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Foundation ::
Artificial Intelligence and Expert Systems ::
DEMAID
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DEMAID
A Design Manager's Aid for Intelligent Decomposition
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Moderators:
Adopt This Application!
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SOURCE CODE AVAILABLE
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Many engineering systems are large and multi-disciplinary. Before the design
of new complex systems such as large space platforms can begin, the possible
interactions among subsystems and their parts must be determined. Once this
is completed the proposed system can be decomposed to identify its
hierarchical structure.
DeMAID (A Design Manager's Aid for Intelligent
Decomposition) is a knowledge-based system for ordering the sequence of
modules and identifying a possible multilevel structure for the design
problem. DeMAID displays the modules in an N x N matrix format (called a
design structure matrix) where a module is any process that requires input
and generates an output. (Modules which generate an output but do not
require an input, such as an initialization process, are also acceptable.)
Although DeMAID requires an investment of time to generate and refine the
list of modules for input, it could save a considerable amount of money and
time in the total design process, particularly in new design problems where
the ordering of the modules has not been defined.
The decomposition of a complex design system into subsystems requires the
judgement of the design manager. DeMAID reorders and groups the modules
based on the links (interactions) among the modules, helping the design
manager make decomposition decisions early in the design cycle. The modules
are grouped into circuits (the subsystems) and displayed in an N x N matrix
format. Feedback links, which indicate an iterative process, are minimized
and only occur within a subsystem. Since there are no feedback links among
the circuits, the circuits can be displayed in a multilevel format. Thus, a
large amount of information is reduced to one or two displays which are
stored for later retrieval and modification. The design manager and leaders
of the design teams then have a visual display of the design problem and the
intricate interactions among the different modules.
The design manager could save a substantial amount of time if circuits on
the same level of the multilevel structure are executed in parallel. DeMAID
estimates the time savings based on the number of available processors. In
addition to decomposing the system into subsystems, DeMAID examines the
dependencies of a problem with independent variables and dependant
functions. A dependency matrix is created to show the relationship.
DeMAID is based on knowledge base techniques to provide flexibility and ease
in adding new capabilities. Although DeMAID was originally written for
design problems, it has proven to be very general in solving any problem
which contains modules (processes) which take an input and generate an
output. For example, one group is applying DeMAID to gain understanding of
the data flow of a very large computer program. In this example, the modules
are the subroutines of the program.
The design manager begins the design of a system by determining the level of
modules which need to be ordered. The level is the "granularity" of the
problem. For example, the design manager may wish to examine disciplines (a
coarse model), analysis programs, or the data level (a fine model). Once the system is divided into these modules, each module's input
and output is determined, creating a data file for input to the main
program.
DeMAID is executed through a system of menus. The user has the
choice to plan, schedule, display the N x N matrix, display the multilevel
organization, or examine the dependency matrix. The main program calls a
subroutine which reads a rule file and a data file, asserts facts into the
knowledge base, and executes the inference engine of the artificial
intelligence/expert systems program, CLIPS (C Language Integrated Production
System). To determine the effects of changes in the design process, DeMAID
includes a trace effects feature. There are two methods available to trace
the effects of a change in the design process. The first method traces
forward through the outputs to determine the effects of an output with
respect to a change in a particular input. The second method traces backward
to determine what modules must be re-executed if the output of a module must
be recomputed.
DeMAID carries the NASA case number LAR-14793. It was originally released as part of the NASA COSMIC collection.
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