Dr Tom Henzinger
UC Berkeley
Friday, November 14th, 1997
Hogan Room, 531 Cory Hall
4:00-5:00 p.m.
Block diagrams can be interpreted in (at least) two radically different ways. In the I/O view, blocks are interpreted as operators that transform inputs into outputs, and lines are interpreted as routing information. By contrast, in the state view, blocks are interpreted as system states or state clusters, and lines are interpreted as state transitions. While the I/O view is data-centric, the state view is control-centric. In the I/O view, concurrency is built-in but operationality is not, and is studied in the theory of determinacy (fixpoints etc.). In the state view, on the other hand, operationality is built-in but concurrency is not; it is introduced by a parallel composition operator and studied in the theory of concurrency. We give a brief overview of the main issues in concurrency theory, including states vs. events, synchronous vs. asynchronous interaction, true concurrency vs. interleaving, linear time vs. branching time.