Dynamic sets for search

The success of the proposed information highway hinges partly on solving the problem of locating useful objects out of the terabytes of data available. Therefore, a wide area data storage system (WADSS) must provide supporl for search. We view search as a directed iterative process; at each stage a query is run on a set of objects to reduce the focus to a more interesting subset. Search through a WADSS differs from search through a (distributed) database in that users are willing to trade consistency for performance. For instance, a user would be satisfied if a query were to miss some relevant objects, include irrelevant ones, or obtain out-of-date objects as long as the objects are returned promptly. Moreover, queries in a WADSS maybe long-running, execute over geographically distant repositories, and may be prematurely aborted by the user. A key question is “What is the meaning of a set in this context?”