Subject: MSC News: Discussions on future MSC
From: Oystein Haugen (etooha#eto.ericsson.se)
Date: Mon Aug 11 1997 - 13:53:24 GMT
The originator of this message is responsible for its content.
-----From "Oystein Haugen"<etooha#eto.ericsson.se> to mscnews -----
Dear MSC friends
As stated in the Geneva minutes of the Study Group 10 meeting, Question
9, The Rapporteur is supposed to initiate some discussion on the
distribution list concerning some of the outstanding issues of MSC in
order to receive comments and suggestions. The comments and suggestions
will then be input to the standardization work.
According to the minutes there are two issues on which we seek comments
on the distribution list already now in August. These are:
1. Graphical notation for General Order Relation
2. Gate endpoint constraints.
Concerning the first issue on the graphical notation on General Order
Relation, this issue was raised by the former Rapporteur, now assoicate
rapporteur for maintenance, Ekkart Rudolph in a contribution to Geneva.
The issue is that the definition of the graphics of General Order
Relation as found in MSC-96 (Z.120) is ambiguous in some instances. The
problem is that the start and end of a relation cannot always be
identified when the relation connects output events since the event
itself has only a point as symbol. The point cannot be distinguished
from the intersection of a message (or general order relation) with an
If you found my above explanation still difficult to understand, do not
panic. Graphic problems are often difficult to explain in words.
Therefore Ekkart Rudolph has provided a splendid example of the problem
together with a series of suggestions to solve the ambiguity. The file
has been distributed earlier on the distribution list, but up until now
I have not seen any discussion about it. Ekkart will also bring the
issue up in the workshop which he will conduct at the 8th SDL Forum in
Paris in September, but we may start the discussion already here.
The example file in postscript will be attached to a mail following this
Gate endpoint constraints were suggested by the current Rapporteur in a
contribution to the Geneva meeting. The suggestion is also covered in a
paper (authored by myself) to be presented at the SDL Forum in
September. Still again, to begin the discussion ahead of time should
only be to the benefit of future MSC.
The issue is that in MSC-96 there is a possibility to have message
gates. A message gate is defined by a message which is output to the
environment/frame or input from it. These points are then connected in
MSCs with references referring to the definition just mentioned. The MSC
references have actual gates from where the messages "continue",
eventually to instances.
The problem is that inside the definition of the MSC there is no way to
describe to which instance the message will eventually go other than by
naming the gates in a creative way.
Inspired by the gatepoint constraints of SDL-92 and by the use of MSC-92
dialects found at one of the companies involved in the Norwegian SISU
project, we suggest a similar construct in MSC. The idea is to have
instances also outside the MSC frame to represent types of instances
which can be the other endpoint of messages going to/from the
In a following mail, the Geneva contribution will be made available in
uuencoded postscript form to the members of the distribution list.
-- ------------------------ Oystein Haugen, Ericsson as. , P.O. box 34, N-1361 Billingstad, Norway Tel: +47 66 84 23 46 Fax: +47 66 98 28 20 E-mail: etooha#eto.ericsson.se
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