John Laird

A problem-solving architecture is developed where all appropriate knowledge is brought to bear to control all aspects of problem-solving behavior. Such an architecture allows the creation of completely reflective problem solvers. A specific capability called universal subgoaling is identified that, together with previous work on a universal weak method, makes this possible. With universal subgoaling, subgoals arise whenever there is a difficulty in performing the problem-solving functions. In a subgoal, the problem solver brings its knowledge to bear to reason about and eliminate the difficulty. A set of requirements is identified that must be met by any problem-solving paradigm and architecture that realizes universal subgoaling. An implementation of universal subgoaling within Soar, a production system based on search in a problem space, is then described. Two dimensions of universal sugoaling are provided: (1) Soar creates subgoals whenever difficulties arise in any aspect of problem solving, (2) it is possible to encode the knowledge required to produce the weak methods so that the knowledge is used whenever it is needed. As part of the second demonstration, a useful taxonomy is provided of the weak methods based on the knowledge required to encode the in Soar.