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From Jorge <>
Subject Re: [SCXML] Executor Questions
Date Thu, 19 Feb 2009 16:38:09 GMT

I am not an SCXML master, but as far as I understand the context and the 
evaluators are attached to the engine.

The context is in charge of keeping the data model from the SCXML 
executor. And the evaluator can have different forms depending on the 
expressions you are willing to evaluate in your SCXML xml file.

So, your ????? part, should listen to the protocol and fire events to 
the SCXML engine. And also the other way round, listen to the engine and 
fire events through the protocol. I can't see the problem on that as you 
can create the engine with for example a JexlContext and a JexlEvaluator 
and and run your state machine, isn't it?

In order to start your engine, I recommend you to take a look to the 
AbstractStateMachine code as a complete example on it.

On the other hand, I consider very interesting that you use a graphical 
editor to edit your scxml, I think there is not anything like that in 
the web, isn't?



Linda Erlenhov wrote:
> Hello again.
> Doesn´t anybody have a solution to my problem?
> I don´t know if maybe theres something I need to clarify.
> The engine sends "messages" that are java objects that I in the (?????) part
> translates to somethin on the form that the ApacheEngine wants.
> What I don´t understand is what I should do with the "context" and
> "evauator" in my model, can I work around it somehow?
> best regards
> //Linda
> On Tue, Feb 17, 2009 at 1:52 PM, Linda Erlenhov <>wrote:
>> Hello
>> I have just begun using the Apache SCXML  and I have encountered a problem.
>> This is what already is:
>> I have an editor for HMI. You build the interfaces using modules and then
>> connects to actions and events in a databas and this is then run by another
>> engine that sends events/actions (for some strange reasond they are named
>> the "wrong" way in this program, i didn´t build it so...) to a CD player or
>> whatever through a protocol via an interface.
>> My job:
>>  is to build a simulator for the "cd-player" part. The" tricky" is that it
>> should be generic, so that the client can build whatever kind of machine he
>> or she wants to.
>> I have created a graphical interface with GMF in eclipse where you can
>> build statemachines with the help of "modules" representing states,
>> transitions etc. This generates a XML representation of  the statemachine
>> once it´s finished and then that is translated into SCXML. So far so good.
>> so what we have here now is HMIeditor <-> DB <-> Engine <-> protocol
>> (??????) <-> Apache engine<->SCXML<->XML <-> my editor for
>> All the functions (actions, events etc.) of the "cd-player" is described in
>> a XML file wich both the HMI editor and my editor uses so I can put them on
>> any form I want to and I have knowledge in what the HMIeditorengine "does"
>> to the data.
>> This is what I think is the problem (above shown as (??????)):
>> Between the apache engine and the protocol ther should be an interface
>> (duh). My interface there should start up both engines and then (i think)
>> listen to two buffers (i´m thinking two threads), my interface takes care of
>> the translation from the protocol data look to the ApacheEngines data look.
>> I just don´t undstand now how I should start up the Apache engine. I don't
>> understand what i need the context and evaluator and so on for, the things
>> that the apache engine recieves should be on the form it wants?
>> Or have I just misunderstood?
>> I hope someone understands something of what my problem is.
>> best regards
>> //Linda


Jorge Vila Forcén
Networked Vehicles Division                   Mail:
TELEFONICA I+D                                Tel: +34 91 337 2614
Emilio Vargas, 6 28043 Madrid(SPAIN)          

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