Michael Stal (born 1963 in Munich) is German computer scientist. He received a Ph.D. title from the University of Groningen which appointed him an honorary professorship for software engineering in 2010. Stal is currently working for the corporate technology department of Siemens AG and as a professor at University of Groningen. He is editor-in-chief of the Java programming language magazine . Stal co-authored the book series Pattern-Oriented Software Architecture. Volume 1 ”A System of Patterns” book introduced , classified different categories of Design Patterns, and a method how to use .