Epistemic queries in Classic
Levesque showed that the ability to formulate queries that refer explicitly to the knowledge of a knowledge base significantly increases the expressiveness of a query language. He demonstrated also that epistemic queries can be reduced to a sequence of non-epistemic, that is to say, conventional queries. However, this reduction technique relies on the very expressive language of full first-order logic with equality. In this paper we show that epistemic queries as expressions of an extension of the concept language Classic, which is severely limited in expressiveness compared to first-order logic, can nevertheless be reduced to non-epistemic queries in many cases.
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