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 exampie, consider a relation with information on available restaurants, including their location, price range for one diner, and overall food rating. A Laser 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, which we will have to query, repeatedly for a potentially, large set of candidate objects. In this paper, we steady, 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 arid real web-accessible data.