Subject: Re: MSC-News: Problem with instance-oriented - shared in-line expression textual
From: Oystein Haugen (oystein.haugen#ericsson.no)
Date: Thu Sep 24 1998 - 10:34:40 GMT
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-----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>
> 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
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.
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
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, 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
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