Paper ID 422 Evaluating Top-k Queries over Web-Accessible Databases

A query to a web search engine usually consists of a list of keywords, to which the search engine responds with the best or “top ” k pages for the query. This top-k query model is prevalent over multimedia collections in general, but also over plain relational data for certain applications. For example, consider a relation with information on available restaurants, including their location, price range for one diner, and overall food rating. A user who queries such a relation might simply specify the user’s location and target price range, and expect in return the best 10 restaurants in terms of some combination of proximity to the user, closeness of match to the target price range, and overall food rating. Processing such top-k queries efficiently is challenging for a number of reasons. One critical such reason is that, in many web applications, the relation attributes might not be available other than through external web-accessible form interfaces. For example, our food ratings of choice might be provided by a web site that, given a restaurant name, returns the number of “stars ” for the restaurant according to the site’s critics. To identify the top-10 restaurants for a user query, we will then need to repeatedly query this remote ratings site for a potentially large set of candidate restaurants. In this paper, we study how to process top-k queries efficiently in this setting, where the attributes for which users specify target values might be handled by external, autonomous sources with a variety of access interfaces. We present several algorithms for processing such queries, and evaluate them thoroughly using both synthetic and real web-accessible data.