# Propositional Logic Inferences in Artificial Intelligence

## Introduction:

In this tutorial, we are discussing propositional logic interferences in AI. Propositional logic interference is essential to AI (Artificial intelligence) and Computer Science. It is a part of mathematical logic. Propositional is based on the Boolean functions, which make them true or false, and adding logic and reasoning techniques to make them more complete. This logic is very old and widely accepted logic. The propositional logic is formed based on the many Artificial intelligence systems like rule-based systems, expert systems, and natural language processing. This logic is used in planning, decision-making, intelligent management, diagnosis, and problem-solving in various fields like business, health, and education.

## What is Propositional Logic in AI?

Proposals of propositional logic provide ways and means of linking or changing propositions to create complex structures, relationships, and new things. It summarizes all important concepts and gives accurate results in difficult conditions. This logic is an essential part of mathematical logic. The propositional statement is based on a Boolean function that provides true or false output. Now here we give an example of propositional logic in an AI-based module. Now the statement is "All flowers are Rose". This statement can be represented as propositional logic. Let's take this proposition as R. Another statement is "Lotus is a flower"; this statement can be similarly represented as propositional logic. Let's take this proposition as Q. We can represent the logical relationship between P and Q by using logical connectives like "not", "or" and "and".

We can give an example using logical connectives. The proposition is "All flowers are Rose, and Lotus is a flower". We can represent this proposition by the logical connectives, which are given below -

Propositional logic is also used in artificial intelligence to consider propositions' relationships. Here we give some propositions, and we can use the rules of reasoning to get new directions. For example, if we know that R ∧ Q is true, then we also know that R → Q, we can infer that Q → R is also true.

## Write down some features of Propositional Logic interference in AI.

Here we discuss some features of propositional logic interference in AI, which are given in below -

1. Propositional logic is a language that uses logical connective symbols to represent propositions and logical connections to communicate. Symbols used in propositional logic include letters such as p, q, and r, which represent propositions, and logical connectors like ∧ (conjunction), ∨ (disjunction), and ~ (negation) to join propositions.
2. The proposition is a Boolean expression. So, a statement in a proposition can be represented as true or false.
3. Here we use logical connectives like "not", "or" and, "and" to make the proposition statement more complex.
4. Truth tables are also used in propositional logic to represent the truth values.
5. Using propositional logic interference, we can find a new proposition by the existing proposition statement.

## What is the syntax of Propositional Logic in AI?

For propositional logic (PL) to be effective, we must follow the language structure that everyone agrees on, and it must be easy for everyone. The propositional logic language structure consists of simple, indivisible elements interconnected by communication objects. The syntax of propositional logic consists of two main components, which are atomic proposition, and another is the compound proposition.

### 1. Atomic Proposition:

Atomic proposition is an important component of propositional logic. It is a simple statement. So, an atomic proposition statement must be divided into simpler statements. A simple letter or symbols like p, q, r, s, etc represent it. Now we give an example of the atomic proposition, which is given below -

p: The flower is red. q: The hair is black. r: 1+1=2. s: The Moon orbits the Earth.

### 2. Compound Proposition:

The compound proposition is another important component of propositional logic. It is mainly a combination of atomic propositions using logical connectives. A compound proposition statement is not a simple statement like an atomic proposition. The logical connectives are ∧ (conjunction), ∨ (disjunction), and ~ (negation). Now we give an example of the compound proposition, which is given below -

"All flowers are Rose, and Lotus is a flower" is an example of a compound proposition where two atomic propositions are combined using the "and" logical operator.

Sentences, verbs, nouns, pronouns, prepositions, etc., consist of a language. It consists of combinations of words such as Grammar of propositional logic languages follow similar rules. So, now we discuss some statement condition and their syntax in the below table -

Sl. No.Statement ConditionSyntax
1.Complex statement condition which is dividableThe complex statement is solved by coding the connectors in a simple bracket.
2.Simple statement condition which is also undividable. Basically, this type of statement is follows Boolean function which returns true or false.This statement is not a sentence, it represents by an upper-case word or a symbol like A, B, C, P, Q, R and S.
3.Logical operator or logical connectives which connect more than two statement by using the operator.The logical operator is ^ (AND), v (OR), → (Implies), ↔ (bi-conditional), and ¬ (negation or NOT condition).

## Some key points of Propositional logic:

Here we mainly discuss some important features or points of the propositional logic, which are given in below -

1. The proposition is a Boolean expression. It can be either true or false. So, if a statement is always true, then this proposition is known as Tautology.
2. On the other hand, if a statement is always false, then this proposition is known as Contradiction.
3. Mainly statement belongs to the category of the proposition. If the nature of the sentence is a command or question, then this sentence is not a proposition statement. An example of a proposition statement is "All flowers are Rose".

## Discuss logical connectives.

Logical connectors connect two simple assertions or logically express a statement. We can create mixed two statements using logical connectives. Using logical connectives, we can build a compound proposition. There are 5 types of logical connectives which are discussed below -

Sl. No.Logical ConnectivesMeaningSymbolDescription
1.ConjunctionANDP ^ QThe conjunction can join two statements by the AND operator. Here P, Q join with the "AND" operator. Example: Rose is a flower (P). Lotus is a flower (Q). Rose and Lotus are flowers represented by (P ^ Q).
2.DisjunctionORP v QDisjunction can join two statements by the OR operator. Here P, Q join with the "OR" operator. Example: Riya is good in Math (P) and Riya is bad in math (Q). Riya is good or bad in Math (P v Q). Here, two statements cannot be true simultaneously. If one is true, then another is false.
3.NegationNOT¬ PThe negative statement mainly represents negation. If P represents a positive statement, then ¬ P represents a negative statement. Example: She is a good student (P). She is not a good student (¬ P).
4.ImplicationIf……thenP → QIf one sentence is dependent on another statement, then this is called implication. Here Q is dependent upon P, P → Q. If statement P is true, then statement Q is also true, and if P is false, the Q is false. It is mainly unidirectional. Example: If today is a holiday (P), then I will go Shopping (Q), and this statement is represented as P → Q.
5.Bi-conditionalExclusive OrP ⇔ QIf both statements depend on each other, then this is called Bi-conditional. Here P is dependent upon Q, and vice-versa, P ⇔ Q. If the list of conditions and vice versa is true, it is called a biconditional connection. The directions of the condition are P → Q and Q → P. A closed statement is true if and only if all conditions are true.

## Truth Table:

Matches the propositional truth values of all possible combinations of several logical connections. It is based on Boolean logic and propositional calculus. All events with a truth value are recorded in a truth table. In propositional logic, a truth table is a tool for calculating the true value of a composite proposition from the true value of each of the propositions that compose it. Here we build the truth table for three propositions: P, Q, and R. The truth table is given below -

 P Q R P ^ Q P v Q (P ^Q) v R ¬ P P → Q P ⇔ Q True True True True True True False True True True True False True True True False True True True False True False True True False False False True False False False True False False False False False True True False True True True True False False True False False True False True True False False False True False False True True True True False False False False False False True True True

In the above cases, we have three considerations: P, Q, and R. The first column lists all the true values of proposition P, the second column lists all the true values of proposition Q, and the third column lists all the true values of proposition R.

In the fourth column, we have done a conjunction operation between P and Q. Mainly; conjunction is performed "And" operation between P and Q. The value of (P ^ Q) is true when both P and Q are true.

In the fifth column, we have done a disjunction operation between P and Q. Mainly; disjunction is performed "Or" operation between P and Q. The value of (P v Q) is true when one of the values of P or Q is true.

In the sixth column, we have done a conjunction operation between P and Q, then performed a disjunction of R with the result of (P ^ Q). Mainly conjunction is performed "And" operation between P and Q; disjunction is performed "Or" operation between (P ^ Q) and R. The value of ((P ^ Q) v R) is true when all P, Q, and R are true or a Minimum of two values between P, Q, and R.

In the seventh column, we have done the negation operation of P. Mainly; negation is performed "Not" operation of P. The value of (¬ P) is true when the value of P is false, and (¬ P) is false when the value of P is true.

In the eighth column, we have done an implication operation between P and Q. Mainly; the implication is performed when Q is dependent upon P. If statement P is true, then statement Q is also true, and if P is false, the Q is also false.

In the ninth column, we have done a bi-conditional operation between P and Q. Mainly, bi-conditional is performed when P and Q depend on each other. The value of (P ⇔ Q) is true when both the value of P and Q are true or false. If one value is true and another is false, then the value of (P ⇔ Q) represents false.

Using the truth table, we can easily determine the true value of the compound proposition based on its true value.

## What are the disadvantages of propositional logic?

There are some disadvantages or limitations of propositional logic, which are discussed below -

1. Expressive power is limited:

Propositional logic is limited in representing relationships between objects or concepts. It can only display simple Boolean expressions with binary truth values , which can be true or false. This makes it difficult to represent concepts such as objects.

2. Handle quantifier is difficult:

Quantifier object is "all", "some", etc. Propositional logic cannot handle the quantifier. Example: We cannot clearly say "all flowers are rose". This makes it difficult to think about a set of objects.

3. Negation support is poor:

This logic does not provide an easy way to express negation. Here we just opposite the given value to find the negation value. This can make it difficult to Represent the negative messages in propositional logic.

4. Temporal relationship difficult to handle:

In propositional logic, the temporal relationship handle is very difficult between states and events. It cannot represent concepts such as physical significance necessary in many AI applications.

## Conclusion:

So, in this article, we are discussing propositional logic interferences in AI. The propositional logic interference is an essential part of AI. It deals with propositions, truth tables, and logical relationships. The syntax of propositional logic consists of two main components, which are atomic proposition, and another is the compound proposition. Propositional logic has 5 types of logical connectives: conjunction, disjunction, negation, implication, and bi-conditional. Because of its ability to solve complex problems, propositional logic is widely used in business, education, and medicine.