http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
Constraint-based representation and reasoning for computer-aided design
Design can be considered as a constraint satisfaction
problem. The process of designing mechanisms, usually
including conceptual and detail design stages, can be viewed
as establishing and maintaining design constraints.
Conventional computeraided design systems are effective for
the later stage of detail design, but provide less support
for conceptual design. An adequate and unified scheme for
representing and satisfying constraints through different
design stages is the most essential part of a truly effective
design system. This dissertation presents such a scheme as
the basic framework of a constraint-based design system. A
constraint-based and object-oriented representation is
proposed to represent geometric structures which allow
incompletely specified geometric information. This
representation defines all geometric information as
constraint objects and maintains a constraint hierarchy and
dependency hierarchies for the automated reasoning process.
Constraint networks are generated by instantiation and
unification of geometric constraints to represent geometric
models. Geometric constraints are satisfied incrementally by
a general reasoning scheme to create a new design when
existing constraints are changed or new constraints are
generated. The reasoning scheme is a combination of value
propagation and constraint activation techniques for
constraint satisfaction. The propagation process is
performed through propagation methods along with sets of
propagation rules. Each set of the propagation rules is
defined for a particular class of constraints. Heuristic
functions are introduced to improve the performance of the
propagation process. An experimental 2D constraint-based
design system is implemented based on the proposed reasoning
framework. Various simple two-dimensional design examples
are shown to demonstrate different functions of the design
system. Although this dissertation focuses on the
representation and automated reasoning of geometric
constraints, a method for using the same framework to combine
functional design with geometric design is also discussed.
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