[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] RE: Two quick questions regarding restriction in XML Schema
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@C...] > Sent: Fri 5/17/2002 9:13 AM > To: Dare Obasanjo > Cc: Eddie Robertsson; Nada Reinprecht; xml-dev@l... > Subject: RE: 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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