Booleanmodell

Booleanmodell (Boolean model) is a retrieval model used in information retrieval and database search. It represents documents and queries using boolean logic, where a document is considered relevant if it exactly satisfies a boolean expression built from terms. Queries are formed from terms using logical operators such as AND, OR, and NOT. The model does not produce a graded relevance score; instead, results are treated as a set of documents that meet the specified criteria.

Indexing typically relies on an inverted index that maps terms to the documents in which they appear. Query evaluation proceeds by performing set operations on the posting lists for the terms involved: intersection for AND, union for OR, and complement for NOT. The final result is the exact set of documents that satisfy the boolean expression.

Strengths and limitations: Advantages include simplicity, interpretability, and precise matching for complex queries, including negations. It allows exact control over which terms must or must not appear. Limitations include lack of ranking, sensitivity to vocabulary and spelling, and the need for user expertise to craft effective queries. It does not account for partial relevance or term weighting, which can lead to poorer recall or precision in practice. In large collections, query evaluation efficiency depends on index design and query structure.

Variants include weighted boolean schemes and proximity extensions that attempt to introduce some ranking or closeness constraints while preserving the boolean core. Some systems use the boolean model as a foundation and apply post-processing ranking to the retrieved set.

Origin and use: The boolean retrieval concept dates to early information retrieval research in the 1960s and 1970s, with formal treatments in later decades. It remains a standard baseline in IR education and is used in some specialized search tasks and database query systems where exact control over matching is required.