Metalevel Architecture of RALPH-MEA
The four execution architectures (EA) may
provide conflicting decision choices, requiring some sort of arbitration
scheme. This metalevel layer receives as input the decisions of each EA and
uses its meta-knowledge about the
quality of each EA's performance given fixed computation times. At this
point it begins the meta-reasoning task
of deciding whether to continue deliberation or simply output the best
action choice. The latter occurs when the cost associated with the agent's
limited response time and limited resources outweighs the expected
utility of future computation
Continuing deliberation results in consideration of action
sequences, which is the essence of planning. Although none of the knowledge types contain information about states more
than two time units into the future, the Markov assumption allows concatenation of probabilities
to reason about such states. In other words, the influence diagrams of the
EAs can be re-used with only a change to the initial time. This can be
viewed as advancing a planning window, such that to look one layer
ahead means dropping the oldest layer from consideration. This augmented
structure is called a dynamic influence diagram.
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