Index Versus Full-text Search: A Usability Study of User Preference and Performance

“Information by itself is not valuable unless it is accessible: Value is created by pathfinders through the information” (Grimstead 2001, p. 13). As technical communicators, content developers, or information architects (depending on the title we use to characterize the work we do), we certainly recognize that access to the information we create, regardless of the medium, is an essential tenet of effective technical communication. If our specialty is indexing, we understand that a wellcomposed index is one that matches the thinking process and vocabulary of our users. With books and other print references, such as documentation, the usefulness of the product is frequently dependent on the effectiveness of the index. But does the same hold true when the book is an e-book and the users have access to text-search tools and can quickly search the text for whatever word combination they wish? Publishers who engage in e-publishing are leading the trend that bypasses the indexer in the belief that readers can function just as well without an index when offered software that allows them to do full-text searches instead. This belief is based on the increasing familiarity users have with text-search tools to look up information and the publishers’ desire to better control publishing costs and production schedules. But, as many who have experienced the results of a search know, search engines frequently produce hundreds of “hits,” some of them relevant, many of them not so relevant in the context that the user is looking for. Simple keyword text searching is the type of searching most familiar to most people. Type the desired text string in the dialog box, and the search engine will find every occurrence of the string of characters, regardless of the value or significance to the user. Search engines are most effective for the typical user when there is a single objective answer to a simple query, as, for instance, is the case with a search for a particular book title on Amazon.com. If you know the name of the book or the author, your search is likely to be fruitful. If you know the topic category—usability, for instance—you are also likely to get a list of books that will be of interest. More complex queries, however, are another matter. If, for instance, you are searching the Web for index usability, you might get more than 200,000 hits covering topics such as indexing, usability, and indexes of sites on usability. You may not find any studies of index usability, or you may give up exploring the options after examining the first 10 or 20 items in the results list. As well, the order of the list of hits may have no meaning or usefulness to you, and, to narrow your search, you might need to use the dreaded “advanced search” button, which will likely add to your anxiety if you are like most people who know very little about effective advanced searching techniques such as Boolean logic. In this article, we report on the results of testing two versions of an information product, Usability testing and research: one version, an e-book with an index with the locators hyperlinked to the page reference for each entry; the other version, the same e-book without an index, but with full-text search capabilities. We describe the methodology for testing, the testing results, our conclusions, and implications for future research. Before discussing these issues, however, we summarize the current literature regarding human indexing and information retrieval by machine (search engines).