  Although the internal structure of a search engine is fairly complex—comprising, among other components, programs called “spiders” that “crawl” the Web—the user-interface portion of the search process is quite straightforward and can be summarized in terms of two steps: (1) a user enters search term/phrase or “keyword” in a “search box”; and (2) the search engine returns a list of relevant Web “pages” that typically include hyperlinks to the pages listed. Many of the early Web search engines were highly specialized and thus could be viewed as “vertical” (i.e., in current technical parlance regarding search engine technology) in terms of their scope. For example, Ask.com was designed to accept queries in the form of specific questions and thus could be viewed as a vertical search engine. Halavais defines a vertical search engine as one that limits itself “in terms of topic, medium, region, language, or some other set of constraints, covering that area in greater depth.” (In this sense, vertical search engines are far more capable of drilling down into particular topics than expanding out into associated subjects.) A few of the popular search engines that flourished during the early Web period, however, were more general, or “horizontal,” in nature. Alta Vista, for instance, was one of the first search engines to fit into this category. Today, most of the major search engines are horizontal, and Google is arguably the best known horizontal search engine. We should note, however, that vertical search engines still play an important role today. Consider an example where one uses Google, or an alternative horizontal search engine such as Yahoo! or (Microsoft’s) Bing, to locate the Web site for Bates College.  Once the user has successfully accessed the main page on the Bates site  she can then use Bates’ local search facility, a vertical search engine, to retrieve information about faculty and staff who work at that college, or retrieve information about various academic programs and co-curricular activities sponsored by that college, and so forth.  Within that vertical search engine, however, the user cannot retrieve broader information about faculty and academic programs at related colleges and universities or about related topics in general (as they could when using a horizontal search engine).