Epistemic Consistency in Knowledge-Based Systems

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Today I was informed that my extended abstract, “Epistemic Consistency in Knowledge-Based Systems”, has been accepted for presentation at PT-AI 2017 in Leeds in November. The text of the extended abstract is below.  The copy-paste job I’ve done here loses all the italics, etc.; the proper version is at:

http://sussex.ac.uk/Users/ronc/papers/pt-ai-2017-abstract.pdf

Comments welcome, especially to similar work, papers I should cite, etc.


Epistemic Consistency in Knowledge-Based Systems (extended abstract)

Ron Chrisley
Centre for Cognitive Science,
Sackler Centre for Consciousness Science, and Department of Informatics
University of Sussex, Falmer, United Kingdom ronc@sussex.ac.uk

1 Introduction

One common way of conceiving the knowledge-based systems approach to AI is as the attempt to give an artificial agent knowledge that P by putting a (typically lin- guaform) representation that means P into an epistemically privileged database (the agent’s knowledge base). That is, the approach typically assumes, either explicitly or implicitly, that the architecture of a knowledge-based system (including initial knowledge base, rules of inference, and perception/action systems) is such that the following sufficiency principle should be respected:

  • Knowledge Representation Sufficiency Principle (KRS Principle): if a sen- tence that means P is in the knowledge base of a KBS, then the KBS knows that P.

The KRS Principle is so strong that, although it might be able to be respected by KBSs that deal exclusively with a priori matters (e.g., theorem provers), most if not all empirical KBSs will, at least some of the time, fail to meet it. Nevertheless, it remains an ideal toward which KBS design might be thought to strive.

Accordingly, it is commonly acknowledged that knowledge bases for KBSs should be consistent, since classical rules of inference permit the addition of any sentence to an inconsistent KB. Accordingly, much effort has been spent on devis- ing tractable ways to ensure consistency or otherwise prevent inferential explosion.

2 Propositional epistemic consistency

However, it has not been appreciated that for certain kinds of KBSs, a further con- straint, which I call propositional epistemic consistency, must be met. To explain this constraint, some notions must be defined:

  • An epistemic KBS is one that can represent propositions attributing propositional knowledge to subjects (such as that expressed by “Dave knows the mission is a failure”).

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