Title: A formal theory of indexical knowledge and action
Abstract: Agents act upon and perceive the world from a particular perspective. It is important to recognize this relativity to perspective if one is not to be overly demanding in specifying what they need to know in order to be able to achieve goals through action. An agent may not know where he is, what time it is, which objects are around him, what the absolute positions of these objects are, and even who he is, and still be able to achieve his goals. This is because the knowledge required is indexical knowledge, knowledge about how one is related to things in one's environment or to events in one's history.
This thesis develops a formal theory of knowledge and that handles the distinction between indexical and objective knowledge and allows a proper specification of the knowledge prerequisites and effects of action. The theory is embodied in a logic. The semantics of knowledge proposed is a natural extension of the standard possible-world semantic scheme. The notion of ability to achieve a goal by doing an action is formalized within the logic; the formalization does not require an agent to know in an absolute sense who he is or what time it is.
We then formalize various domains within the logical system proposed. These examples show how actions can be specified so as to avoid making excessive requirement upon the knowledge of agents, and how such specifications can be used to prove that an agent is able to achieve a goal by doing an if he knows certain facts. We direct a significant part of our formalization efforts at a robotics domain, since this kind of application provides the most intuitive examples of situations where indexical knowledge is sufficient for ability. But we also formalize other domains involving temporal knowledge, knowledge of the phone system, and knowledge of one's position in a data structure. The examples involved show that the notion of indexical knowledge is more abstract than one might first imagine. On the basis of evidence provided by the temporal examples, we provide an argument to the effect that the distinction between indexical and objective knowledge accommodated by our framework is of practical interest and that it cannot be handled within previous theories.
Publication Year: 1992
Publication Date: 1992-01-01
Language: en
Type: article
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Cited By Count: 20
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