Operator Construction for Re-usable Planners in Complex Practical Domains

The goal of this paper is to present a generalization of methods used in some manufacturing domains for selection and instantiation of plan operators. We call the generalized method operator construction, because it involves building up a description of an operator from individual pieces of knowledge about the capabilities of the processing equipment in the domain. These pieces of knowledge are organized into a reenement-knowledge hierarchy which directs the process of operator construction. This approach diiers from the standard approach in which an operator template is selected from a pre-enumerated set. Operator templates in traditional frameworks can be viewed as a type of compiled domain knowledge. The reenement-knowledge hierarchy, on the other hand, utilizes knowledge directly to produce operator descriptions. We feel there are a number of advantages to this approach which will make it useful in complex practical domains where many operator descriptions are required. The rst advantage is com-pactness; the knowledge hierarchy can usually be represented more compactly and exibly than the set of operators themselves. A second advantage is maintainability; knowledge for generating operator descriptions for the domain is made explicit, where traditionally this knowledge has been embedded in the planner itself. This makes maintenance and modiications much simpler. This approach has been implemented in a manufacturing planner which has been demonstrated to produce feasible and eecient plans.