OASIS Mailing List ArchivesView the OASIS mailing list archive below
or browse/search using MarkMail.

 


Help: OASIS Mailing Lists Help | MarkMail Help

ubl-cmsc message

[Date Prev] | [Thread Prev] | [Thread Next] | [Date Next] -- [Date Index] | [Thread Index] | [Elist Home]


Subject: RE: [ubl-cmsc] restriction and extension are both subclassing


I agree that extension of a base type can be described as specialization. I heartily disagree that the resulting type has a value set that is a subset of that of the base type. Can you can provide an example of values valid in the base type but not in the extended type?
 
Matt
-----Original Message-----
From: Burcham, Bill [mailto:Bill_Burcham@stercomm.com]
Sent: Thursday, May 02, 2002 1:49 AM
To: 'Eduardo Gutentag'
Cc: 'ubl-cmsc@lists.oasis-open.org'
Subject: RE: [ubl-cmsc] restriction and extension are both subclassing

Maybe these two references will help:

(From the category theory perspective) Start at section 2.3 of this paper.  There are two examples in that section of specialization by adding attributes (properties) to the subtypes -- and the explanation is from the set-theoretic perspective.

(From Entity-Relationship Modeling perspective) Start at slide 56 in this presentation.

To your point about the value of this "pure theory analysis" -- Matt G. presented an alternative Specialization Architecture in the CMSC today -- the one described in his recent paper (Schema Adjunct Framework + Schematron).  As a motivator for the value of that architecture, Matt said essentially "restriction and extension are two very different things and the way XSD tries to treat them both as derivation is just wrong -- so we shouldn't use XSD".  Sorry I didn't include that context with my post, but as a rebuttal argument I'd say it isn't just "pure theory analysis" -- I'd say instead that it is rebuttal.

-----Original Message-----
From: Eduardo Gutentag [mailto:eduardo.gutentag@sun.com]
Sent: Wednesday, May 01, 2002 5:47 PM
To: Burcham, Bill
Cc: 'ubl-cmsc@lists.oasis-open.org'
Subject: Re: [ubl-cmsc] restriction and extension are both subclassing


> "Burcham, Bill" wrote:
>
> Since I couldn't get this thought out in the conference call today, I thought I'd get in into the record this way:
>
> From the set-theoretic standpoint, XSD restriction of a simple type and extension of a complex type are the same -- they both define a subset of a base set. To use type terminology, they are both kinds of specialization in the generalization-specialization paradigm.
>
> A simple type is single-valued -- think scalar. When we restrict a scalar type we take away values from its domain. This means that the restricted type has fewer possible values than the original (or base) type. We never add values to the domain. An example of this kind of specialization is: base type Integer, specialized type Whole Number. These are scalars and the set of Whole Numbers is a proper subset of the set of Integers.
>
> A complex type is not single-valued. Instead it is comprised of one or more (simple type or complex type). A complex type can be specialized in two ways: 1) a constituent simple type can be restricted or 2) a property of simple or complex type can be added. In both cases, the new type has fewer possible (compound) values than the original type. Note: that transitivity in the definition of complex type means that there is kind of a third way to specialize a complex type: (3) a constituent complex type can
> be specialized.
>
>

I totally fail to see how a complex type that has been "specialized" by having
a property of either type added has fewer possible values. I just don't see
it. No. Nope. What am I missing?

(and I have to confess that, even if the assertion were true, I fail to see
what is the value added of this kind of pure theory analysis - undoubtedly
the result of a mind that wears glazed eyes at all times and carries an extra
pair just in case...)
--
Eduardo Gutentag               |         e-mail: eduardo.gutentag@Sun.COM
XML Technology Center          |         Phone:  (510) 986-3651
Sun Microsystems Inc.          |


[Date Prev] | [Thread Prev] | [Thread Next] | [Date Next] -- [Date Index] | [Thread Index] | [Elist Home]


Powered by eList eXpress LLC