Semantics

Semantics

The semantics of the operators of propositional calculus can be defined in terms of truth tables.

The meaning of P ∧ Q is defined as “true when P is true and Q is also true.”

The meaning of symbols such as P and Q is arbitrary and could be ignored altogether if we were reasoning about pure logic.

In other words, reasoning about sentences such as P ∨ Q∧ ￢R is possible without considering what P, Q, and R mean.

Because we are using logic as a representational method for artificial intelligence, however, it is often the case that when using propositional logic, the meanings of these symbols are very important.

The beauty of this representation is that it is possible for a computer to reason about them in a very general way, without needing to know much about the real world.

In other words, if we tell a computer, “I like ice cream, and I like chocolate,” it might represent this statement as A ∧ B, which it could then use to reason with, and, as we will see, it can use this to make deductions.