Logics for Belief Base Updating
Résumé
A database is a device to store and retrieve information. In the terminology of Levesque [Levesque, 1984], a database comes equipped with a querying function ASK and an update function TELL. The query ASK (light-on) means that the database is asked whether it follows from the data contained in it that the light in question is on. The answer is basically ‘yes’ or ‘no’. (There might be more cooperative answers such as a variable substitution à la PROLOG.) In the simplest case light-on ollows from the database just if light-on explicitly appears in it, but in the case of more expressive systems such as logical databases the answering mechanism resorts to deduction.