Georg Gottlob, Christoph Koch. Monadic Datalog and the Expressive Power of Languages for Web Information Extraction. In Lucian Popa, editor, Proceedings of the Twenty-first ACM SIGACT-SIGMOD-SIGART Symposium on Principles of Database Systems, June 3-5, Madison, Wisconsin, USA. pages 17-28, ACM, 2002. [doi]
Abstract is missing.