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S. Russell and E. Wefald (1991). Do the right thing : studies in limited rationality (Chapter 2: Metareasoning Architectures), MIT Press

  author =       "Stuart Russell and Eric Wefald",
  title =        "Do the right thing : studies in limited rationality",
  publisher =    "MIT Press",
  year =         "1991",
  series =       "Artificial intelligence",
  address =      "Cambridge, Mass",

Author of the summary: David Furcy, 1999, dfurcy@cc.gatech.edu

Cite this paper for:


Different types of knowledge are identified which define four possible execution architectures (EA's). After describing both taxonomies of knowledge and EA's, the authors insist on the importance of compilation processes to enable an agent to make the same decisions faster. The main claim is that a bounded optimal agent should be designed using all four types of EA's at both the object-level and metareasoning level. This will enable the agent to learn as fast as possible in complex domains with varying degrees of regularity. In conclusion, metalevel knowledge is NOT a separate kind of knowledge but instead reduces to knowledge about the operation of the object-level decision procedure.

Detailed outline



Why? For efficiency reasons (time constraints) and to choose relevant actions.


Execution Architectures

An execution architecture (EA) produces a decision using some knowledge. Main point: Different kinds of knowledge can be acquired from perception. Thus, there exist several (in fact 4) types of EA's.

Types of knowledge The uncompiled architecture uses knowledge of types A,B,C plus the decision-theoretic (DT) principle to make decisions.

Compilation is the process of producing a more efficient implementation of an input-output mapping by transforming one type of knowledge into another. The "most compiled" architectures are called tropistic agents, i.e. reactive agents using production-like knowledge the conditions of which can be directly matched with sensory inputs.

Examples of homogeneous compilation: A + A -> A or B + B -> B as is done in EBL and with macro-operators.

Examples of heterogeneous compilation: Types of EA's Since complex conditions take space for storage and requires time for matching, approximate compilation can be performed (as in Lazy EBL) to trade off accuracy and efficiency. Approximate productions can fire rapidly (defaults) and be overridden by more precise ones if time permits.

Existing metalevel architectures

Summary author's notes:

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Last modified: Mon Apr 5 09:02:17 EDT 1999