ALFred Documentation

Implementation of an application using ALFred environment

The Esterel module SimpleEntity

module SimpleEntity:

%% declarations

% ADU type
type COMMAND;

% ADUs received from the network
input RcvRequest:COMMAND,
      RcvResponse:COMMAND;

% ADUs sent to the network
output SndRequest:COMMAND,
       SndResponse:COMMAND;

% input signal
input Request;
% output signal
output Print:string;

% functions
function Build_Request():COMMAND,
	 Build_Response():COMMAND;

%% body

    every RcvRequest do
     emit SndResponse(Build_Response());
    end every
  ||
    every Request do
     emit SndRequest(Build_Request());
     await RcvResponse;
     emit Print("Response Received");
    end every

end module

If you are under Emacs the menu "Alfred" should be added in the tool bar for the esterel+alfred mode. Press "Start ALFred" to enable ALFred menu for QoS setting.Now you just have to click on the ADU type COMMAND and fill in the pop up menu with the following values: partial-reliable/in-sequence/non-real-time/unicast. This will create a file called "SimpleEntity.qos":

 $ more SimpleEntity.qos
COMMAND    reliable         in-sequence     non-real-time    unicast   

• reliability: non-reliable | reliable | partial-reliable
• order of delilvery: out-of-sequence | in-sequence
• real-time: non-real-time | delay-sensitive | jitter-sensitive | deljit-sensitive
• mode: one-to-one | one-to-many | many-to-one | many-to-many

Parsing of SimpleEntity

For SimpleEntity the following files are generated by the parser:

 $ ls
 SimpleEntity.strl
 SimpleEntity.qos

 $ java inria.alfred.parser.Tool -f SimpleEntity


 $ ls
 AlfAppli.strl   QoSsetting.java     AlfAppliInterface.java   AlfAuto0Interface.java
 AlfAuto0.strl   AlfAppliRun.java    COMMAND.java

The parser also pops up a menu to enter more detailed QoS and/or modify the previously defined high-level QoS parameters. You can look for example at the menu display for the JukeBox application.

Let us have a look at the "AlfAppli.strl" file (we show only the newly generated code):

module AlfAppli : 
      :
      :
output RemoveCOMMAND : COMMAND ; 
input ApplClose;  

abort 
      :
|| 
 every Request do 
      :
  await RcvResponse do emit RemoveCOMMAND ( ? RcvResponse ) end await ; 
      :
 end every 
when ApplClose 

end module

The interface skeleton is in the file "AlfAppliInterface.strl":

/**
 * automatically generated by the alfred compiler (Tool.java).
 * skeleton of the data interface for the esterel application.
 * to be completed by the user ...
 */
// generated by inria.alfred.parser.Tool

import inria.alfred.lib.*;
import java.net.*;
import java.io.*;
import java.util.*;

// ----------------
// Interface class
// ----------------

public class AlfAppliInterface {

// BEGIN  of <<do not touch this part of code>>

  protected AppliHandler handler;
  protected AlfAppli auto;

  public void setAppliHandler (AppliHandler h) {
    handler=h;
  }
  public void setAppliAuto (AlfAppli a) {
    auto=a;
  }

//
// treatment of ADUs
//
  public void outRemoveCOMMAND (COMMAND val) { 
    handler.removeAdu("COMMAND", val);  // val:COMMAND
  }

  public void outSndRequest (COMMAND val) { 
    handler.sendAdu("COMMAND", (SndRequest)val);  // val:SndRequest
  }

  public void outSndResponse (COMMAND val) { 
    handler.sendAdu("COMMAND", (SndResponse)val);  // val:SndResponse
  }

// END of <<do not touch this part of code>>


//
// output signals
//
  public void outPrint (String val) { 
    System.out.println("Print");
   }

//
// sensors
//


//
// functions
//
   public COMMAND Build_Request () {
   return new COMMAND();
   }

   public COMMAND Build_Response () {
   return new COMMAND();
   }



//
// procedures
//
}

//
// ADU Type class
//

import inria.alfred.lib.ADU;
public class COMMAND implements ADU {
   public COMMAND () {}
}

class RcvRequest extends COMMAND {
}


class RcvResponse extends COMMAND {
}

class SndRequest extends COMMAND {
}

class SndResponse extends COMMAND {
}

/**
 * automatically generated by the alfred compiler (Tool.java).
 * skeleton of the data interface for the esterel application.
 * to be completed by the user ...
 */
// generated by inria.alfred.parser.Tool

import inria.alfred.lib.*;
import java.net.*;
import java.io.*;
import java.util.*;

// ----------------------------
// Application class definition
// ----------------------------
public class AlfAppliRun extends Thread implements QoSsetting {
  private AppliHandler handler=null;
  private AlfAppli auto;

  public AlfAppli getAuto () {
    return auto;
  }

  public void init () {
    // initialisation of QoS parameters by application
    AlfredService.setADU_TYPES_NB(ADU_TYPES_NB);
    AlfredService.setADUTYPE_NAME(ADUTYPE_NAME);
    AlfredService.setADU_NB(ADU_NB);
    AlfredService.setADU_NAME(ADU_NAME);
    AlfredService.setINPUT_ADU_NAME(INPUT_ADU_NAME);
    AlfredService.setQoS_table(QoS_table);
    AlfredService.setSEND_ONLY(SEND_ONLY);
    AlfredService.setRECV_ONLY(RECV_ONLY);
    AlfredService.setMechan_table(Mechan_table);
    AlfredService.setRbfcParams(RbfcParams);
    AlfredService.setINTERACTIVE(interactive);
    AlfredService.setTYPE_OF_DATA(type_of_data);
    // initialisation of application handler
     handler= new AppliHandler();
     AlfredService.setAppliHandler(handler);
  }


  public void run() {
   try {
     auto= (AlfAppli)handler.getAuto();
     auto.getInterface().setAppliHandler(handler);
     auto.getInterface().setAppliAuto(auto);

// BEGIN of user application code
//    ... auto.CSTE=...; auto.inputS(); (boolean)handler.runAuto(); ...      
// methods available: AlfredService.getAduPort(String adu_type) -> int
//                    AlfredService.getDestAddr(String adu_type) -> String



// END of user application code

   } catch(Exception e) {
     System.err.println("Exception: " + e.getClass().getName());
     System.err.println(e.getMessage());
     e.printStackTrace();
   }
  }

// if you want to define some command parameters uncoment
// the two following methods.
//    public static void showUsage () {}
//    public static String[] parseParameters(String args[]) {
//	String[] aux = new String [argv.length];
//	int j=0;	
//
//	for (int i = 0 ; i < argv.length ; i++) {
//
//	    if(argv[i].equals("-...")) {
//
//		......
//
//	    } else {
//		aux[j++]=argv[i];
//	    }
//	}
//
//	return aux;
//   }
}

As you can see, if you want to define command parameters you have to specify the two methods showUsage and parseParameters.
If you redefine a command parameter that is already in ALFred top level command, it's the user level parameter that will be treated. The price to pay to give advantage to application level command parameters is to return the array of parameters not treated by application in parseParameters.

Generation of SimpleEntity executable code

To compile the Esterel specification of control part of application/protocols you can proceed in two steps: first you translate the specification into ssc formalism, second you compile the result into Java with the ocjava tool. See Using ALFred for details.
The last step of compilation to java and then into executable code is also clearly described in the real case study of the JukeBox.

Note that Esterel is equipped with a comfortable programming environment including symbolic debugging, simulation tools (xes X-window simulation), compilation into both automata and circuits, graphical representation of automata, optimization and verification tools, etc. See the Esterel home page for more details.