Tesi di dottorato di Paolo Tasca, matricola 955419 Coordinatore del Dottorato Tutore del dottorando

I would like to mention all the people who contributed to the meandering path leading to this milestone. In chronological order: I would like to thank my mother Maria Luisa and my father Livio who from the very beginning, gave me all the support to successfully accomplish all my PhD activities. I am very grateful to my PhD director Massimo Warglien and my supervisor Paolo Pellizzari for their patience and invaluable advice. Moreover I would like to thank Frank Schweitzer who embarked me at the beginning as a visiting student. He allowed me to benefit greatly from all the past and present friends and colleagues at the Chair of Systems Design. My special gratitude goes to Stefano Battiston for his continuous and dedicated tutoring and for his friendship. Last but not least, I am sincerely thankful to Marilisa Novacco for having been a constant source of love during this demanding period of my life