|Abstract or Summary
- A representation for the process of mechanical design,
along with its computer implementation is presented and
discussed. The representation consists of three
fundamental concepts: design objects, constraints, and
decisions. The design objects are the structures with
which the physical artifacts of the design are described.
A design object consists of a set of attributes that
represent the properties and characteristics of that
object. The values of these attributes are specified by
the constraints of the design.
The constraints specify the values of and relations
between the attributes of the design object. The
conglomeration of design objects and their respective
constraints define the state of the design. The state of
the design can be thought of as a snapshot of the design
taken at any particular time in the design process.
Changes to this state occur through the introduction of
new constraints into the design space.
New constraints are brought into the design by the
application of a design decision. The design decision
process consists of a set of input constraints, an
evaluation performed on those input constraints and the
subsequent generation of one or more new resulting
constraints. These new constraints in turn affect the
attribute values and relations of the design objects,
thereby changing the state of the design.
This representation is capable of storing not only the
final state of a design, but the initial and intermediate
states as well. Maintained also, is the process of change
from one design state to the next. By using this
representation, one can inspect the evolution of design
objects, the propagation and dependencies of the
constraints, and the rationale behind the decisions of the
This representation was developed from data extracted
from mechanical design protocols. These protocols were of
mechanical designers solving original design problems and
consisted of video recordings, verbal transcripts, and the
designer's original drawings.
The representation was implemented in HyperClass, an
object oriented programming environment. The
implementation is capable of generating and displaying
graphical images of the design. The design information
extracted from the protocols can be recorded by the