Re: SDL-News: What does this mean?

Subject: Re: SDL-News: What does this mean?
From: Laurent DOLDI (
Date: Fri Mar 08 2002 - 09:05:36 GMT

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-----From Laurent DOLDI <> to sdlnews -----

Dear Mr. Yongqian,

At 11:17 08/03/02 +0800, you wrote:
>Hello, all,
>I am reading a paper about the timing limit of SDL. There is a section as
below. I am not sure
>the meaning of it. Would you like to give me a hand? (The paragraph marked
with "~~~" puzzle me )
> " A typical assumption on the progress of time in SDL, as has been
adopted by most tool vendors [13,14] is to assume that time only progresses
when the system is in a stable inactive state, i.e. where no signals can be
sent or consumed. With regard to real-time systems development, this is of
limited use since with this approach when no timers are currently set then
time, in effect, does not

In ObjectGEODE, since 1996, the Simulator option "loose time
progression" allows to:

- either have the behaviour you mention,
- or, if set to True, to allow the time to progress as soon as
  a timer is set, even if the queues are not empty etc.

>Further, since timer expiry results in an input signal being placed in the
(possibly non-
>empty) input queue of the associated agent, these signals can be in the
queue any arbitrary time before they are consumed. If the expired timer was
to stop delivering plutonium, then such a delayed
>treatment is unlikely to be satisfactory. "

It seems that a deterministic architecture (as in the Airbus
A320 flight controls, if they fail 180 people die, it is less
dangerous than plutonium) would suit better the requirement
to stop the plutonium.

With kind regards,

Laurent DOLDI *** new book: SDL Illustrated *** (see my web site)
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