השוואת שיטות

	אופרטורי חיפוש בוליאניים	חיפוש ספרות אפורה
תחום	מיומנויות מחקר	מיומנויות מחקר
משפחה	Process / pipeline	Process / pipeline
שנת המקור	1847 (Boolean algebra); 1960s (database applications)	1990s (formalized in systematic review guidelines)
הוגה השיטה	George Boole and IT information retrieval practitioners	Information specialists and systematic review methodologists (Cochrane Collaboration, Health Technology Assessment)
סוג	Tool	Tool
מקור מכונן	Wilkinson, M. D., Sansone, S. A., Vandervalk, B., & Rocca-Serra, P. (2011). Evaluating information retrieval systems: a guide for researchers. Expert Review of Molecular Diagnostics, 11(2), 181–190.	Rothstein, H. R., & Hopewell, S. (2009). Grey literature. In J. P. Higgins & S. Green (Eds.), Cochrane handbook for systematic reviews of interventions (Version 5.0.2, Chapter 13). The Cochrane Collaboration.
כינויים	Boolean logic, Boolean search, AND OR NOT	grey literature, gray literature, unpublished literature
קשורות	2	3
תקציר	Boolean search operators are logical functions—AND, OR, NOT, and parentheses—used to combine and filter search terms in bibliographic databases, library catalogs, and search engines. Named after mathematician George Boole (1815–1864), Boolean logic has been applied to information retrieval since the 1960s. These operators allow researchers to construct complex, precise searches that retrieve only articles meeting specific combinations of criteria, dramatically improving search efficiency and reducing irrelevant results.	Grey literature comprises documents and data not published through conventional commercial channels—including theses, government reports, clinical trial registries, conference abstracts, organizational policy documents, and working papers. Unlike journal articles, grey literature is not indexed in MEDLINE or Scopus and often lacks peer review. However, it is crucial for systematic reviews because it may contain null or negative findings that are less likely to be published (publication bias). Systematic grey literature searching is now a standard component of evidence synthesis and is recommended by the Cochrane Collaboration, PRISMA, and other methodological guidelines.