Re: MSC-News: The loop operator

Subject: Re: MSC-News: The loop operator
From: Oystein Haugen (
Date: Fri Jan 30 1998 - 13:08:49 GMT

The originator of this message is responsible for its content.
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Lennard Lambert wrote:

> The originator of this message is responsible for its content.
> -----From Lennard Lambert <>
> to mscnews -----
> Dear Dagbjoern Nogva,
> Does the loop operator denote a parallel loop or a sequential
> loop? By parallel loop I mean that all iterations are executed
> in parallel.
> As far as I can see, Z.120 doesn't say anything specific, however
> I guess the answer is sequential loop, i.e. each iteration is
> executed in sequence.
> I had a short look up and I have also not found any precise
> definition. But in section 6.20 an exapmle is given that confirms
> your opinion.
> If so, is it possible to specify a parallel
> loop by combining the par operator and the loop operator in some
> way? Or do I just have to make a comment?
> In our annotational extension of MSC-96 to integrate performance
> issues, called Performance MSC, we had the same problem. We want to
> express a parallel composition of parallel loops. Since annotational
> extension means comments with semantics to our tools, we had no
> problem using the comment variant.
> I do not see how a combination of par and loop operators can help to
> express a parallel loop within the current semantics of MSC-96 since
> an instance in the loop can only start its next iteration after it has
> completed the current one.
> Best regards
> Lennard Lambert

Dear Dagbjorn, Lennard and the other MSC fans

Even though it may be difficult (impossible) to find an explicit
mentioning of which operator is involved in a loop, it is right that the
assumed interpretation is that the loop is the repeated application of
the seq operator (which is defined as weak sequencing).

Since the loop if inline expressions corresponds loosely with cycles of
the HMSC, this is a reasonable interpretation. I agree that this should
probably have been more explicitly stated. You should also know that we
have discussed in the standardization group other operators as the base
for a repetition construct (such as par). We would be grateful to
receive examples to support such an improvement such that this can be
considered when we discuss future extensions of the list of operators.

Oystein Haugen
Rapporteur MSC

Oystein Haugen, Ericsson as. , P.O. box 34, N-1361 Billingstad, Norway
Tel: +47 66 84 23 46 Fax: +47 66 84 19 15 E-mail:

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