Formal models of Web queries

We present a new formal model of query and computation on the Web. We focus on two important aspects that distinguish the access to Web data from the access to a standard database system: the navigational nature of the access and the lack of concurrency control. We show that these two issues have si gnificant effects on the computability of queries. To illustrate the ideas and how they can be used in practice for designing appropriate Web query la nguages, we consider a particular query language, the Web calculus, an abst raction and extension of the practical Web query language WebSQL. (C)1998 P ublished by Elsevier Science Ltd. All rights reserved.