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 significant effects on the computability of queries. To illustrate the ideas and how they can be used in practice for designing appropriate Web query languages, we consider a particular query language, the Web calculus, an abstraction and extension of the practical Web query language WebSQL. c fl1998 Elsevier Science Ltd. All rights reserved Key words: World Wide Web, Web Queries, Query Languages, Computability, Formal Models 1. INTRODUCTION Tools and techniques for retrieving information from the World Wide Web are rapidly being developed 9, 10, 13, 4, 12, 8. Most of these works are based on the metaphor of the Web as a database, in order to carry over and adapt familiar query languages s...