An Approach to Complex Event Detection in the Web

ii Acknowledgements First of all, I would like to express my gratitude to my thesis supervisor Prof. José Júlio Alferes, of the New University of Lisbon, for guiding me through the entire research process. I would also like to thank to the professors of CENTRIA for the assistance they provided me during my year at UNL, specially to Prof. for everything they taught me. I am also thankful for the support provided by Prof. Enrico Franconi of the Free University of Bozen-Bolzano during the first year of the masters. I gratefully acknowledge the financial support given by the European Commission through the Erasmus Mundus Program, which made possible the completion of my studies at the Free University of Bolzano and the New University of Lisbon. I would like to say thanks to my friends at UNIBZ, especially to Luciana, Magdalena and Juan for their support and those wonderful moments we spent together. I also thank my friends and colleagues at UNL, in particular Dejan, Jignesh, Freddy and Vivek for their unconditional and valuable help and for sharing with me great moments. I am especially grateful to my parents and brother for their constant support and for being with me all the time, even at the distance. I also thank Prof. Laura Cecchi and Prof. Pablo Filottrani from Argentina, for everything they taught me and for giving me the opportunity to pursue my academic goals. I would also like to say thanks to Ricardo Amador of CENTRIA, whose help and suggestions during the implementation phase of the system were very important. Last but not least, I thank Andrea. This thesis could not have been written in En-glish without her help. iii iv Summary Reactivity, the ability to detect events and react to them accordingly by executing appropriate actions, has long been studied in the field of Active Databases and more recently, in the context of the World Wide Web. A common approach for implementing reactive behaviour and evolution in the Web is the use of reactive languages. Such languages use reactive rules for describing the reactive behaviour of a system and in particular, Event-Condition-Action (ECA) rules. The declarative semantics of such rules specifies that upon event detection, if the system's state satisfies the stated conditions then a group of actions are executed. One of the key aspects in the implementation of reactivity is thus the development of event detectors. These systems …