Library and Information Science

This paper attempts to clarify the structure of the field of information retrieval. Co-citation maps and citation diagrams are used to identify specialties and to trace the development of research on information retrieval. In the first-phase co-citation map, following specialties are identified: 1) information retrieval theories, 2) programming and algorithms, 3) fulltext databases and online database retrieval, 4) user modeling in the context of information retrieval, 5) various data structures for information retrieval systems. The developments of research in each specialties are depicted using citation diagrams. To conduct further analysis, the second-phase co-citation maps, i.e. co-citation maps for another aggregate co-citation data, consists of the documents which highly cocited with those are in the each specialties of the first-phase co-citation map. We also identifies the basic literature of each specialties. We discussed the validity of multi-phased co-citation maps and combination with citation diagrams as methods to clarify the structure of disciplines.