RE: MSC-News: Incomplete messages


Subject: RE: MSC-News: Incomplete messages
From: Jan Docekal (jan.docekal#telelogic.se)
Date: Thu Aug 20 1998 - 11:17:48 GMT


The originator of this message is responsible for its content.
-----From Jan Docekal <jan.docekal#telelogic.se> to mscnews -----

Dear Dimitry,

I must admit that i missed your point first time i read your question.

It is my opinion that the /* input event */ should not be present in the
example below. My opinion is however contradicted to some extent by the
example "6.21 High-Level MSC with alternate comosition, msc message
lost", which contains the same construct as the example below.

My opinion is however that both the examples are wrong. What happens if
a message is lost to an instance that is not present in the current msc?
Another problem is that there seems to be no natural point where the
lost messages should be "recieved". In the example below the lost
message is "recieved" between conditions, but what happens if other
messages where exchanged between Initiator and Responder. It is
impossible to show graphically that an event is "not recieved" between
two messages at the Responder. To mee it seems quite natural that if the
mesage is lost, it is per definition not recieved by the intended
reciever (and then there should be no evidence of such an activity in
the textual representation of the diagram).

I would like other members to give their opinions (or even better
knowledge) in this matter, since I seem to be unable to answer simple
questions on the first try:-)

Cheers,
Jan.

> -----Original Message-----
> From: Dmitry Zhukov [SMTP:dmjr#ispras.ru]
> Sent: den 20 augusti 1998 12:41
> To: Jan Docekal
> Cc: mscnews#sdl-forum.org
> Subject: RE: MSC-news: Incomplete messages
>
> The originator of this message is responsible for its content.
> -----From Dmitry Zhukov <dmjr#ispras.ru> to mscnews -----
>
> Dear Jan,
>
> On Thu, 20 Aug 1998, Jan Docekal wrote:
>
> > It is correct.
> >
> > Possible interpreatations follows:
> >
> > Instance A sends message M to instance B. After M is sent, but
> before M
> > is recieved, B is (inexpectedly) terminated. Message B still knows
> that
> > it was on its way to B, but can no longer find it.
> >
> > I think that the possibility to specify the reciever of the lost
> > messages is most useful when making a trace of a system execution,
> > rather than when specifying system behaviour.
>
> I agree with you that specifying the receiver of lost messages
> is often useful. It is unclear to me, why an *input event* is
> specified for the lost message. I think that if both output and
> input events are known for a message it is better to use a general
> message rather then a lost.
>
> Best regards,
> Dmitry.
>
> > > I have a question of incomplete message events in MSC'96.
> > > Consider the following example from Recommendation Z.120,
> > > section 6.6:
> > >
> > > msc failure; inst Initiator, Responder;
> > > instance Initiator;
> > > condition Disconnected shared all;
> > > in ICONreq from env;
> > > set T;
> > > out ICON to lost Responder; /* output event */
> > > condition Wait_For_Resp shared all;
> > > timeout T;
> > > out IDISinf to env;
> > > condition Disconnected shared all;
> > > endinstance;
> > >
> > > instance Responder;
> > > condition Disconnected shared all;
> > > in ICON from Initiator; /* input event */
> > > condition Wait_For_Responder shared all;
> > > condition Disconnected shared all;
> > > endinstance;
> > > endmsc;
> > >
> > > As described in section 4.3,
> > >
> > > An incomplete message is a message which is either an output
> > > (where the input is lost) or an input (where the output is
> > > unknown)
> > >
> > > But in the example above the input is specified for the
> > > lost message ICON. How should one understand this example ?
> > > Is it correct ?
>
>
> -----End text from Dmitry Zhukov <dmjr#ispras.ru> to mscnews -----
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-----End text from Jan Docekal <jan.docekal#telelogic.se> to mscnews -----
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