We would like to thank those people without whom this book would never have been written. First and foremost are our families and friends, who supported us and bore our (physical or mental) absence while we wrote this book. Next we would like to thank the people in the ETSI task forces who have shaped TTCN-3 and continue to advance the language and its use in many areas. We would also like to thank the European ITEA programme, which has supported the transfer of TTCN-3 technology to European industry through the TT-Medal project. Lastly, we would like to thank the test engineers in our companies with whom we have worked and whose application of TTCN-3 in the real world has contributed much to our TTCN-3 experience.