John Mylopoulos has made ground-breaking contributions to three areas of computer science: arti?cial intelligence, information systems and software - gineering. His contributions have been celebrated on multiple occasions. First, Misha Missiko? organized a one-day symposium on conceptual modeling on June 17, 2003, inVelden, Austria, tocelebrateJohn's60thbirthday.Second, JohnTsotsos led the organization of a day of celebrations on June 27th, 2009 in Toronto, Canada, on the occasionof John's retirementfrom the Departmentof Computer Science of the University of Toronto. This book grew out of our desire to honor and thank John by presenting him at the Toronto reunion with a volume that re?ects his belief that conceptual modeling is becoming a fundamental skill that will be a necessary tool for all futurecomputerscientists.Thepapersinthis bookarewrittenbyleading?gures in technical areas that intersect with conceptual modeling, as well as by John's closest collaborators.We are pleased to present this collection of papers that we believe are of lasting signi?cance and could also be used to support a course on conceptual modeling. We are extremely grateful to the eminent authors, who have contributed such high-quality material.