On Feb 7, 2007, at 7:30 PM, #NG BOON KIAT# wrote:
I'm currently working on a distributed multi-agent simulation
system that uses JESS for behaviour inference. The behaviours are
stored inside a Protege ontology. For each cycle of the simulation,
each agent has to update the ontology, followed by getting the new
behaviour from the ontology.
Ideally, each computer (node) in the system will control a number
of agents as well as have 1 JESS engine. However, during testing of
the framework, I had to simulate the running of 2 nodes on my
computer. This means having more than 1 JESS engine running at the
same time. The first engine works fine, but when the second engine
tried to make a ontology update, I get errors such as unable to
read/write.
Is there really no way to have more than 1 JESS engine running at
the same time?
Of course there is -- you can create as many instance of the
jess.Rete class as you like, and run them all independently. It says
so in the manual, doesn't it? There's even a simple inter-engine
communication mechanism built into Jess (the function "call-on-engine".)
Here's a tiny program in the Jess language that uses two engines. A
rule is defined in the first engine which, when fired, prints a
message, then defines a rule in a second engine, resets it, and runs
it. When you run this program, first the rule fires in the first
engine, and this causes the rule to fire in the second engine, so
you'll see both messages printed once.
(set-reset-globals FALSE)
(defglobal ?*e2* = (new jess.Rete))
(defrule hello-1
=>
(printout t Hello1 crlf)
(call-on-engine ?*e2* (eval "(defrule hello-1 => (printout t
Hello2 crlf))"))
(call-on-engine ?*e2* (reset))
(call-on-engine ?*e2* (run)))
(reset)
(run)
Whenever you're reporting a problem like this, on the Jess list or
anywhere else, it helps to be much more specific about what *exactly*
you tried, and what *exactly* happened, including the *exact* text of
any messages you receive. I don't know what you tried, but "unable to
read/write" doesn't sound like any message that Jess can produce.
---------------------------------------------------------
Ernest Friedman-Hill
Advanced Software Research Phone: (925) 294-2154
Sandia National Labs FAX: (925) 294-2234
PO Box 969, MS 9012 [EMAIL PROTECTED]
Livermore, CA 94550 http://www.jessrules.com
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