Only one TOTAL_OVER

[Phil Spiby]

Peter,

The argument for this was that a subtype constraint allows clearer
specification of the rational for the semantics. Your example should, I
believe, be re-written:

SUBTYPE_CONSTRAINT gender_constraint FOR person;
  TOTAL_OVER(female, male);
END_SUBTYPE_CONSTRAINT;

SUBTYPE_CONSTRAINT citizenship_constraint FOR person;
  TOTAL_OVER(alien, citizen);
END_SUBTYPE_CONSTRAINT;

I know EXPRESS was never intended to enforce good modelling, and it shows
from a number of models!!, but in this case we decided that we would have
try!

Phil


> -----Original Message-----
> From: owner-wg11 at steptools.com [mailto:owner-wg11 at steptools.com]On
> Behalf Of Wilson, Peter R
> Sent: Thursday, May 09, 2002 8:00 PM
> To: 'wg11'
> Cc: Wilson, Peter R
> Subject: DAM: Only one TOTAL_OVER
>
>
>     The DAM allows a maximum of one TOTAL_OVER constraint in a
> SUBTTPE_CONSTRAINT. Is there any good reason why it should not allow
> multiple TOTAL_OVERs?
>
>     For example, our old friend person being either male or female and
> either alien or citizen. At the moment this has to be done like (ignoring
> any syntax errors):
> SUBTYPE_CONSTRAINT sc1 FOR person;
>   TOTAL_OVER(female, male);
> END_SUBTYPE_CONSTRAINT;
> SUBTYPE_CONSTRAINT sc2 FOR person;
>   TOTAL_OVER(alien, citizen);
> END_SUBTYPE_CONSTRAINT;
>
>     Why not allow
> SUBTYPE_CONSTRAINT sc12 FOR person;
>   TOTAL_OVER(female, male);
>   TOTAL_OVER(alien, citizen);
> END_SUBTYPE_CONSTRAINT;
>
> Peter W.
>
> Dr Peter R. Wilson
> Boeing Commercial Airplanes
> PO Box 3707, MS 6H-AF, Seattle, WA 98124-2207
> (Package Delivery: MS 6H-AF, 1601 E. Valley Frontage Road,
> Renton, WA 98055)
> Tel: (425) 237-3506, Fax: (425) 237-3428
> Email: peter.r.wilson at boeing.com
> --------------------------------
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>