Necessity of Part 25 change supporting ONEOF?

[Lothar Klein]

David,

The problem here is more a political.
Do we just want to map EXPRESS with UML or do
we want to make STEP data models available in UML?
In the first case your proposals sounds good.
In the second case however it makes little sense since
the ONEOF and ANDOR stuff is more or less totally broken
in STEP data models. In actual APs and IRs there exist
soooo many valid but wrong ANDOR combinations that it
makes little sense to map this to UML.

My proposal is to 
- make EXPRESS rich enough to model "weak ONEOFs" 
- go through all IRs and APs and use this new feature
- and then to map STEP with UML

Am I the only one who thinks we should fix STEP?

Lothar



David Price wrote:
> 
> Folks,
> 
> I've thought a little more about this and believe that to allow the correct
> EXPRESS SUPERTYPE semantics to be somehow represented in UML we should do
> the following:
> 
> 1 - If there is no SUPERTYPE constraint, specify the UML overlapping
> constraint.
> 2 - If there is exactly one ONEOF that covers all subtypes of an entity
> type, specify the UML disjoint contraint.
> 3 - In all other cases where any SUPERTYPE constraint is specified, specify
> the UML overlapping constraint.
> 
> 1 and 2 should be clear. I'm proposing 3 because it allows for the overlaps
> that do occur in EXPRESS to be represented in the UML model. It does also
> allow more combinations in the UML than are legal in the EXPRESS but we
> can't allow fewer combinations - which is what happens if you specify
> disjoint (or nothing since disjoint is the default). We'll have to assume
> that when people create data, the AP or a usage guide they are using to
> explain what's legal will result in correct data generation. Perhaps as UML
> constraints are harmonized with EXPRESS constraints we can add more to the
> mappings in the future.
> 
> Anyone disagree with this approach? Anyone agree?
> Thanks,
> David
> 
> IBM Corporation
> 5300 International Blvd.
> N. Charleston, SC 29418, USA
> dmprice at us.ibm.com
> Phone : +1 (843) 760-4341   Fax : +1 (843) 760-3349
> Oooo.
> (UNC)
>  ) /
> (*/
> 
> David Price/Bethesda/IBM at IBMUS@steptools.com on 02/16/2001 12:57:02 PM
> 
> Sent by:  owner-wg10 at steptools.com
> 
> To:   wg10 at steptools.com, xmlsc4 at nist.gov, wg11 at smiling.net
> cc:
> Subject:  Re: Necessity of Part 25 change supporting ONEOF?
> 
> Folks,
> 
> If we were going to do anything about this I'd propose something like the
> following (or as I said, do nothing):
> 
> PROPOSAL - For each EXPRESS entity data type visible in the context of the
> mapping that has subtypes visible in the context of the mapping and within
> which no SUPERTYPE constraint is specified, a UML "overlapping" constraint
> shall appear in the UDS. For each EXPRESS entity data type that is a
> subtype of the EXPRESS entity data type within which no SUPERTYPE
> constraint is specified, include the UML Generalization representing that
> EXPRESS subtype relationship in the UML "overlapping" constraint created
> for the EXPRESS supertype.
> 
> Thanks,
> David
> 
> IBM Corporation
> 5300 International Blvd.
> N. Charleston, SC 29418, USA
> dmprice at us.ibm.com
> Phone : +1 (843) 760-4341   Fax : +1 (843) 760-3349
> Oooo.
> (UNC)
>  ) /
> (*/
> 
> David Price/Bethesda/IBM at IBMUS@steptools.com on 02/16/2001 11:43:53 AM
> 
> Sent by:  owner-wg10 at steptools.com
> 
> To:   wg10 at steptools.com, xmlsc4 at nist.gov, wg11 at smiling.net
> cc:
> Subject:  Necessity of Part 25 change supporting ONEOF?
> 
> Part 25/EXPRESS/UML Folks,
> 
> At the Charleston ISO meeting I was given the following change to make to
> Part  25:
> 
> "5 - Make EXPRESS ONEOF an explicit UML disjoint constraint between
> subclasses of a
> common UML Class representing an EXPRESS entity that is a supertype when
> specified
> in the EXPRESS supertype constraint."
> 
> After reviewing the UML 1.3 spec further I think this change is not
> necessary. In fact, if we do anything we need to add "overlapping" in the
> case where no SUPERTYPE constraint is specified.
> 
> Here's what UML 1.3 says about : Generalization
> 
> A generalization is a taxonomic relationship between a more general element
> and a more specific element. The more specific element is fully consistent
> with the more general element (it has all of its properties, members, and
> relationships) and may contain additional information. In the metamodel, a
> Generalization is a directed inheritance relationship, uniting a
> GeneralizableElement with a more general GeneralizableElement in a
> hierarchy. Generalization is a subtyping relationship (i.e., an Instance of
> the more general GeneralizableElement may be substituted by an Instance of
> the more specific  GeneralizableElement). See Inheritance for the
> consequences of Generalization relationships.
> 
> Here are two of the Standard Constraints that can be applied. Note that
> "disjoint" (i.e. ONEOF) is the default!
> 
> disjoint
> 
> Specifies a constraint applied to a set of generalizations, indicating that
> instance of the parent may be an instance of no more than one of the
> given children within the set of generalizations. This is the default
> semantics of generalization.
> 
> overlapping
> 
> Specifies a constraint applied to a set of generalizations, indicating that
> an instance of one child may be simultaneously an instance of another
> child in the set (but there is no guarantee that such an instance will
> actually exist).
> 
> Opinions on what do to? I think either 1) do nothing or 2) add overlapping
> if no supertype constraint at all, but let's not try and
> figure out the complete set of permutations.
> 
> Thanks,
> David
> 
> IBM Corporation
> 5300 International Blvd.
> N. Charleston, SC 29418, USA
> dmprice at us.ibm.com
> Phone : +1 (843) 760-4341   Fax : +1 (843) 760-3349
> Oooo.
> (UNC)
>  ) /
> (*/

-- 
// Lothar Klein, LKSoftWare GmbH
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