Re: Definition of ``codel'' + ``execution engine'' ...

From what Sara, Anthony and Raja said I understood that:

CODEL - is a piece of code and variables local to it, that is designated for
execution by the execution engine. Codel's execution should never be
interrupted by the execution engine.  The return code (state) of the codel
enables the execution engine to make decisions as to the designation of the
next codel (perhaps more than one if parallel execution is possible) for
execution.

EXECUTION ENGINE - a part of the component that is an automaton that
designates codels for execution. It decides which codel to execute next by
considering the return values of previously executed codels and the state of
the data base of the component.

I still don't like the name "data base" for that global repository of the
component.

I think that the structure of the LAAS component should also be defined here
(I think that a drowing would be very helpful).

I hope that true definitilons will reach us from LAAS, but perhaps it will
be easirer for them to clarify the misunderstandings, if we deliver our own
definitions.

Cezary

----- Original Message -----
From: "Herman Bruyninckx" <[email protected]>
To: "Open RObot COntrol Software" <[email protected]>
Sent: Wednesday, February 06, 2002 9:58 PM
Subject: [Orocos] Definition of ``codel'' + ``execution engine'' ...


> I'm reworking the website, to bring it somewhat in sync with the
> evolution of the last months. One of the important concepts that need
> clarification for newcomers (and not-so-newcomers :-) is the
> ``codel''. I'll try a definition, but please correct and complement
> it.
>
> Another topic is the ``execution engine''. (Or should I call it
otherwise?)
>
> Do I have to put other definitions on-line? If so, please send me
> inputs. (Via the mailing list!)
>
>
> Herman
> ==============================================
> Codel: any part of a component that must be executed atomically,
> within the context of this component. In this sense, it is the basic
> building block of an Execution engine.
> It is important to stress that the atomicity must hold only within the
> component only; the operating system can preempt the codel by
> scheduling of other components. (Unless the codel takes explicit
> actions to make pre-emption impossible.)
>
> Execution engine (also known as: task execution control, task
> sequencing):  the infrastructure software that takes care of the
> proper execution of a given task, within the context of some
> state-based task sequence (Finite State Automaton; Petri Net;
> Hierarchical State Machine; StateCharts; ...). Each state has a codel
> that contains the basic functional part of the task in that state, and
> some auxiliary functions, that implement what must be done at state
> entry and state exit.
> The execution engine helps, for example, to implement controllers that
> have to switch their control algorithms on-line (e.g., in the control
> of a walking device).
>
>
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