Online and Electronic Indexes
Although indexing services continue to index scientific literature much as in the past, few any longer compile their indexing into the printed monthly and annual cumulations such as Index Medicus or Chemical Abstracts that once sat in long rows on university library shelves. The database products that have replaced cumulated print indexes nevertheless still depend on controlled vocabulary indexing as a means of achieving acceptable degrees of relevancy in retrieving citations from among millions of abstracts. To eliminate the many marginal “hits” that result from the unmediated keyword searching of large databases, search screens typically allow users to construct their searches by selecting from thesaurus terms or employ built-in mechanisms that map natural language queries to assigned, thesaurus-based indexing terms. Taxonomies designed for the graphic interfaces of the Web have been among the more popular means of providing classified or topical access to document collections, most commonly to consumer health information. However, informal taxonomies classifying articles by topics of general interest to medical students, practitioners, and researchers have also been employed by medical publishers to supplement keyword-based search engines at their journals' websites. Scientific validity and consistency, rather than style, are of primary concern in both database indexing and taxonomy classification. Embedded indexing,15,16 a process whereby the indexer embeds markers in passages of text at which index entries should point, allows index terms to be compiled into both print indexes to be included in the back of a book and electronic indexes in which hyperlinks replace page locators. Embedded indexing, usually available in desktop publishing packages, has been used mostly for technical manuals issued simultaneously in print and electronically and which may be updated frequently. Style considerations are much the same as those for traditional back-of-the-book indexes.