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Case Representation
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Case
Representation
Design episodes are represented in the form of SBF
models. These models are based on the component-substance ontology developed
by Bylander and Chandrasekaran. A case is composed by three parts : problem
specification, solution and explanation. The problem specification comprises
a set of high level functionalities (HLF) and functional specifications
(FS) that the new design must have. The case solution describes the design
structures. The explanation is represented in terms of sequences of
transitions between behavioral states.
High level functionalities are abstract and created
to help the user specifying the design problem. A design problem is a tree
of functionalities, where leaves are functional specifications and the
other nodes in the tree represent high level functionalities. This taxonomy
of functionalities makes the task of specifying the design requirements
more flexible and easy to perform. A functional specification is a schema
that represents the initial behavior state, the final behavior state, a
pointer to the internal causal behavior of the design, inputs from the
external environment and structural constraints.
The design solution is a partonomic hierarchy
of device structures. Each structure can be viewed as a set of connected
sub-structures. Substances can flow through structures. The structure schema
is as follows :
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is-a-part-of : the super structure of the
structure;
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consists-of : the sub-structures of the structure;
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is-a : the class of the structure;
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relations : structural relations with other
structures;
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properties : structure properties;
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functions : the structure primitive functions;
A case explanation is the causal behavior of
the design in terms of as directed acyclic graphs (DAGs). The nodes of
a DAG represent behavioral states and the edges represent state transitions.
A behavioral state can be composed of one or more substance schema’s. A
substance schema characterizes the location, properties, and property values
of a substance. A state transition schema has the following slots :
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using-functions : The primitive component’s
functions that allow the state transition to happen;
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under-condition-relation : structural relations
needed to make the state transition to happen;
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domain-principle : domain principles or laws
responsible for the state transition;
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under-condition-component : component conditions
that must be met;
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under-condition-substance : substance conditions
that must be met;
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under-condition-transition : other state transitions
that are influential to the state transition.
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