Based on the notion of sets.

Documents are retrieved only if they satisfy boolean conditions specified in the query.

Does not impose a ranking on retrieval documents.

It follows exact matching approach

George boole devised a system of symbolic logic in which he used three operators such as logic sum, product and difference (+,.,-) to combine statements in difference symbolic form.

Information Retrieval systems allow the users to express their queries by using their operators.

A document is represented as a set of keywords.

I/P: queries written inform of boolean expression of keywords connected by AND, OR and NOT

O/P: Document is relevant or not.

It is popular because of following advantages

It is easy to understand for simple queries.

Clear formalism

It assigns the weight in terms of 'o' and 'i' for matching of term in document whereas

O - represents absence of term in document and I- represent presence of term in document

Every document set has perfect query

AND- every word in document to get a query for it

OR- Every document query to get the set query

Disadvantages:

• Boolean logic is insufficient to capture the richness of language

• All index term have equal weight required for Matching process