Block Diagrams for Modeling and Design
Professor Edward A. Lee
UC Berkeley
Friday, October 24th, 1997
Hogan Room, 531 Cory Hall
4:00-5:00 p.m.
Abstract:
Visual depictions of electronic systems have always held a strong
human appeal, making them extremely effective in conveying information
about a design. A few attempts to use such depictions to completely
and formally specify systems have succeeded, most notably in circuit
design, where schematic diagrams can capture all of the essential
information needed to implement some systems. Others have failed
dramatically, for example flowcharts for capturing the behavior of
software. Recently, a number of innovative visual formalisms have been
garnering support, including visual dataflow, hierarchical concurrent
finite state machines, and object models. This talk focuses on the
subset of these that are recognizable as "block diagrams." Such
diagrams represent concurrent systems, but there are many possible
concurrency semantics. Formalizing the semantics is essential if these
diagrams are to be used for system specification and design.
This talk explores some of the possible concurrency semantics,
arguing that their strengths and weaknesses make them complementary
rather than competitive, so that no single model is likely to emerge
as a universally useful model. I will also describe some recent
innovations where concurrency models are combined with automata for
sequential control. So-called hybrid systems are a special case of
such combinations.