The Multi-Agent Logics, Languages, and Organisations Federated Workshops (MALLOW for short), in its second edition this year after the success of MALLOW’007 held in Durham (UK), is a forum for researchers interested in sharing their experiences in agents and multi-agent systems. MALLOW’009 was held at the Educatorio della Provvidenza, in Torino (Italy), from September 7th, 2009 through September 10th, 2009. This volume contains the proceedings of the five workshops, for a total of forty-seven high quality papers, which were selected by the programme committees of the workshops for presentation. Each workshop has an introductory essay, authored by the organizers, which presents the workshop.

The Reasoning Web summer school series is a well-established event, attracting experts from academy and industry as well as PhD students interested in foundational and applicative aspects of the Semantic Web. This volume contains the lecture notes of the fourth edition, that took place in Venice, Italy, in September 2008. This year, the school has been focussed on some important application domains where semantic web techniques proved to be particularly effective or promising in tackling application needs.

Rules and ontologies play a key role in the layered architecture of the Semantic Web, as they are used to ascribe meaning to, and to reason about, data on the Web. While the Ontology Layer of the Semantic Web is quite developed, and the Web Ontology Language (OWL) is a W3C recommendation since a couple of years already, the rules layer is far less developed and an active area of research; a number of initiatives and proposals have been made so far, but no standard as been released yet. Many implementations of rule engines are around which deal with Semantic Web data in one or another way. This article gives a comprehensive, although not exhaustive, overview of such systems, describes their supported languages, and sets them in relation with theoretical approaches for combining rules and ontologies as foreseen in the Semantic Web architecture. In the course of this, we identify desired properties and common features of rule languages and evaluate existing systems against their support. Furthermore, we review technical problems underlying the integration of rules and ontologies, and classify representative proposals for theoretical integration approaches into different categories.