nWorld = assignment of values to attributes / truth values to propositional symbols
A somewhat more transparent
representation is based on attributes or propositions.Here, the representation makes an explicit
commitment
that the world is described
by a set of attributes or (in the binary case) propositional symbols.The knowledge base tells us how these
different symbols interact with each other.Semantically, each possible world that the agent considers is an
assignment of values to these attributes.This more transparent representation gives us a lot more power.For example, using logical inference
techniques we can often conclude that certain propositions must take a
specific truth value, without enumerating the entire space of truth
assignments.
However, propositional
reasoning has its own problems.In
many cases, it requires that we repeat what is basically the same piece of
information many many times.For
example, if we wanted to write down the rules of chess (just those governing
the single-move successor function), we would have to restate the rules for
pawn movement separately for every board position.In fact, this process would require about
10^7 axioms.I can’t write even one of
these axioms down for you, because it would be too long, so let me use a
simpler example, one which will be my running example for most of this talk.