Re: MSC-News: Problem with instance-oriented - shared in-line expression textual

Subject: Re: MSC-News: Problem with instance-oriented - shared in-line expression textual
From: Ekkart Rudolph (
Date: Wed Sep 30 1998 - 09:24:56 GMT

The originator of this message is responsible for its content.
-----From Ekkart Rudolph <> to mscnews -----

Paul Baker wrote:

> Dear MSC folks,
> I think there is a problem regarding the instance-oriented textual
> grammar for the shared
> inline ‘alt’ and ‘par’ expressions (section 5.3 of Z.120), which:
> (2) makes it impossible to define the semantics for alt and par
> expressions using the
> instance-oriented grammar. The reason for this is that it is not
> possible (in some cases)
> given the information provided to determine which events, existing on
> different instances,
> are associated with different alt or par arguments. And in fact
> whether events are
> indeed associated with the same alt or par expression.

Dear Paul,
can you give a simple example? I cannot see immediately your point because
of the shared construct.

Apart from that, I do not like so much the terminology 'instance oriented' and
'event oriented' grammar in MSC-96. In fact, my idea was to include the
'instance oriented' representation of MSC-92 within the new 'event oriented' representation.
(since message inputs may appear before corresponding message outputs within this
'event oriented' grammar)

Unfortunately, because of upward compatability there still remained this
<old instance head statement>. Apart from that, I would rather distinguish between
<shared event> - and <multi instance event> representation (e.g. with respect to
conditions and inline expressions). I must admit that the <shared event> - representation
in some parts (e.g. inline expression) resembles the original 'instance oriented'
representation, in order to avoid the obscuring mixing of events on different instances
within operator expressions.

Best regards!

Dr. Ekkart Rudolph phone: +49 89 289 25361
Technische Universitaet Muenchen fax: +49 89 289 28183
Institut fuer Informatik, email:
c/o Lehrstuhl Prof. Broy
Arcisstrasse 21
D - 80290 Muenchen

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