Subject: Re: MSC-News: Problem with instance-oriented - shared in-line expression textual
From: UK496 Paul Baker (paul#bae231.comm.mot.com)
Date: Fri Sep 25 1998 - 10:56:56 GMT
The originator of this message is responsible for its content.
-----From UK496 Paul Baker <paul#bae231.comm.mot.com> to mscnews -----
Hi Oystein,
> My principal opinion of course is that we need no textual grammar at
> all. A textual grammar can be derived easily from the graphical one and
> thereby we would not have any consistency problems. It has been argued
> that the graphical grammar is not equally precise. This is not true with
> respect to the simple sequencing of symbols. Where it is not entirely
> precise is regarding the concrete graphics, but for that any textual
> syntax says nothing anyway.
> The biggest obstacle for removing the textual grammar altogether is the
> need (?) to be backward compatible with earlier textual descriptions. I
I agree. One suggestion (from Clive) would be to define a mapping
function
which maps the event-oriented grammar onto the instance-oriented
grammar. Then
consistency between grammars would not be a problem, but correctness of
the mapping
function would.
> As with Claim (2) I wonder _why_ you would like to use the
> instance_oriented grammar for a formal semantics.
I do not want to define a formal semantics based upon the
instance-oriented. However,
if somebody did wish to do so this is not possible at present.
Regards
Paul.
Oystein Haugen wrote:
>
> The originator of this message is responsible for its content.
> -----From Oystein Haugen <oystein.haugen#ericsson.no> to mscnews -----
>
> UK496 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:
> >
> > (1) does not follow the graphical grammar. <snip>
> >
> > (2) makes it impossible to define the semantics for ‘alt’ and ‘par’
> > expressions using the instance-oriented grammar. <snip>
>
> <snip>
>
> > Any comments?
> >
>
> According to my brief review of your claim (1), I believe you are right.
> There is a (uniintended) discrepancy between the graphical and textual
> grammars.
>
> As with Claim (2) I wonder _why_ you would like to use the
> instance_oriented grammar for a formal semantics. Still we should make
> sure that there are no ambiguities regarding this.
>
> am not certain how big this need is. Other languages (such as Word or
> Frame) seem to be very lenient when it comes to being backward
> compatible w.r.t. the storage format. As long as there is a utility to
> read / convert old descriptions, the new format may vary considerably
> from the former.
>
> Opinions are highly welcome.
>
> 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 Mob: +47 913 90 914
> E-mail: oystein.haugen#ericsson.no
>
> -----End text from Oystein Haugen <oystein.haugen#ericsson.no> to mscnews -----
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