Language Design
The primary effort in this project is the design of a language for
compositionally modeling electromechanical systems. We have also been
involved in some preliminary modeling.
The Hybrid CC Language
We are developing the Hybrid CC language, which is a compositional
modeling language for physical systems. We started with Concurrent
Constraint programming languages, which provide the fine grained
concurrency desirable for compositionality. They are very expressive,
being built on top of arbitrary constraint systems, and are
declarative. Each program is a logical formula, facilitating
reasoning about the models. For more details, see the following papers .
CC programs are monotonic, so absence of information is not detected.
However, for realtime programs, it is necessary to do this to
implement, for example, timeouts. Our first solution was building
Timed CC, but a second superior solution is Default CC, which allows
the expression of default statements in a program. Then we extended
the untimed Default CC over continuous time in a generic way, to get
our hybrid language Hybrid CC. An interpreter has been built for this
language over Sictus Prolog, and can be downloaded from here.
People: Vineet Gupta, Radha Jagadeesan, Vijay Saraswat, Danny
Bobrow. Contact Vineet Gupta for more
information and publications for papers.
Modeling Photocopiers
We are trying to model the paperpath of a simple photocopier, so that
we can use the model for simulation, diagnosis, controller generation,
scheduling, explanation generation, design optimization and other
areas.
Our approach to modeling is based on the following guidelines --
- We exploit features of the physical domain for simplifying the
model, but avoid hardwired implicit assumptions about possible
scenarios, design principles etc.
- We aim at reusable model fragments that can be further specialized
and composed to cover different instances of devices, and various tasks.
We address two important problems --- modeling a device with a
topology changing over time, and finding an appropriate level of
abstraction of modeling that still allows us to determine most of the
interesting features, for instance buckling or tearing of paper
sheets. Currently, our model considers a steady state model for the
system. In steady state, the sum of the forces acting on any component
is zero, as nothing is accelerating. This gives a simple set of
constraints, which are solved to get the velocity of the sheet, and
other interesting characteristics.
People: Vineet Gupta, Vijay Saraswat, Peter Struss, Hao-Chi Wong.
Contact Vineet Gupta for more
information. Papers about the modeling effort
are here.
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Last updated on October 27, 1995.