Re: SDL-News: SDL transitions

Subject: Re: SDL-News: SDL transitions
From: Rick Reed TSE (rickreed#tseng.co.uk)
Date: Wed Sep 15 1999 - 13:02:23 GMT

Joerg Hintelmann <jh#informatik.uni-essen.de> wrote
> Does the semantic of SDL postulate the atomicity of SDL-transitions?

This is a FAQ. The short answer is "yes".

A longer answer is another question: What do YOU mean by "atomicity"?

Both MSC and SDL assume that the entities with behaviour have concurrent
existences (even though formal models of the languages may assume
interleaved behaviour - it is postulated that there is no observable
difference between interleaved models and true concurrency).

In SDL once a transition has been initiated then it continues until an
explicit or implicit state has been reached or the process instance
terminates. However, what may appear to be an single transition, may in fact
have explicit states hidden within procedure calls, or implicit states
hidden by the use of language features such as IMPORT.

A more complete answer can be given for SDL, if the criteria for "atomicity"
are more precisely defined.

I think the SDL news archive (which I think you can find on the
www.sdl-forum.org pages) contains some discussion on this topic.

I'll let an MSC guru give a more complete answer for MSCs. 

--
Rick Reed - rickreed#tseng.co.uk
Tel:+44 1455 55 96 55 Fax:+44 1455 55 96 58 Mob.:+44 7970 50 96 50
Re: SDL-News: SDL transitions Joerg Hintelmann  <jh#informatik.uni-essen.de>  wrote
> Does the semantic of SDL postulate the atomicity of SDL-transitions?

This is a FAQ. The short answer is "yes".

A longer answer is another question: What do YOU mean by "atomicity"?

Both MSC and SDL assume that the entities with behaviour have concurrent existences (even though formal models of the languages may assume interleaved behaviour - it is postulated that there is no observable difference between interleaved models and true concurrency).

In SDL once a transition has been initiated then it continues until an explicit or implicit state has been reached or the process instance terminates. However, what may appear to be an single transition, may in fact have explicit states hidden within procedure calls, or implicit states hidden by the use of language features such as IMPORT.

A more complete answer can be given for SDL, if the criteria for "atomicity" are more precisely defined.

I think the SDL news archive (which I think you can find on the www.sdl-forum.org pages) contains some discussion on this topic.

I'll let an MSC guru give a more complete answer for MSCs.
--
Rick Reed - rickreed#tseng.co.uk
Tel:+44 1455 55 96 55 Fax:+44 1455 55 96 58 Mob.:+44 7970 50 96 50

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