Analyzing Concepts and Measurements of Overlap: A literature Review

Purpose: The study׳s aim is to determine the concepts, methods, and applications of overlap and to describe the differences between the domestic and international studies. Methodology: The documentary method is used in this study to analyze the concepts of overlap and the differences between the domestic and international studies through a literature review. Findings: In the overlap area, title overlap, information resources overlap, and topic overlap, have been reported in measuring the databases overlap. A literature review showed that overlap studies had been carried out for one of the following objectives: Overlap theoretical development, explanation of statistical and sampling methods, comparison of the indexing policy of secondary resources, selection of appropriate databases, determination of proper Web search engine, the establishment of interlibrary cooperation, and drawing the relationships among the sciences. It is recommended to use statistical methods to provide the right and enough information for studies. Finally, one may say that the advent of some terms such as journal overlap, journal article overlaps, and topic overlap is due to the researchers' different views. Thus, the topic overlap is used to investigate the indexing policy of the databases and to draw the relationships between the sciences. Conclusion: Finally, it must be said that theory and practice are intertwined. Therefore, choosing the appropriate method to measure the overlap depends on the research objectives. Value: This theoretical study is worthwhile as the local studies carried out up to now, are only practical ones