Why would you read this preface? As we start thinking what to write here, we wonder who is going to read these words. Fromourperspective-thatofwritersaddressinganaudienceofreaders-you are most likely Willem-Paul de Roever. Willem: our main motivation in putting together this Festschrift is to honor you on the occasion of your retirement. In terms of scienti?c ancestry, you are a father to two of us, and a grandfather to 1 the third, and you have had a profound impact on our formation as computer scientists.Atthepersonallevel, weknowyouasakind-hearted, generousperson. We are grateful to know...