Soar Issues Deriving from Knowledge, Memory and Representation

• Uniform Knowledge Representation

  The uniformity of Soar's production system (and subsequently its long-term memory) is one of of the major criticisms of the architecture. In particular, declarative and procedural memory are normally viewed as having distinct structures. A similar distinction is often made between semantic and episodic memory as well.

• Results Highly Dependent Upon Choice of Representation

  This is an issue for all cognitive architectures that use some form of symbolic representation. For Soar, both the efficiency and generality of the results of problem solving are critically dependent upon the choice of representation when the system is first designed.

• Fixed and Immutable Representation

  The choice of representation is not easily changed. In particular, the impenetrability of long-term memory and the permanence of these productions make adapting the representation very difficult.

• Meta-Knowledge

  Achieving meta-knowledge reasoning in Soar is made very difficult by the impenetrability of the productions of long-term memory.

• Average Growth Effect

  The size of the knowledge base causes more than just a consideration of the efficiency of the production matcher. An increase in the number of productions represents a greater resource drain for many of the algorithms underlying the architecture. Thus, there may be a slow-down associated with increasing the knowledge base even when the elaboration phase is actually parallelized. This slow-down with respect to an increase in the size of the knowledge base is known as the average growth effect. Although the average growth effect has not been a particular problem for any Soar systems implemented thus far, it must be considered in relevance to Soar's scalability, especially since the solution to expensive chunks is to generate a indefinitely large number of 'cheap' chunks.

• Organization of Large Bodies of Knowledge

  Soar's management of knowledge is inherently non-modular. Although match-based attention relieves this problem (to some degree) at run-time, the knowledge engineer/system designer must organize this information to make it manageable for human knowledge compilation. This somewhat arbitrary division has repercussions for debugging and maintenance of Soar systems.

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