Efficient and effective Web change detection

In this paper we present a new technique for detecting changes in Web documents. The technique is based on a new method to measure the similarity of two documents, that represent the actual and the previous version of the monitored page. The technique has been effectively used to discover changes in selected portions of the original document. The proposed technique has been implemented in the CMW system providing a change monitoring service on the Web. The main features of CMW are the detection of changes on selected portions of web documents and the possibility to express complex queries on the changed information. For instance, a query can require to check if the value of a given stock has increased by more than 10%. Several tests on stock exchange and auction web pages proved the effectiveness of the proposed approach. (C) 2002 Elsevier Science B.V. All rights reserved.