|Norvig I 449
Objects/AI research/Norvig/Russell: Physical objects can be viewed as generalized events, in the sense that a physical object is a chunk of space–time. For example, USA can be thought of as an event that began in, say, 1776 as a union of 13 states and is still in progress today as a union of 50. We can describe the changing properties of USA using state fluents, such as Population(USA). A property of the USA that changes every four or eight years, barring mishaps, is its president. One might propose that president(USA) is a logical term that denotes a different object at different times. Unfortunately, this is not possible, because a term denotes exactly one object in a given model structure. (The term President(USA, t) can denote different objects, depending on the value of t, but our ontology keeps time indices separate from fluents.) ((s) Cf. >Four dimensionalism/Philosophical theories).
Norvig I 450
Solution: only possibility is that President(USA) denotes a single object that consists of different people at different times. >Beliefs/AI research, >Objects of thought/Philosophical theories, >Objects of belief/Philosophical theories, >Description logic/AI research._____________Explanation of symbols: Roman numerals indicate the source, arabic numerals indicate the page number. The corresponding books are indicated on the right hand side. ((s)…): Comment by the sender of the contribution. The note [Author1]Vs[Author2] or [Author]Vs[term] is an addition from the Dictionary of Arguments. If a German edition is specified, the page numbers refer to this edition.
Stuart J. Russell
Artificial Intelligence: A Modern Approach Upper Saddle River, NJ 2010