RE: SDL-News: signal-delays

Subject: RE: SDL-News: signal-delays
From: Rick Reed (
Date: Mon Oct 29 2001 - 14:04:12 GMT

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Dear Patrick,
I understand from what you say, that you are interested in
validation/verification (or even performance evaluation or test case
generation) of SDL models, and this is why you may need to have =
channel delays.=20
This feature is not so much interesting for people only interested in =
generation from SDL models (even if it allows a more correct validation =
the model). This is why commercial tools do not generally provide =
means for that.
Nevertheless, it is a well-known (and poorly-resolved) problem for SDL
People using the commercial versions of ObjectGeode (the other SDL tool =
Telelogic) can use some channel delay specifications included in =
like for example=20
       CHANNEL C1 COMMENT "##delay 1,5,uni";=20
meaning C1 delays messages uniformally from 1 to 5 time units, and this =
taken into account by the interactive or random simulator.
It is not complete (not allowed for exhaustive verification), and no
possibility provided for unreliable channels.
An ongoing european project (IST INTERVAL) (see
<> ) is currently working on the topic of timed
extensions for SDL, MSC and TTCN.
This project has some interesting results namely for SDL :

* proposed SDL extensions to ITU-T/SG17 : these extensions are
currently handled by the ad hoc question Q23 on time and performance for SDL
in order to go in the standard
* a prototype (build on Telelogic/ObjectGeode) implementing most of
these extensions : channel delays, lossy channels, task delays, clocks,
urgencies ... This proto is not distributed at the moment by Telelogic, but
is used in the Interval project for some experiments by Ericsson (S), France
Telecom (F) and Teletel (Gr).

Hope it helps. Daniel Vincent=20
& france telecom

Technopole Anticipa Tel: +33 2 96 05 39 54
2, Avenue Pierre Marzin Fax: +33 2 96 05 39 45

--End text from Rick Reed <> to sdlnews ---
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