Example 11 - Working in Remote Workspaces

Agents can join workspaces that are hosted on remote nodes, by means of a 
<code>joinRemoteWorkspace</code> action (provided by the <code>NodeArtifact</code>.
As soon as the join succeed, the interaction within remote workspaces is the same as local workspace.
In the following example, a Jason agent joins the default workspace of a CArtAgO node running on localhost.
The following Java program installs a  CArtAgO node on localhost, to make it reachable (also) by remote agents:

<blockquote>
<pre>
package examples;

import cartago.*;
import cartago.util.BasicLogger;

public class Ex00a_HelloRemoteWorld {
	
  public static void main(String[] args) throws Exception {			
    CartagoService.startNode();
    CartagoService.installInfrastructureLayer("default");
    CartagoService.startInfrastructureService("default");
    CartagoService.registerLogger("default",new BasicLogger());  
    System.out.println("CArtAgO Node Ready.");
  }
}
</pre>
</blockquote>
<strong>Highlights:</strong>
%
<ul>
	<li> <strong>Starting a CArtAgO Node:</strong> to execute CArtAgO artifact-based environment, first of all a CArtAgO node must be started. 
	This is done by the <code>startNode</code> service of <code>CartagoService</code>.
	The node functions as virtual machine for running workspaces and artifacts, it does 
	not include any infrastructural (network) support.</li>

<li> <strong>Installing infrastructure layers:</strong> in order to allow agents working in the 
local node to interact also with remote nodes - or to allow linking with remote artifacts - 
a proper infrastructural layer must be installed by means of <code>installInfrastructureLayer</code>, 
specifying the protocol(s) to be used (<code>default</code> means the default protocol of 
the platform, which is RMI in the case of Java SE desktop environments).</li>

<li> <strong>Intalling infrastructure services:</strong> in order to make the node reachable 
from remote agents, then infrastructure services must be started by means of 
<code>startInfrastructureService</code>, again specifying the protocol.</li>
</ul>

Then, it follows the Jason program which creates a standalone CArtAgO node with a single agent:
<blockquote>
<pre>
MAS example11_remote {

  environment: 
  c4jason.CartagoEnvironment

  agents:  
  voyager agentArchClass c4jason.CAgentArch;

  classpath: "../../../lib/cartago.jar";"../../../lib/c4jason.jar";    
}
</pre>
</blockquote>

The <code>voyager</code> agent boots in the standalone node, then it joins a remote 
workspace, where he creates and uses an artifact. 
<blockquote>
<pre>
!test_remote.

+!test_remote 
  <- ?current_wsp(Id,_,_);
     +default_wsp(Id);
     println("testing remote..");
     joinRemoteWorkspace("default","localhost",WspID2);
     ?current_wsp(_,WName,_);
     println("hello there ",WName);
     !use_remote;
     quitWorkspace.
      
+!use_remote 
  <- makeArtifact("c0","examples.Counter",[],Id);
     focus(Id);
     inc;
     inc.

+count(V) 
  <- ?default_wsp(Id);
     println("count changed: ",V)[wsp_id(Id)].
  
-!use_remote [makeArtifactFailure("artifact_already_present",_)]
  <- ?default_wsp(WId);
     println("artifact already created ")[wsp_id(WId)];
     lookupArtifact("c0",Id);
     focus(Id);
     inc.   
</pre>
</blockquote>
<strong>Highlights:</strong>

<ul>
<li> <strong>Infrastructure options:</strong> By default, Jason programs using CArtAgO environment 
create a standalone CArtAgO node, i.e. not accessible through the network, 
and install the default infrastructure layer (RMI) for joining remote workspaces. 
Besides the default CArtAgO installation, Jason programs have the possibility to work 
with CArtAgO environment technology in four different ways specifying a set 
of parameters in the <code>c4jason.CartagoEnvironment</code> definition inside the 
Jason <code>mas2j</code> file:


<ul><li> <code>c4jason.CartagoEnvironment("standalone", protocol(ProtName), ...)</code>: analogous 
to the default installation except for the declaration of one (or more) 
infrastructure layers that specify the protocols used for working with remote 
workspaces (ex: <code>c4jason.CartagoEnvironment("standalone",protocol(lipermi))</code>.</li>


<li> <code>c4jason.CartagoEnvironment("infrastructure",protocol(ProtName), ..., service(ServName))</code>: 
installs a CArtAgO node accessible through the network. The default service protocol 
supported by the node is RMI, other service protocols can be installed specifying one 
or more <code>service</code> attributes. RMI is installed as the default protocol 
for joining remote workspaces but other protocols can be installed as well 
using the <code>protocol</code> attribute 
(ex: <code>c4jason.CartagoEnvironment("infrastructure", service("lipermi"), protocol("lipermi"))</code>).</li>


<li> <code>{c4jason.CartagoEnvironment("remote", WspName, WspAddress, protocol(ProtName, Address), ...)</code>: does not install any node - agents directly join the specified remote workspace. 
As usual RMI is installed  by default and further protocols can be specified using the <code>protocol</code> attribute 
(ex: <code>c4jason.CartagoEnvironment("remote", "myWsp", "localhost", protocol("lipermi"))</code>).</li>

<li> <code>c4jason.CartagoEnvironment("local",WspName)</code> does not install any node -- agents directly join the specified local workspace (or the default workspace if no workspace name is specified) (ex: c4jason.CartagoEnvironment("local", "WspName")).
</li>
</ul>
</li>
</ul>