# Predicate Logic in Artificial Intelligence

## Predicate Logic:

Every complete sentence contains two parts –
Subject: The subject is what or whom the sentence is about.

Predicate: It tells something about the subject. sentence involving the predicates that describe the property of objects are denoted by P(x) where
P – The Predicate
x – It is a variable denoting any object.

## Characteristics of Predicate Logic:

1. Logical inferencing is allowed.
2. More accurate KR of facts of the real world.
3. Program designing is its application area.
4. Better theoretical foundation.
5. A predicate with no variable is called a Ground Atom.

### Rules of Predicate calculus symbols:

1. Set of letters (uppercase or lowercase) is allowed.
2. Set of digits (0-9) is allowed.
3. Underscore (_) is allowed.
4. Blanks and non-alphanumeric characters can’t be used.
5. Special characters like \$, *, #, and / are not allowed.

#### Symbols:

1. Predicate Symbols: It denotes relations or functional mapping from the elements of a domain to the values true or false.

2. Function Symbols: It denotes relations defined on a domain.

3. Variable Symbols: Lowercase unsubscribed or subscribed letters like x, y, z, t, u, v, etc. It can assume different values over a given domain.

4. Constants: It is fixed value term. They are individual symbols which are names of objects like 1, 2, 3, etc.

5. Quantifiers: There are two types of Quantifiers:
i. Existential Quantifier (Ǝ): It means for some x or there is no x.
ii. Universal Quantifier (∀): It means for all x.

6. Logical Operators: There are five type of logical operators such as – not(~), and (^), or(v), implication, equivalence.