Impasse-Driven Processing
An impasse in cognitive architectures is defined to be an inability to
proceed with problem solving because of a lack of knowledge. During
the course of normal problem solving, an agent will perceive the
environment, examine its knowledge and goals, and formulate a
response. However, if it is unable to generate a response,
impasse-driven architectures automatically cast this lack of
knowledge as a subgoal to be resolved, and attempts to find
knowledge relevant to this subgoal. It is possible to again
fail to progress on this subgoal, leading to another impasse
and another subgoal. As more impasses occur in subgoals,
processing becomes a stack of subgoals, with each goal waiting
for its subgoal to resolve its impasse. If the same goal
generates several subgoals over time, the problem solving
trace attains a tree structure.
The ability to automatically generate subgoals improves the
flexibility of the architecture and affords a natural
opportunity to learn.
An example of an architecture which is unable to impasse is
Ralph. Partially
as of result of this limitation, Ralph's only search mechanism
is forward chaining, and it is unable to learn.
The following is a list of architectures that solve problems by resolving impasses:
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