Group qualified inverse attributes?

[Phil Spiby]

Pascal,

I wouldn't dare propose something which was not upwards compatibile with
the current standard ;-)

My suggested syntax is a little simpler that yours:
INVERSE
   inv_att : SET[1:?] OF sub FOR sup1.att;

This would require that sup1 is in the same sub/sup graph as sub.

Your proposal requires that the entity before the group qualifier is the
same as before the FOR keyword.

Phil


> -----Original Message-----
> From: owner-wg11 at steptools.com 
> [mailto:owner-wg11 at steptools.com] On Behalf Of Pascal Huau
> Sent: 15 July 2002 14:35
> To: Phil.Spiby at eurostep.com
> Cc: wg11 at steptools.com
> Subject: Re: Group qualified inverse attributes?
> 
> 
> Phil,
> 
> For the moment, because of the previous constraint, the 
> attribute names after FOR in Inverse statements are either a 
> name of an own attribute of the referencing entity or the 
> name of an inherited attribute of that entity. As long as 
> this latter syntax remains allowed (for upward compatibility 
> reasons), I have no problem with the proposal.
> 
> I propose that kind of syntax:
> 
> > INVERSE
> >   inv_att : SET[1:?] OF sub FOR sub\sup1.att;
> >
> 
> Regards,
> Pascal Huau
> Association GOSET
> 107,111 avenue Georges Clemenceau
> 92000 Nanterre
> FRANCE
> ----- Message d'origine -----
> De : "Phil Spiby" <esukpc02 at nildram.co.uk>
> À : <wg11 at steptools.com>
> Envoyé : lundi 15 juillet 2002 15:26
> Objet : Group qualified inverse attributes?
> 
> 
> > Expressarios,
> >
> > The ballot comment NSF2 from Norway (given below) was accepted.
> >
> > NSF2: In TC2 a restriction has been introduced concerning 
> valid types 
> > for INVERSE: "The name of the explicit attribute in the entity 
> > defining the direct relationship shall be unique within the 
> > subtype/supertype graph of that entity." This restriction is an 
> > unnecessary limitation. The attribute could easily be 
> qualified to the 
> > correct attribute by the name of the supertype using a group 
> > qualifier.
> > ACCEPTED: Will need to introduce new syntax for inverse 
> attributes to
> > allow such qualification, i.e. inverse inv: sub for sup1/attrib
> >
> > On verifying this syntax change I have noticed that the comment and 
> > the accepted resolution were wrong. It is not possible to 
> use a group 
> > qualifier in this way. According to EXPRESS the identifier after a 
> > group qualifier shall be the name of an entity, in the case of the 
> > accepted resolution an attribute identifier is given after 
> the group 
> > qualifier. I guess we could change the accepted resolution 
> to allow a 
> > attribute qualifier and have: INVERSE
> >   inv : sub FOR sup1.attrib;
> >
> > Suggestions etc.
> >
> > Phil.
> >
> > PS The reason for this comment was because TC2 had 
> explicitly banned 
> > inverses to ambiguous attribute identifiers (This I think 
> was a good 
> > move but other obviously didn't!). This resolution was an 
> attempt to 
> > allow these references again, but this time to ensure there was no 
> > ambiguity by de-referencing the attribute identifier in the 
> context of 
> > the entity in which it was declared.
> >
> 
>