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Open Access Research article

Boolean versus ranked querying for biomedical systematic reviews

Sarvnaz Karimi1*, Stefan Pohl1, Falk Scholer2, Lawrence Cavedon12 and Justin Zobel1

Author Affiliations

1 NICTA, Dept. of Computer Science and Software Engineering, The University of Melbourne, Melbourne, Victoria 3010, Australia

2 School of Computer Science and Information Technology, RMIT University, Melbourne, Victoria 3001, Australia

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BMC Medical Informatics and Decision Making 2010, 10:58  doi:10.1186/1472-6947-10-58

Published: 12 October 2010



The process of constructing a systematic review, a document that compiles the published evidence pertaining to a specified medical topic, is intensely time-consuming, often taking a team of researchers over a year, with the identification of relevant published research comprising a substantial portion of the effort. The standard paradigm for this information-seeking task is to use Boolean search; however, this leaves the user(s) the requirement of examining every returned result. Further, our experience is that effective Boolean queries for this specific task are extremely difficult to formulate and typically require multiple iterations of refinement before being finalized.


We explore the effectiveness of using ranked retrieval as compared to Boolean querying for the purpose of constructing a systematic review. We conduct a series of experiments involving ranked retrieval, using queries defined methodologically, in an effort to understand the practicalities of incorporating ranked retrieval into the systematic search task.


Our results show that ranked retrieval by itself is not viable for this search task requiring high recall. However, we describe a refinement of the standard Boolean search process and show that ranking within a Boolean result set can improve the overall search performance by providing early indication of the quality of the results, thereby speeding up the iterative query-refinement process.


Outcomes of experiments suggest that an interactive query-development process using a hybrid ranked and Boolean retrieval system has the potential for significant time-savings over the current search process in the systematic reviewing.