Robot-generated Web indices such as AltaVista are comprehensive but imprecise; manually generated directories such as Yahoo! are precise but cannot keep up with large, rapidly growing categories such as personal homepages or news stories on the American economy. Thus, if a user is searching for a particular page that is not cataloged in a directory, she is forced to query a web index and manually sift through a large number of responses. Furthermore, if the page is not yet indexed, then the user is stymied. This paper presents Dynamic Reference Sifting -- a novel architecture that attempts to provide both maximally comprehensive coverage and highly precise responses in real time, for specific page categories.
To demonstrate our approach, we describe Ahoy! The Homepage Finder (http://www.cs.washington.edu/research/ahoy), a fielded web service that embodies Dynamic Reference Sifting for the domain of personal homepages. Given a person's name and institution, Ahoy! filters the output of multiple web indices to extract one or two references that are most likely to point to the person's homepage. If it finds no likely candidates, Ahoy! uses knowledge of homepage placement conventions, which it has accumulated from previous experience, to "guess" the URL for the desired homepage. The search process takes 9 seconds on average. On 74% of queries from our primary test sample, Ahoy! finds the target homepage and ranks it as the top reference. 9% of the targets are found by guessing the URL. In comparison, AltaVista can find 58% of the targets and ranks only 23% of these as the top reference.