David W. Franke. 1992. A theory of teleology. Doctoral dissertation, Computer Science Department, University of Texas at Austin, May 1992. (Available as TR AI93-201.)


A representation language for teleological descriptions, or descriptions of purpose, is defined. The teleology language, TeD, expresses the descriptions of purpose in terms of design modifications that guarantee the satisfaction of design specifications. These specifications express potential behaviors the designed artifact should or should not exhibit. We define an abstraction relation on behavior and implement model checking and classification algorithms that compute this abstraction relation. The model checking algorithm determines whether or not a behavior satisfies a specification. The classification algorithm provides effective indexing of behaviors and teleological descriptions. We implement an acquisition technique for teleological descriptions and demonstrate how teleological descriptions can subsequently be used in diagnosis, explanation, case-based reasoning, design by analogy, and design reuse.

We demonstrate the behavior language, teleology language, acquisition of teleological descriptions, and application of teleological descriptions in explanation, diagnosis, and design reuse via examples in the thermal, hydraulic, electrical, and mechanical domains. We define additional teleological operators that express purposes like prevent, order, synchronize, maintain, and regulate, demonstrating the ability to represent common human-generated descriptions of purpose in TeD. Expressing the purpose of preventing an undesirable behavior is unique to TeD, and is an example of TeD's ability to express purposes regarding missing behaviors and components removed from a design.

The teleology language developed in this work represents a significant advance over previous work by providing a formal language that 1) is independent of any particular domain of mechanisms or behavior language, 2) can be effectively acquired during the design process, and 3) provides an effective means of classifying and indexing teleological descriptions.

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