This book does not tell a story. Instead, it is about stories. Or rather, in technical terms, it is about scenarios. Scenarios of system behavior. It con centrates on reactive systems, be they software or hardware, or combined computer-embedded systems, including distributed and real-time systems. We propose a different way to program such systems, centered on inter object scenario-based behavior. The book describes a language, two tech niques, and a supporting tool. The language is a rather broad extension of live sequence charts (LSCs), the original version of which was proposed in 1998 by W. Damm and the first-listed author of this book. The first of the two techniques, called play-in, is a convenient way to 'play in' scenario based behavior directly from the system's graphical user interface (QUI). The second technique, play-out, makes it possible to execute, or 'play out', the behavior on the QUI as if it were programmed in a conventional intra object state-based fashion. All this is implemented in full in our tool, the Play-Engine. The book can be viewed as offering improvements in some ofthe phases of known system development life cycles, e.g., requirements capture and anal ysis, prototyping, and testing. However, there is a more radical way to view the book, namely, as proposing an alternative way to program reactivity, which, being based on inter-object scenarios, is a lot closer to how people think about systems and their behavior.
David Harel is the Dean of the Faculty of Mathematics and Computer Science at the Weizmann Institute of Science in Israel. He is also co-founder of I-Logix, Inc., Andover, MA, and of SenseIT Technologies, Ltd. (DigiScents Israel). His research interests are in theoretical computer science (especially computability, automata theory and logics of programs), and in software and systems engineering (especially specification and modeling, object-oriented analysis and design, and visual languages), as well as the aesthetic layout of diagrams, clustering algorithms and the synthesis and communication of smell. He is the inventor of the language of statecharts (1983), was part of the team that designed the Statemate (1984-1987) and Rhapsody (1997) tools, and was co-inventor of LSCs (1998). His work is central to the behavioral aspects of the UML. He devotes part of his time to expository work: In 1984 he delivered a lecture series on Israeli radio, and in 1998 he hosted a series on Israeli television; some of his writing is intended for a general audience (see, for example, Computers Ltd.: What They Really Can't Do , Oxford University Press, September 2000). He has received a number of awards, including ACM's Karlstrom Outstanding Educator Award in 1992, and the 1997 Israeli Prime Minister's Award for Software. His book, Algorithmics: The Spirit of Computing (Addison-Wesley, 1987, 2nd. edn. 1992) was the Spring 1988 Main Selection of the Macmillan Library of Science. He is a Fellow of the ACM and of the IEEE.
