SDL-News: Re: [SDLTF-Members] Summary of SAVE Issues Discussed

Subject: SDL-News: Re: [SDLTF-Members] Summary of SAVE Issues Discussed
From: Rick Reed TSE (
Date: Thu Dec 04 2003 - 21:45:27 GMT

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William H. Skelton at wrote on 04/12/2003 18:31:

> 1.2) There has been confusion about how the save construct works and why it
> is useful (execution model is not transparent, inter-state dependencies are
> created). Apart from state reduction, there have been no applications
> presented where it is needed (William).

I would be surprised if anyone that has used SDL tools such as Cinderella,
GEODE or SDT to any extent is confused about the way that SAVE works.

I do not agree with the analysis that "Apart from state reduction, there
have been no applications presented where it is needed". It seems to me that
several examples were given, and Philipp gave an example that is difficult
to put into SDL without SAVE, because there is a state explosion otherwise.
> 1.4) Spontaneous transitions are not in the subset; are they needed (Philipp)?

If the subset is to enable test stubs to be written, then I would think they
would be needed.
> 2.1) There are no operators in pre SDL-2000 that allow SEQUENCE OF to be
> manipulated(!!!)

This is an incorrect statement.

The operators were defined when it was allowed to use ASN.1 data with SDL -
standardised by Z.105 March 1995.

These operators are supported by SDL tools.

> and SDL-2000 strings and operators are not in the SDL
> subset.

Strings are not an SDL-2000 feature. They existed in SDL-92, SDL-88 and

I was under the impression that the supported data types and operations were
under discussion.

> An analysis of how to use SDL-2000 operators on SEQUENCE OF, which
> is a valid SDL/ASN.1 type in the subset, is pending (Alkis).

Is there a good reason to deviate from ITU-T SDL?

Rick Reed -
Tel:+44 15394 88462 Mob.:+44 7970 50 96 50

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