RE: Allowable schema representations

[Aleksandar Milanovic <am...@galdosinc.com>]

Actually, MSXML 4.0 complains about this schema. It says that elements with
the same name and in the same scope have to be of the same type. In this
case, type C2 contains two A elements of different types, hence the schema
is invalid.

Strangely, I too couldn't find anything in the XML Schema spec. about this.

Alex

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  -----Original Message-----
  From: Bob Schloss [mailto:rschloss@us.ibm.com]
  Sent: Wednesday, July 31, 2002 10:15 AM
  To: xerces-j-user@xml.apache.org
  Subject: Re: Allowable schema representations


  W3C XML Schema language permits different content models for elements with
the same name, as long as the validator can unambiguously determine which
content model applies. Your examples are legal.

  Bob Schloss
  XML/XSL Transformational Systems
  IBM Thomas J. Watson Research Center
  Yorktown Heights, New York, USA



  Please respond to xerces-j-user@xml.apache.org

  To: xerces-j-user@xml.apache.org
  cc:
  Subject: Allowable schema representations



  If I define an XML schema as follows:

  <?xml version="1.0" encoding="UTF-8"?>
  <!-- strange.xsd -->
  <xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"

          targetNamespace="http://localhost/strange"
          xmlns="http://localhost/strange"
          elementFormDefault="qualified">
  <xsd:complexType name="C1">
  <xsd:sequence>
    <xsd:element name="A" type="xsd:string"/>
    </xsd:sequence>
  </xsd:complexType>
  <xsd:complexType name="C2">
    <xsd:sequence>
    <xsd:element name="A" type="C1"/>
    <xsd:element name="A" type="xsd:string"/>
  </xsd:sequence>
  </xsd:complexType>
  <xsd:element name="A" type="C2"/>
  </xsd:schema>


  then an instance document looks like

  <?xml version="1.0" encoding="UTF-8"?>
  <!-- strange.xml -->
  <A xmlns="http://localhost/strange"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://localhost/strange strange.xsd">
  <A>
  <A>foo</A>
  </A>
  <A>bar</A>
  </A>


  Is there anything inherently wrong with having an "A" element used in
  many different ways? Xerces will certainly validate the document OK, and
  I couldn't find anything in the xml-schema spec that invalidates this.
  It looks strange to me, as I don't think you could have defined this
  structure using a DTD. Does anyone have a view on this?

  cheers

  Loz


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