SEDS for ISO 10303-11

David Price david.price at eurostep.com
Thu Nov 29 09:06:45 EST 2001 

Jochen,

Thanks, I think I understand the SEDS now. For any case where a variable has
a declared type, assignments of a value of the variable to other variables
or attributes shall maintain the original type so that TYPEOF can return the
original type too.

A clarification question... given the BAG/SET example, if I add 2 as a new
member of the x that has been assigned the SET [1,2,3] would you expect only
BAG to be returned by TYPEOF? I assume so. That means it's more than just
assignment that is affected. I think it means that the type of the assigned
value must be maintained and then every operation that changes the value
must check if the change causes a change in any of its types.

I imagine this adds complexity to implementations but as I said, I'll leave
that issue to others.
Cheers,
David

> -----Original Message-----
> From: Jochen Haenisch [mailto:Jochen.Haenisch at epmtech.jotne.com]
> Sent: 2001 November 29 13:48
> To: 'david.price at eurostep.com'
> Cc: 'WG11 exploder'; Hans Karsten Dahl
> Subject: RE: SEDS for ISO 10303-11
>
>
> David,
>
> if TYPEOF is supposed to work like is_kind_of already - great.
> Then we only
> need to polish the describing text in the LRM. This is indeed what I hoped
> for!
>
> NUMBER is only a special case for which TYPEOF also should return
> the actual
> type of the parameter value (not only the declared one).
>
> Same for aggregates, but only if they are really assigned a different type
> of aggregate:
>   LOCAL
>     x : BAG OF INTEGER;
>     y: SET OF INTEGER := [1,2,3];
>   END_LOCAL;
>   x := y;
> In this case TYPEOF(x) should return ['SET', 'BAG'], not only ['BAG'].
>
> If you have:
>   LOCAL
>     y: BAG OF INTEGER := [1,2,3];
>   END_LOCAL;
> TYPEOF(x) should only return ['BAG'].
>
> The assignment is the point! Only then the program can really
> trace the type
> of an instance.
>
> I hope that makes my issue clearer?!?
>
> Regards, Jochen
> > -----Original Message-----
> > From:	David Price [SMTP:david.price at eurostep.com]
> > Sent:	29. november 2001 14:28
> > To:	Jochen Haenisch
> > Cc:	'WG11 exploder'; Hans Karsten Dahl
> > Subject:	RE: SEDS for ISO 10303-11
> >
> > Jochen,
> >
> > When you said it didn't apply to BAG and SET I assumed NUMBER
> was the only
> > case. The is_instance_of and is_kind_of only apply to entity instances,
> > not
> > simple data types, in SDAI so it's not quite the same thing. Actually, I
> > think TYPEOF already works as you want in the case of entity
> instances. It
> > seems you are asking for simple types, but not aggregation types, to be
> > treated the same as entity instances because you believe all data values
> > will be represented as objects and therefore can maintain the
> data type of
> > whatever was most recently assigned. Is that right?
> >
> > Sorry to be a pain but I seem to be confused as to the extent of the
> > request
> > in this SEDS.
> > Thanks,
> > David
> >
> > > -----Original Message-----
> > > From: Jochen Haenisch [mailto:Jochen.Haenisch at epmtech.jotne.com]
> > > Sent: 2001 November 29 13:05
> > > To: 'david.price at eurostep.com'
> > > Cc: 'WG11 exploder'; Hans Karsten Dahl
> > > Subject: RE: SEDS for ISO 10303-11
> > >
> > >
> > > Daivd,
> > >
> > > yes, I do mean that this applies to more than NUMBER! Think of an
> > example
> > > with PERSON and subtypes MAN and WOMAN. That would make more sense.
> > > If I am not mistaken, SDAI offers the required functionality in
> > > is_instance_of/is_kind_of.
> > >
> > > Regards, Jochen.
> > >
> > > > -----Original Message-----
> > > > From:	David Price [SMTP:david.price at eurostep.com]
> > > > Sent:	29. november 2001 13:57
> > > > To:	Jochen Haenisch
> > > > Cc:	'WG11 exploder'; Hans Karsten Dahl
> > > > Subject:	RE: SEDS for ISO 10303-11
> > > >
> > > > Hi Jochen,
> > > >
> > > > My two kroner...
> > > >
> > > > I do agree NUMBER is a strange datatype but I'm not sure that means
> > the
> > > > relationship between it and a specialiation of it should be treated
> > > > differently OR do you mean for this to apply to more than NUMBER?
> > > >
> > > > > An implementation will nontheless keep track of the actual type of
> > an
> > > > > object. So, why not give the user the (necessary) possibility to
> > > > > query this?
> > > >
> > > > I'm not sure it's a good idea to assume this for all
> implementations.
> > > > Functionally, NUMBER is treated like REAL in many of the 20s
> > > series parts
> > > > so
> > > > implementations may lose the distinction. However, I've not
> > implemented
> > > > this
> > > > myself so will leave that issue to others.
> > > >
> > > > Cheers,
> > > > David
> > > >
> > > > > -----Original Message-----
> > > > > From: Jochen Haenisch [mailto:Jochen.Haenisch at epmtech.jotne.com]
> > > > > Sent: 2001 November 29 12:24
> > > > > To: 'david.price at eurostep.com'
> > > > > Cc: 'WG11 exploder'; Hans Karsten Dahl
> > > > > Subject: RE: SEDS for ISO 10303-11
> > > > >
> > > > >
> > > > > David,
> > > > >
> > > > > no, the point is not to detect that a BAG is a SET based on the
> > > > > characteristics of its population. This is beyond the limits, but
> > not
> > > > very
> > > > > much. The point is to have a possibility to query which type of
> > value
> > > > has
> > > > > intentionally been assigned to a parameter.
> > > > >
> > > > > Building on the previous example one could imagine the following
> > > > > situation:
> > > > >
> > > > >  LOCAL
> > > > >    x : NUMBER;
> > > > >    y: REAL := 1.0;
> > > > >    z: INTEGER := 2;
> > > > >  END_LOCAL;
> > > > >
> > > > >  IF (...) THEN x:=y;
> > > > >  ELSE x:=z;
> > > > >  END_IF;
> > > > >
> > > > >  IF ('REAL' IN TYPEOF(x)) THEN ...; END_IF;
> > > > >
> > > > > Even though this may not be the most convincing real life
> example, I
> > > > hope
> > > > > you see the usefulness of TYPEOF returning the type of the value
> > that
> > > > has
> > > > > been assigned to it. How else could one treat x differently
> > > based on the
> > > > > type that it is carrying around?
> > > > > An implementation will nontheless keep track of the actual type of
> > an
> > > > > object. So, why not give the user the (necessary) possibility to
> > > > > query this?
> > > > >
> > > > > Best regards, Jochen.
> > > > >
> > > > > > -----Original Message-----
> > > > > > From:	David Price [SMTP:david.price at eurostep.com]
> > > > > > Sent:	29. november 2001 12:13
> > > > > > To:	Jochen Haenisch
> > > > > > Cc:	'WG11 exploder'
> > > > > > Subject:	RE: SEDS for ISO 10303-11
> > > > > >
> > > > > > Jochen,
> > > > > >
> > > > > > I'm not sure I like the idea that the datatype of something
> > > > > depends on its
> > > > > > instantiated value. TYPEOF is a datatype, not data value,
> > > > > function so I'm
> > > > > > a
> > > > > > bit confused. Can you elaborate on why you want this change? Is
> > this
> > > > > > example
> > > > > > any different from x being declared as a BAG that happens to be
> > > > > > instantiated
> > > > > > with non-duplicate members and so you want TYPEOF to return SET?
> > > > > >
> > > > > > Hope my question makes sense. It's basically, how far would
> > > you expect
> > > > > > this
> > > > > > proposal to go?
> > > > > >
> > > > > > Cheers,
> > > > > > David
> > > > > >
> > > > > > > -----Original Message-----
> > > > > > > From: owner-wg11 at steptools.com
> > [mailto:owner-wg11 at steptools.com]On
> > > > > > > Behalf Of Jochen Haenisch
> > > > > > > Sent: 2001 November 29 09:02
> > > > > > > To: 'seds at cme.nist.gov'
> > > > > > > Cc: 'WG11 exploder'
> > > > > > > Subject: SEDS for ISO 10303-11
> > > > > > >
> > > > > > >
> > > > > > > Please, consider the SEDS report that is included below.
> > > > > > > Best regards, Jochen Haenisch.
> > > > > > >
> > > > > > >  <<SEDS_Express_20011129.txt>>
> > > > > > >
> > > > > > > ____________________________________________________________
> > > > > > > Jochen Haenisch			E-mail:
> > > > > > > Jochen.Haenisch at epmtech.jotne.com
> > > > > > > EPM Technology AS		Home of the EXPRESS Data Manager
> > > > > > > P.O Box 6629 Etterstad		Tel: Int + 47 23 17 17 26
> > > > > > > N-0607 Oslo				Fax: Int +
> 47 23 17 17 01
> > > > > > > Norway					Web:
> > > > > > > http://www.epmtech.jotne.com
> > > > > > >
> > > > > > >

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