MONTHLY PROGRESS REPORT

CONTRACTOR:           University of California at Berkeley
TITLE:                Open Control Platform
REPORT PERIOD:        5/15/00 - 6/15/00
SPONSOR:              Boeing Subcontract, Air Force Research Laboratory (AFRL)
REPORT PREPARED BY:   Edward A. Lee


1.  Research Status

 Software Architecture
 =====================

At the PI meeting in Albaquerque, we demonstrated hierarchical
heterogeneous modeling and design using Ptolemy II to integrate smart
sensors and motor-drive actuators to control small robots. The
implementation used a publish-and-subscribe fabric (JavaSpaces), a
service discovery fabric (Jini), a discrete-event simulation engine
(the Ptolemy II DE domain), and a dataflow computation engine (the
Ptolemy II SDF domain). The discovery mechanism was used to dynamically
discover the publish and subscribe fabric. We believe that the same
infrastructure can be used to discover other publish-and-subscribe
fabrics, in particular, the OCP. 

A number of issues were raised by this demo with regard to the
semantics of the publish-and-subscribe infrastructure. There are a
number of options in configuring this infrastructure. For instance:

  - Should events have time stamps?
  - Should these time stamps have global significance?
  - Should delivery of events be reliable (with retry if necessary)?
  - Should events always be delivered in the order they are produced?
  - How can we coordinate events from multiple sources?
  - Should synchronous event delivery be supported?
  - How should events from multiple publishers be merged?
  - How should dynamic redirection and resourcing of events be supported?
  - Should the fabric provide persistent state?
  - Should the fabric provide history services?

In view of these questions, the next step is to define a precise
semantics for a publish-and-subscribe fabric for software-enabled
control systems, and to characterize where the OCP build 1 is positioned
with respect to these questions.

The demo builders were Chamberlain Fong, Christopher Hylands, Jie Liu,
Xiaojun Liu, Steve Neuendorffer, Sonia Sachs, and Win Williams.

 OCP
 ===

We have installed the prototype of the OCP provided by Boeing, and
run some simple tests under VxWorks.  The next step is to replace
the use of JavaSpaces with the OCP.


 Meetings
 ========

 - David Shim attended the June 8 and 9 Controls API meeting at the
   Boeing Leadership Center in St. Louis.

 - Several of us attended the PI meeting in Albaquerque, June 12 and 13.