Subject: Fwd: Re: SDL-News: Fwd: [SDLTF-Members] SDL IS IN DANGER
From: William H. Skelton (W.Skelton#SOLINET.com)
Date: Fri Dec 19 2003 - 07:52:10 GMT
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-----From "William H. Skelton" <W.Skelton#SOLINET.com> to sdlnews -----
Dear Susanne,
Thank you for this useful background; my comments below...
For anyone else interested, the save discussion is still going on, you can
register at www.SDL-Task-Force.org.
William
>Date: Thu, 18 Dec 2003 20:11:42 +0100
>From: Susanne Graf <Susanne.Graf#imag.fr>
>
>Dear William,
>
>Laurent is right, one should be careful before throughing the save
>construct away. As I already explained in an earlier mail. SAVE is very
>different from the use of priorities. You cannot replace the SAVE
>construct by priorities otherwise than in a very odd manner.
We are being careful and that is why we are discussing it so much. :-)
>SAVE construct can be used for bad reasons:
Thanks for these examples.
>1. first a bad one: if there are two signals a process waiting for, which
>may arrive in any order. One sees then often specifications which, in
>order to avoid the explicit interleavings use SAVE in order to force the
>consumption in a particular order.
>Duplication of programm text is not desirable, but here paralleising the
>independent activities would be the nicer solution.
How could this parallelizing be done?
>2. now, if there exists constraints on the order in which a process can
>execute certain activities, for example A2 should never be executed before
>an A1 has been done, and the processes triggering these activities are not
>necessarily symchronized or don't even know about these order constraints,
>then there exist 2 solutions:
> a) through requests which cannot be served away
> b) but honsestly, this is not always a solution. Another solution is to
> store the information that the request is there and do it when a state
> allowing this activity is reached. Obviously you can now introduce a new
> variable saving the request and it's parameters (may be even several of
> them), but the simplest solution is to maintain the signal in the signal queue.
OK, we have been discussing this under the heading of 'packet buffering'
with these notes:
-- SDL and save doesn't allow an atomic flushing of the saved signals.
-- It means one state may depend on side-effects from another state, the
hot-potato problem.
-- An explicit queue is closer to traditional software methods and closer
to the application, which is best able to manage it.
-- It is not clear maintaining the signal in the input queue is the
'simplest' solution.
>regards,
>Susanne
>
>William H. Skelton wrote:
>>Become an SDL Forum Society member
>><http://www.sdl-forum.org/Society/members.htm>
>>The originator of this message is responsible for its content.
>>-----From "William H. Skelton" <W.Skelton#SOLINET.com> to sdlnews -----
>>Dear Doldi,
>>We are having a discussion based on technical justification; there is no
>>need for this reaction...
>>I am genuinely interested in your comments, and I request you to respect
>>what we are trying to achieve, namely a simple, useful version of SDL; to
>>increase the awareness and acceptance of the language, from having 50
>>participants at the bi-annual SDL conference, when the regional Java
>>forum had 750 at the same time and location!
>>You talk about trying to defend SDL, but our activities are a serious
>>attempt to take it forwards, from a position that has a monopoly tool
>>supplier, who apparently has little interest in the SDL Forum and a
>>specification that no-one seems to be interested in fully supporting
>>(SDL-2000).
>>No-one doubts your credentials, but I'm afraid we expect you to address
>>the issues at stake and not expect us to accept something as
>>'untouchable', just because it comes from your email address. :-)
>>Why not roll up your sleeves, join in the discussion and let us all
>>benefit from your experience?
>>William
>>
>>>X-Sender: doldi.laurent#pop.wanadoo.fr
>>>X-Mailer: QUALCOMM Windows Eudora Version 6.0.0.22
>>>Date: Thu, 18 Dec 2003 15:35:39 +0100
>>>To: members#sdl-task-force.org
>>>From: doldi.laurent#tmso-systems.com
>>>Subject: [SDLTF-Members] SDL IS IN DANGER
>>>Cc: sdlnews#sdl-forum.org, damyot#site.uottawa.ca
>>>Sender: members-owner#sdl-task-force.org
>>>Reply-To: members#sdl-task-force.org
>>>
>>>THANK YOU FOR THE 'imaginary case'. I HAVE BEEN WORKING WITH SDL AND
>>>OTHER LANGUAGES SINCE 1982, ON REAL APPLICATIONS THAT ARE NOW
>>>FLYING OR RUNNING, SUCH AS THE AIRBUS A310, A320, UMTS OR GPRS
>>>SYSTEMS, SATELLITE COM. SYSTEMS ETC.
>>>
>>>PLEASE REMOVE ME FROM THE SAM04 PROGRAM COMMITEE.
>>>
>>>To sdl news: WHY ONLY 3 OR 4 PERSONS REACT TO THIS ATTEMPT TO
>>>DESTROY SDL?! COME ON SDL FORUM, DEFEND SDL!
>>>
>>>Laurent Doldi.
>>>
>>>At 13:21 18/12/2003, you wrote:
>>>
>>>>Dear Doldi,
>>>>
>>>>Thank you for this comment.
>>>>
>>>>My first impression is that this is not a real requirement, but an
>>>>imaginary case taken from what is possible with save.
>>>>
>>>>If there is a real requirement to implement this, and I have my doubts
>>>>even then that this is something we should encourgae, it probably falls
>>>>into the ordering problem that Qing has been looking at, and for which
>>>>there is a proposal of a clean mechanism that limits the scope of this
>>>>ordering.
>>>>
>>>>What do you think?
>>>>
>>>>William
>>>>
>>>>>X-Sender: doldi.laurent#pop.wanadoo.fr
>>>>>X-Mailer: QUALCOMM Windows Eudora Version 6.0.0.22
>>>>>Date: Thu, 18 Dec 2003 12:41:03 +0100
>>>>>To: members#sdl-task-force.org
>>>>>From: doldi.laurent#tmso-systems.com
>>>>>Subject: [SDLTF-Members] Doldi thinking we want to buffer signals
>>>>>Sender: members-owner#sdl-task-force.org
>>>>>Reply-To: members#sdl-task-force.org
>>>>>
>>>>>Dear Task Force,
>>>>>
>>>>>If you do not buffer the signal and remove SAVE from the subset, how
>>>>>do you
>>>>>write the following:
>>>>>
>>>>>A process (instance) P has signals S1 and S2 in its queue (S1 being
>>>>>first).
>>>>>In state ST1, P must input S2, and signal S1 must be processed later (in
>>>>>a state ST2):
>>>>>
>>>>>DCL
>>>>> x x_t,
>>>>> y y_t;
>>>>>
>>>>>STATE ST1;
>>>>> INPUT S2(y); etc. ; NEXSTATE ST2;
>>>>> SAVE S1;
>>>>>
>>>>>STATE ST2;
>>>>> INPUT S1(x); etc.
>>>>>
>>>>>What is the equivalent without using SAVE ?
>>>>>
>>>>>Regards,
>>>>>Laurent.
>>>>>
>>>>>At 23:30 17/12/2003, you wrote:
>>>>>
>>>>>>In some case there was simply a misunderstanding, form example Doldi
>>>>>>thinking we want to buffer signals, when actually we were talking
>>>>>>about the parameters carried by a signal (a big difference between a
>>>>>>system feature and an application feature).
>>>>
>>>>
>>>>------------------------------------------------------------------------
>>>>William H. Skelton, Engineering Dept.
>>>>SOLINET GmbH Solutions for Innovative Networks
>>>>Mittlerer Pfad 26, 70499 Stuttgart, Germany
>>>>Tel +49 711 1398 1377, Fax +49 711 866 1240
>>>>Mobile +49 171 247 6688
>>>>W.Skelton#SOLINET.com, www.SOLINET.com
>>>
>>>
>>>Laurent DOLDI
>>>TransMeth Sud-Ouest
>>>27, av. Segoffin 31400 TOULOUSE FRANCE
>>>Tel.: +33 5 61 25 59 54 Fax: +33 5 61 25 82 17
>>>Mobile: +33 6 80 26 62 31
>>
>>------------------------------------------------------------------------
>>William H. Skelton, Engineering Dept.
>>SOLINET GmbH Solutions for Innovative Networks
>>Mittlerer Pfad 26, 70499 Stuttgart, Germany
>>Tel +49 711 1398 1377, Fax +49 711 866 1240
>>Mobile +49 171 247 6688
>>W.Skelton#SOLINET.com, www.SOLINET.com
>>
>>--End text from "William H. Skelton" <W.Skelton#SOLINET.com> to sdlnews ---
>>For extra SDL Forum Society benefits join at
>><http://www.sdl-forum.org/Society/members.htm>
>>For help, email "majordomo#sdl-forum.org" with the body of your email as:
>> help
>>or (iff this does not answer your question) email:
>>owner-sdlnews#sdl-forum.org
>
>
>--
>------------------------------------------------------------------------
>Susanne Graf | tel : (+33) (0)4 56 52 03 52
>VERIMAG | fax : (+33) (0)4 56 52 03 44
>2, avenue de Vignate | http://www-verimag.imag.fr/~graf/
>F - 38610 Gieres | e-mail: Susanne.Graf#imag.fr
>------------------------------------------------------------------------
>
>--End text from Susanne Graf <Susanne.Graf#imag.fr> to sdlnews ---
>For extra SDL Forum Society benefits join at
><http://www.sdl-forum.org/Society/members.htm>
>For help, email "majordomo#sdl-forum.org" with the body of your email as:
> help
>or (iff this does not answer your question) email: owner-sdlnews#sdl-forum.org
------------------------------------------------------------------------
William H. Skelton, Engineering Dept.
SOLINET GmbH Solutions for Innovative Networks
Mittlerer Pfad 26, 70499 Stuttgart, Germany
Tel +49 711 1398 1377, Fax +49 711 866 1240
Mobile +49 171 247 6688
W.Skelton#SOLINET.com, www.SOLINET.com
--End text from "William H. Skelton" <W.Skelton#SOLINET.com> to sdlnews ---
For extra SDL Forum Society benefits join at <http://www.sdl-forum.org/Society/members.htm>
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