A la memòria de mon pare que m’inculcà que els llibres són una font immensa de coneixement A la meva mare que em revelà que els llibres són una font de plaer infinit To the memory of my father who inculcated in me that books are an immense source of knowledge To my mother who revealed me that books are a source of infinite pleasure Agraïments i Acknowledgments The first words will be to my parents, sister and brother... Les primeres paraules d’agraiment vull que siguin per la mare i el pare per tota la dedicació que van posar en la meva educació. S’hi van haver d’escarrassar molt per a que m’interesses la lectura i per motivar-me en els estudis!!! Una forta abraçada a la meva germana i al meu germà amb qui tants jocs i baralles hem compartit. I would like to thank my advisor Ramon Sangüesa who introduced me in the field of

Ingcreasingly, data-mining algorithms must deal with databases that continuously grow over time. These algorithms must avoid repeatedly scanning their databases. When database attributes are symbolic, ADtrees have already shown to be efficient structures to store sufficient statistics in main memory and to accelerate the mining process in batch environments. Here we present an efficient method to sequentially update ADtrees that is suitable for incremental environments. 1.