Electronic document addressing: Dealing with change

The management of electronic document collections is fundamentally differen t from the management of paper documents. The ephemeral nature of some elec tronic documents means that the document address (i.e., reference details o f the document) can become incorrect some time after coming into use, resul ting in references, such as index entries and hypertext links, failing to c orrectly address the document they describe. A classic case of invalidated references is on the World Wide Web-links that point to a named resource fa il when the domain name, file name, or any other aspect of the addressed re source is changed, resulting in the well-known Error 404. Additionally, the re are other errors which arise from changes to document collections. This paper surveys the strategies used both in World Wide Web software and other hypertext systems for managing the integrity of references and hence the integrity of links. Some strategies are preventative, not permitting er rors to occur; others are corrective, discovering reference errors and some times attempting to correct them; while the last strategy is adaptive, beca use references are calculated on a just-in-time basis, according the curren t state of the document collection.