pumps, and the like in automation and process control. The ability to pack distinct, seemingly unrelated behaviors into a single operating entity seems promising in areas like robotics, self-guided vehicles, and the modeling of biological systems. The combination of reactivity and rich scripts can be applied to information-system management including workflow control, event processing, root-cause analysis, and automated configuration, among others. Finally, the ability to trace events in the context of their respective scenarios, may allow decision-making applications to explain their behavior and facilitate ongoing human validation.

Behavioral programming may also accommodate customization as part of the development cycle, where end-users can enhance, change, or remove functionality of delivered systems (for example, smartphones), by coding or downloading new behaviors without accessing the core product code.

As a general paradigm, behavioral programming is still in its infancy. It has been applied to a relatively small number of projects, and the existing tools are not yet of commercial power. More research and development is needed in expanding implementations in a variety of programming contexts and for larger real-world applications. We should also experiment with the collaboration of multiple development groups, and expand the work on formal verification, synthesis, performance and scalability, automated learning and adaptability, the use of natural language, and enhanced play-in.

We feel that the natural incremental development afforded by behavioral programming could become valuable for novices and seasoned programmers alike. We hope the paradigm, with its current implementations in LSC, Java, and other platforms, contributes to the vision of liberating programming, 16 and that this article will encourage debate about the ideas, as well as further research and development.

acknowledgments

David Harel thanks Werner Damm and
Rami Marelly for the wonderful collab-
orations of 1998–1999 and 2000–2003,
respectively, without which the ideas
described here would not exist. We are
grateful to Shai Arogeti, Yoram Atir,
Michael Bar-Sinai, Daniel Barkan, Dan
Brownstein, Nir Eitan, Michal Gordon,
Amir Kantor, Robby Lampert, Sha-
har Maoz, Yaarit Natan, Amir Nissim,
Yaniv Saar, Avital Sadot, Itai Segall,
Nir Svirsky, Smadar Szekely, Moshe
Vardi, Moshe Weinstock, Guy Wiener,
and Guy Weiss for their valuable com-
ments and contributions throughout
the development of this article and
the ideas behind it. Thanks to Shm-
uel Katz for insights on positioning
behavioral programming relative to
aspect-orientation. We also thank the
anonymous reviewers for their valu-
able suggestions.

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David harel ( [e-mail]) is the William sussman Professorial Chair in the department of Computer science and applied Mathematics at the Weizmann institute of science, rehovot, israel. Assaf Marron ( [e-mail]) is a researcher at the Weizman institute of science, rehovot, israel. Gera Weiss ( [e-mail]) is an assistant professor in the department of Computer science at ben gurion university of the negev, be’er sheva, israel.