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Search & Retrieval

Boolean Search

Boolean search is a query style that combines terms with operators like AND, OR, and NOT to control inclusion and exclusion with high precision.

Also known as: Boolean query, Boolean retrieval, AND/OR/NOT search

Definition

Boolean search is a way of expressing exact constraints using logical operators such as AND, OR, and NOT (often combined with parentheses and quotes). It is commonly used in full-text systems to increase precision and reduce noise.

Why it matters

  • Precision: exclude common false positives (e.g., “tax credit” NOT “VAT”).
  • Auditability: the query clearly describes why a document matches.
  • Power users: legal and research users often expect Boolean control.
  • Deterministic behavior: helpful when you need repeatable results.

How it works

(termA AND termB) OR ("exact phrase") AND NOT termC

Operator support varies by engine (case sensitivity, default operators, phrase rules), so query understanding and documentation matter.

Practical example

("withholding tax" OR "dividend tax") AND Belgium AND NOT "US treaty" can narrow results to the exact jurisdiction and topic, excluding an unwanted subtopic.

Common questions

Q: Does Boolean search replace ranking?

A: No. Boolean logic selects a candidate set; ranking still decides which candidates appear first.

Q: Why do my operators behave unexpectedly?

A: Many engines apply implicit operators, stopword removal, or special parsing rules. Consistent query parsing is part of good query understanding.

References

Manning, Raghavan & Schütze (2008), Introduction to Information Retrieval.