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I hope to finish the report soon, of course (couple of days at most), I
will try to announce it on the list, and to you people who have helped me
immensely.
I have one question regarding extension:
can we define the following types
type Book -> (Title, Author+)
type Book1 extends Book -> (Title, Author+, Title)
Note: If the above type definitions are valid, then I am afraid, there is
a problem with the framework of subsumption. I think subsumption will be
able to capture only restricted subset of extensions allowed in W3C's
XML-Schema. I am quite confident of my conclusions. (The above extension
cannot be captured using subsumption)
thanks and regards - murali.
On Fri, 17 May 2002, Dare Obasanjo wrote:
> From the little I know of W3C XML Schema, the answer to all your questions is Yes.
>
> I'd love to read this report when you are done with it. Will it be online somewhere?
>
> -----Original Message-----
> From: Murali Mani [mailto:mani@CS.UCLA.EDU]
> Sent: Fri 5/17/2002 9:13 AM
> To: Dare Obasanjo
> Cc: Eddie Robertsson; Nada Reinprecht; xml-dev@lists.xml.org
> Subject: RE: [xml-dev] Two quick questions regarding restriction in XML Schema
>
>
>
>
> My question was this:
> We have type definitions,
>
> type Book (block="restriction") -> (Title, Author*)
> type Book1 restricts Book -> (Title, Author, Author)
>
> and element declaration
> <element book type="Book">
>
> So which of the two following documents are valid?:
> <book>
> <title>XYZ</title>
> <author>ABC</author>
> <author>DEF</author>
> </book>
>
> and
>
> <book xsi:type="Book1">
> <title>XYZ</title>
> <author>ABC</author>
> <author>DEF</author>
> </book>
>
> I think the answer is the first document is valid, whereas the second one
> is not, because of the reason which Dare gives second. This is clear.
>
> Now, one more question on restriction:
>
> suppose we defined
> type Book (final="restriction") -> Title, Author*
> now we cannot define type Book1 as above, correct??
>
> also let us assume the element declaration as above
> <element book type="Book">
>
> Consider the following document:
> <book>
> <title>XYZ</title>
> <author>ABC</author>
> <author>DEF</author>
> </book>
>
> The above document is valid, right?
>
> I will tell you what I am trying to understand: "I have seen two
> frameworks trying to explain subtyping in XML - one is in XDuce using
> inclusion, and other is a framework known as subsumption. I am trying to
> analyze them. These questions help me in understanding. I am presently
> writing a "short" report (presently 6 pages, I believe it will be less
> than 10 pages) analyzing the various subtyping schemes for XML."
>
> thanks and regards - murali.
>
> On Fri, 17 May 2002, Dare Obasanjo wrote:
>
> > The validity first document is valid while the second isn't but not
> > for the reasons you suppose. The second one is invalid because no type
> > definition exists for a type named "Book1". :)
> >
> > However, assuming that a Book1 type one existed and it was a valid
> > restriction of Book then you are correct that the document is invalid.
> > According to
> >
> > Validation Rule: Element Locally Valid (Element) [0] 4 If there is an
> > attribute information item among the element information item's
> > [attributes] <http://www.w3.org/TR/xml-infoset/#infoitem.element>
> > whose [namespace name]
> > <http://www.w3.org/TR/xml-infoset/#infoitem.attribute> is identical to
> > http://www.w3.org/2001/XMLSchema-instance and whose [local name]
> > <http://www.w3.org/TR/xml-infoset/#infoitem.attribute> is type, then
> > all of the following must be true: 4.1 The ·normalized value· of
> > that attribute information item must be ·valid· with respect to the
> > built-in QName
> > <http://www.w3.org/TR/2001/REC-xmlschema-2-20010502/datatypes#QName>
> > simple type, as defined by String Valid (§3.14.4); 4.2 The ·local
> > name· and ·namespace name· (as defined in QName Interpretation
> > (§3.15.3)), of the ·actual value· of that attribute information
> > item must resolve to a type definition, as defined in QName resolution
> > (Instance) (§3.15.4) -- [Definition:] call this type definition the
> > local type definition; 4.3 The ·local type definition· must be
> > validly derived from the {type definition} given the union of the
> > {disallowed substitutions} and the {type definition}'s {prohibited
> > substitutions}, as defined in Type Derivation OK (Complex) (§3.4.6)
> > (if it is a complex type definition), or given {disallowed
> > substitutions} as defined in Type Derivation OK (Simple) (§3.14.6)
> > (if it is a simple type definition).
> >
> > [0] http://www.w3.org/TR/2001/REC-xmlschema-1-20010502/#cvc-elt
>
>
>
>
>
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