jason-users Mailing List for jason

Hi Rafael,
thank you a lot for your prompt answer!

On Mon, 20 Sep 2004 10:16:35 +0100
Rafael H Bordini <R.B...@du...> wrote:

> When you use ".send" with "tellHow" as illocutionary force, the 3rd
> argument is expected to be a term in the form of a string that can be
> *parsed* into a plan(exactly as the plans in text source code are parsed
> into the initial plan library). So, at the moment if in plan p1 (with
> triggering event te1(t) and context c1(t)) you know you need to send, to
> ag2, plan p2 (with triggering event te2(t), context c2(t) and body a2(t))
> you can give your agent a plan like this:
>
> p1 ->
> te1(t) :
>   c1(y) <-
>     .send(ag2,tellHow,"p2 -> te2(t) : c2(t) <- a2(t).").
>
> This should already run in Jason, hopefully with no problems.

I've tried your plan but it doesn't seem to work due to a parser problem;
what I've done has been to construct two silly agents with the following
definitions:

ag1.asl ===========================================================

p1 ->
+start(game) : true
<- .send(ag2, tellHow, "p3 -> +play(game) : true <- .print(OK).").

ag2.asl ===========================================================

p2 -> +do(nothing) : true <- true.

...and a standard environment that adds "start(game)" as initial percept to
both agents. Here below there is the output of the execution of such
agents...

dmr:nicetas:0:~/job/newnewtest$ ./Test.sh
Creating environment TestEnv
Creating agent ag1 (1/1) from jason.CentralisedAgArch
as2j: AgentSpeak program parsed successfully!
setting option from {verbose=1}
Creating agent ag2 (1/1) from jason.CentralisedAgArch
as2j: AgentSpeak program parsed successfully!
setting option from {verbose=1}
Error parsing literal "p3 -> +play(game) : true <- .print(OK)."
parser.ParseException: Encountered "\"p3 -> +play(game) : true <-
.print(OK).\"" at line 1, column 1. Was expecting one of:
    "~" ...
    <ATOM> ...
   
        at parser.as2j.generateParseException(as2j.java:1502)
        at parser.as2j.jj_consume_token(as2j.java:1382)
        at parser.as2j.l(as2j.java:223)
        at jason.Literal.parseL(Literal.java:45)
        at stdlib.send.execute(send.java:43)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:
39)        at
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorIm
pl.java:25)        at java.lang.reflect.Method.invoke(Method.java:324)
        at jason.InternalAction.run(InternalAction.java:61)
        at jason.TransitionSystem.applyExecInt(TransitionSystem.java:279)
        at
jason.TransitionSystem.applySemanticRule(TransitionSystem.java:92)      
at jason.TransitionSystem.reasoningCycle(TransitionSystem.java:494)      
at jason.CentralisedAgArch.run(CentralisedAgArch.java:78)
java.lang.reflect.InvocationTargetException        at
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)        at
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:
39)        at
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorIm
pl.java:25)        at java.lang.reflect.Method.invoke(Method.java:324)
        at jason.InternalAction.run(InternalAction.java:61)
        at jason.TransitionSystem.applyExecInt(TransitionSystem.java:279)
        at
jason.TransitionSystem.applySemanticRule(TransitionSystem.java:92)      
at jason.TransitionSystem.reasoningCycle(TransitionSystem.java:494)      
at jason.CentralisedAgArch.run(CentralisedAgArch.java:78) Caused by:
java.lang.NullPointerException        at
jason.Unifier.apply(Unifier.java:38)        at
stdlib.send.execute(send.java:47)        ... 9 more

In the meantime I've take a look at the Jason code and I've found that the
trouble has to be probably in the internal action "send". In practice, as
you can see from the output above, the "send" action expects as its third
argument a literal and not a string... Well, removing the literal parsing
step from the send function and sending the string as it is (except for the
beginning and the ending quotes '"'), everything _seems_ to work well...
but I haven't got enough time to test it deeply yet!! :)

Please find in attachment the tarball of a working test agents to be used
with my own version of send.java (attached as mysend.java). For your
convenience I report here below also the unified patch for mysend.java, to
be applied to "send.java" with the command "patch -p0 < send.patch".

Ciao,
Alessandro

--- send.java	2004-09-22 14:47:23.357339016 +0200
+++ mysend.java	2004-09-22 14:23:35.364426936 +0200
@@ -30,23 +30,22 @@
 import jason.TransitionSystem;
 import jason.Unifier;
 
-public class send {
+public class mysend {
     
     public static boolean execute(TransitionSystem ts, Unifier un, String[] args) throws Exception {
         String to  = null;
         String ilf = null;
-        Pred pcnt  = null;
-        
+	String pcnt = null;
+
         try {
             to  = args[0];
             ilf = args[1];
-            pcnt  = Literal.parseL(args[2]);
+	    pcnt = args[2].substring(1, args[2].length() - 1);
         } catch (ArrayIndexOutOfBoundsException e) {
-            throw new JasonException("The internal action 'send' has not received three arguments");
+            throw new JasonException("The internal action 'mysend' has not received three arguments");
         }
-        un.apply(pcnt);
         
-        Message m = new Message(ilf, null, to, pcnt.toString());
+        Message m = new Message(ilf, null, to, pcnt);
         
         try {
             ts.getAgArch().sendMsg(m);


-- 
Alessandro Di Marco            http://www.disi.unige.it/person/DimarcoA/
DISI - Universita' di Genova   via Dodecaneso 35   16146 Genova,   Italy
phone +39 010 353 6719         fax +39 010 353 6699    dm...@di...
------------------------------------------------------------------------

Hi Alessandro,

> tellHow how?

Good question! :-)

Thanks for your message, we really need to make this clearer
in the manual.

When you use ".send" with "tellHow" as illocutionary force, the 3rd argument is
expected to be a term in the form of a string that can be *parsed* into a plan
(exactly as the plans in text source code are parsed into the initial plan
library). So, at the moment if in plan p1 (with triggering event te1(t) and
context c1(t)) you know you need to send, to ag2, plan p2 (with triggering
event te2(t), context c2(t) and body a2(t)) you can give your agent a plan
like this:

p1 ->
te1(t) :
  c1(y) <-
    .send(ag2,tellHow,"p2 -> te2(t) : c2(t) <- a2(t).").

This should already run in Jason, hopefully with no problems.
What you cannot yet do is to retrieve a plan (using, e.g., a matching
triggering event as criteria) from the agent's own plan library. But this
is easy to do, and should be done with an internal action such as:

.retrievePlan(te(X),Y)

then in subsequent actions in the body (or context) of a plan,
Y will be instantiated with the string representation of all
plans whose triggering events match te(X).

Because of the nature of such action (i.e., accessing agent's "internals") it
should be a "standard" internal action (i.e., available with Jason's
distribution), and we will certainly provide it when 0.5 is released. But
becuase we are all a bit busy at the moment, this may take a while. Perhaps
you should try to create your own if you need it soon, and if you have trouble
doing so, just let me know and I'll try to help.

Ciao,

Rafael


Alessandro Di Marco writes:
 > Hello, 
 > 
 > I'm wondering if you could help me to find a correct way to send
 > a plan from an agent to another. Reading the Jason manual I've discovered
 > that this can be accomplished using the internal action ".send" with the
 > force "tellHow", but every attempt I've made so far had no results.
 > 
 > Reading the Jason concrete syntax I see that .send accepts only annotated
 > atomic formuale (at), while the transition system accepting the
 > .send message (see TransitionSystem.java in/src/jason) requires a plan (p)!
 > 
 > As temporary solution I've managed to translate the annotated formulae in
 > the .send message to a plan directly in the transition system, but I'm
 > still searching for a more efficient and flexible way to do so.
 > 
 > Thanks in advance.
 > 
 > Regards,
 > Alessandro

Hello, 

I'm wondering if you could help me to find a correct way to send
a plan from an agent to another. Reading the Jason manual I've discovered
that this can be accomplished using the internal action ".send" with the
force "tellHow", but every attempt I've made so far had no results.

Reading the Jason concrete syntax I see that .send accepts only annotated
atomic formuale (at), while the transition system accepting the
.send message (see TransitionSystem.java in/src/jason) requires a plan (p)!

As temporary solution I've managed to translate the annotated formulae in
the .send message to a plan directly in the transition system, but I'm
still searching for a more efficient and flexible way to do so.

Thanks in advance.

Regards,
Alessandro

Dear George,

Thanks very much for your feedback on using Jason. This is much
appreciated.

Indeed, the environment can easily become a bottleneck, the way it is
currenlty implemented. Normally an action is implemented as a direct
change in the set of true facts about the enviroment (which can
potentially become percepts). In that case, the current setup for the
enviroment is not too bad. But if you have lots of agents whose
actions are more or less independent and require "processing" on the
part of the environment, then this current setup is not so good. The
reason Jomi and I chose to do it like this is to avoid users having to
know how to use "synchronize" in their code before accessing the
percepts. We try to make the use of Jason as high level as
possible. So currently, each agent runs in a separate thread but the
system synchronises automatically the execution of the executAction
method.

We still haven't decided exactly what we'll do, but version 0.5 will
have some alternative to avoid this problem (possibly to different
types of Environment classes, configurable on the .mas2j file, but we
are not sure yet).

Regards,

Rafael

/----------------------------------------------------------------\
| Dr. Rafael H. Bordini               Phone: +44 (0)191 334 1727 |
| Department of Computer Science      Fax:   +44 (0)191 334 1701 |
| University of Durham                    R.B...@du... |
| Durham DH1 3LE, U.K.            http://www.dur.ac.uk/r.bordini |
\----------------------------------------------------------------/

<html><div style='background-color:'><DIV class=RTE>Hi,</DIV>
<DIV class=RTE>&nbsp;</DIV>
<DIV class=RTE>For my final year computer science project at University I am learning to program multi-agent systems in Jason/AgentSpeak. I haven't done much in the area of agents before and am enjoying learning the language... version 0.4 was a huge help, as I was struggling with the global nature of percepts using 0.3, the ability to send to individual agents came in very handy.</DIV>
<DIV class=RTE>&nbsp;</DIV>
<DIV class=RTE>To learn Jason, I have started by implementing a simple environment with&nbsp;basic resource collecting agents. I have run into a bit of trouble in including a large number of agents. If I leave them all on the same thread, agents get 'greedy', and some will move while others wait for access to the perform the action method. However, as I do not yet fully understand the inner mechansims of Jason, the only way I have found to place each agent on its own thread is to create an anonymous thread inside the executeAction() method. This means that the agents can all act imultaneously, but have to start a new thread each time they perform an action. Thousands of threads quickly build up and the system eventually runs out of memory. My attempts to remove threads after executeAction() has run have proved unsuccessful, trying Thread.destroy and Thread.join has still meant that new threads are created when the agent next performs an action.</DIV>
<DIV class=RTE>&nbsp;</DIV>
<DIV class=RTE>I think the ideal situation would be to run each agent on a separate thread, from the moment it is created. This way they will all run simultaneously on a continuous small set of threads. Could you suggest how I might go about this, or if you think there is a better way to solve my problem, what that might be.</DIV>
<DIV class=RTE>&nbsp;</DIV>
<DIV class=RTE>I've only been using Jason for a couple of weeks, so I apologise if I've confused the matter or am missing something obvious.</DIV>
<DIV class=RTE>&nbsp;</DIV>
<DIV class=RTE>Thanks for your help,</DIV>
<DIV class=RTE>&nbsp;</DIV>
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