Most documents made available on the World-Wide Web can be considered part of an infostructure --- an information resource database with a specifically designed structure. Infostructures often contain a wide variety of information sources, in the form of interlinked documents at distributed sites, which are maintained by a number of different document owners (usually, but not necessarily, the original document authors). Individual documents may also be shared by multiple infostructures. Since it is rarely static, the content of an infostructure is likely to change over time and may vary from the intended structure. Documents may be moved or deleted, referenced information may change, and hypertext links may be broken. As it grows, an infostructure becomes complex and difficult to maintain. Such maintenance currently relies upon the error logs of each server (often never relayed to the document owners), the complaints of users (often not seen by the actual document maintainers), and pe...