attributes are also modeled in KNET on the aggregation
hierarchy; the common (more general) aspects of similar systems,
subsystems, and components are recorded at successively higher levels,
while unique (more specialized) aspects are recorded at successively
lower levels.

KNET also gives modelers the power to define higher level restrictions
on a configuration, through the constraint mechanism.  Constraints can
also provide directions to specialized application programs which work
on a KNET structure, such as KNET's Database Loader which incorporates
catalog-level product information (instance-level facts) into the KB
from an external DB.  The Database Loader permits a clean separation
of volatile data from more stable structural knowledge.

Modeling of KBs for BEACON is performed by experts using the KNET
Browser/Editor.  This tool is used for the construction, navigation,
and editing of the KB, and includes a custom window-based interface.
The actual configurator, used at the time a system is ordered, is an
application program which traverses the KNET model of that system.  It
interactively prompts the user for input as it walks the network,
enforcing all KNET constraints as it proceeds, screening out
irrelevant and invalid information, and presenting only relevant
selections at appropriate times.  The configurator thus tailors its
interaction with the salesperson for each order proposal, minimizing
each session.  It too makes use of a specialized window-based
interface.