Matt,
My advice would be to use either a native JavaBean "publish"
model, or a periodic polling model, but I wouldn't advise
trying to combine both models.
If you want to write a native JavaBean that publishes property
change notifications, you will need some way to get notifications
on the native side...your ability to do this will be governed by
how the native code updates the robot state. If you can modify this
code, you can cause notifications to be published by your bean
whenever a native property gets updated.
In general, there is no way to simply "listen" to a C/C++ struct
for changes, in the absence of explicit signalling methods (POSIX
signals, Win32 events, or what have you).
If you want to use a polling solution, this can easily be accomplished
with Jess (as long as you have no real-time requirements). Simply
use a rule with an extremely low salience and a "match any event"
pattern, e.g. something along these lines:
(defrule poll-robot-state
(declare (salience -1024))
=>
(try
(bind ?state (call ?*RobotInterface* getNativeRobotState))
; assert robot state facts here...then possibly do a
; Thread.sleep?
catch
(call ?ERROR printStackTrace)
)
)
Such a rule will fire pretty much continuously whenever there are
no other pending activations.
Hope this helps.
Chad Loder
Rapid 7, Inc.
http://www.rapid7.com
At Thursday 9/6/2001 04:37 PM -0400, [EMAIL PROTECTED] wrote:
>Hello,
>
>I am working on controlling a robot using Jess to provide the deliberation.
>The robot state (position, velocity, status, etc..) are available through C
>functions. I have made an interface that allows me to access them through
>Java. I am trying to determine the best way to maintain the state of the
>robot in a rule engine. So far, I have tried asserting each property as a
>fact, and then having an update function that is called at the end of each
>rule to retract the existing facts and assert new ones. I also tried using a
>template containing a slot for each property. I haven't tried using a Java
>Bean because I am not that familiar with them, but they seem to be the best
>idea. Here are a few questions I would like input on:
>
>1) Which of these formats seems best?
>2) Is there a way to monitor items in a C struct and keep the correlating
>Bean properties updated?
>3) If that is not possible, how can I run a continous (every few seconds at
>least) polling of the robot to keep my properties updated?
>
>These Properties are not being used for time critical issues (ie. obstacle
>avoidance), but I would like fairly frequent updates so that decisions are
>reasonably timely.
>
>Thanks for any suggestions,
>matt
>
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