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Re: looking for help...

From: Michael Case <mecase@ucdavis.edu>
Date: Fri, 18 Jan 2002 13:08:31 -0800
Message-ID: <3C488ECF.BF6881CB@ucdhep.ucdavis.edu>
To: Eddie Robertsson <eddie@allette.com.au>
CC: XSD <xmlschema-dev@w3.org>
Hi,

This seems to go against my conception of XML and I don't know how to
deal with it :-).  In other words, I understand that in XML,
particularly in implementations, document order is not guaranteed, am I
right?  To insist that the XML, therefore, present itself as comments
first, then Rotations, seems to fly in the face of that.

more below...

Thanks again.

Eddie Robertsson wrote:
> 
> Hi Michael,
> 
> > 1)  When you extend a type, is there anything that says the ORDER of the
> > internal elements is implied?  I may not understand enough to ask it
> > properly.
> 
> After looking at your example below I think I know what your problem is. When you extend a type in
> XML Schema it is important to know that the extended types content model will be the base types
> particle sequenced together with the particle defined by the child of the extension element. This
> means that when you extend a sequence group with another element then you're not actually extending
> the base sequence with another element. I use your example to illustrate:
> In your base type you have:
> 
> <xsd:sequence>
>     <xsd:element name = "comment" type = "xsd:string" minOccurs = "0" maxOccurs = "unbounded"/>
> </xsd:sequence>
> 
> And then your extended type look like:
> 
> <xsd:complexType name = "RotationSectionType">
>     <xsd:complexContent>
>           <xsd:extension base = "SectionType">
>               <xsd:sequence>
>                   <xsd:element ref = "Rotation" minOccurs = "0" maxOccurs ="unbounded"/>
>               </xsd:sequence>
>          </xsd:extension>
>     </xsd:complexContent>
> </xsd:complexType>
> 
> When the processor expands this new extended type it will in fact sequence together the two content
> models and create the following type:
> 
> <xsd:complexType name = "RotationSectionType">
>     <xsd:sequence>
>         <xsd:sequence>
>              <xsd:element name = "comment" type = "xsd:string" minOccurs = "0" maxOccurs =
> "unbounded"/>
>         </xsd:sequence>
>         <xsd:sequence>
>             <xsd:element ref = "Rotation" minOccurs = "0" maxOccurs ="unbounded"/>
>         </xsd:sequence>
>     </xsd:sequence>
> </xsd:complexType>

Suppose I really wanted comment elements to be interspersed anywhere
within a bunch of Rotation elements.  Would this do it?

 <xsd:complexType name = "RotationSectionType">
     <xsd:sequence>
             <xsd:element name = "comment" type = "xsd:string" minOccurs
= "0" maxOccurs = "unbounded"/>
             <xsd:element ref = "Rotation" minOccurs = "0" maxOccurs
="unbounded"/>
     </xsd:sequence>
 </xsd:complexType>

Maybe I just can't extend types the way I thought I could...

> 
> As you can see this is the cause of your error. In your instance you have:
> 
>        <RotationSection label = "blah">
>                 <comment xmlns = ""/>
>                <Rotation name = "chfghfhf" theta1 = "0" phi1 = "0" theta2 = "0" phi2 = "0" theta3 =
> "0" phi3 = "0"/>
>                 <comment xmlns = ""/>
>                 <comment xmlns = ""/>
>         </RotationSection>
> 
> but this is not valid since all comment elements (if any are present) need to appear before the
> Rotation elements.
> 
> > 2)  Why does comment want xmlns=""???
> 
> This is because you have elementFormDefault="unqualified" in your schema. In short, what this means
> is that all elements that you have declared locally (nested within complexTypes or groups) cannot be
> qualified with a namespace in the instance document. Since you're using the default namespace
> declaration (xmlns = "http://www.cern.ch/cms/DDL") in the instance this means that all elements
> without a prefix will be qualified by this namespace. However, the processor expects the comment
> element to be unqualified and hence you get an error. There are two solutions to your problem:
> 
> 1) add xmlns="" to the comment elements (What you have)
> 2) Change the value of elementFormDefault to "qualified"
> 
> To read more about namespaces see [1]

I do need to read more about namespaces...

> 
> Hope that helps,
> /Eddie

helps a lot!!!


> 
> [1] http://www.w3.org/TR/xmlschema-0/#NS
> 
> > Somehow, I think I just don't understand the right way to do things :-).
> >
> > Thanks for any help.
> >
> > -------------------------
> > A subset of our Schema is below.  It doesn't do what I want.  It fails
> > in the following way both with TIBCO's TurboXML and with SAX2Count from
> > xerces-c1_6_0-linux.
> >
> > 1) (above) The error in TurboXML is:
> >
> > Element "RotationSection": expected Rotation
> >
> > And with SAX2Count I get:
> >
> > Error at file
> > /home/mec/Projects/DetectorDescription/G3Convert_0_1_1/DDLSchema/DDLTestRotationInstance.xml,
> > line 8, char 20
> >   Message: Element 'comment' is not valid for content model:
> > '(comment*,Rotation*)'
> >
> > Which happen when comment elements come after Rotation elements inside a
> > RotationSection... (example below).
> >
> > 2) (above) The error in TurboXML is:
> >
> > Element "RotationSection": expected Rotation or comment (with no
> > namespaces)
> >
> > SAX2Count I get:
> >
> > Error at file
> > /home/mec/Projects/DetectorDescription/G3Convert_0_1_1/DDLSchema/DDLTestRotationInstance.xml,
> > line 6, char 12
> >   Message: Element 'comment' should be un-qualified
> >
> > =============== XML Schema =====================
> >
> > <?xml version = "1.0" encoding = "UTF-8"?>
> > <!--Generated by XML Authority. Conforms to w3c
> > http://www.w3.org/2001/XMLSchema-->
> > <xsd:schema xmlns = "http://www.cern.ch/cms/DDL"
> >          targetNamespace = "http://www.cern.ch/cms/DDL"
> >          xmlns:xsd = "http://www.w3.org/2001/XMLSchema"
> >          elementFormDefault = "unqualified"
> >          attributeFormDefault = "unqualified">
> >
> >         <xsd:element name = "DDDefinition" type = "DDDefinitionType"/>
> >         <xsd:complexType name = "DDDefinitionType">
> >                 <xsd:sequence>
> >                         <xsd:element ref = "Section" minOccurs = "0" maxOccurs =
> > "unbounded"/>
> >                 </xsd:sequence>
> >         </xsd:complexType>
> >
> >         <xsd:element name = "Section" type = "SectionType" abstract = "true"/>
> >         <xsd:element name = "RotationSection" type = "RotationSectionType"
> > substitutionGroup = "Section"/>
> >         <xsd:complexType name = "SectionType">
> >                 <xsd:sequence>
> >                         <xsd:element name = "comment" type = "xsd:string" minOccurs = "0"
> > maxOccurs = "unbounded"/>
> >                 </xsd:sequence>
> >                 <xsd:attributeGroup ref = "SectionAttributes"/>
> >         </xsd:complexType>
> >         <xsd:attributeGroup name = "SectionAttributes">
> >                 <xsd:attribute name = "label" use = "optional" type = "xsd:string"/>
> >         </xsd:attributeGroup>
> >
> >         <xsd:complexType name = "RotationSectionType">
> >                 <xsd:complexContent>
> >                         <xsd:extension base = "SectionType">
> >                                 <xsd:sequence>
> >                                         <xsd:element ref = "Rotation" minOccurs = "0" maxOccurs =
> > "unbounded"/>
> >                                 </xsd:sequence>
> >                         </xsd:extension>
> >                 </xsd:complexContent>
> >         </xsd:complexType>
> >
> >         <xsd:element name = "Rotation" type = "RotationType"/>
> >         <xsd:complexType name = "RotationType">
> >                 <xsd:attributeGroup ref = "RotationAttributes"/>
> >         </xsd:complexType>
> >         <xsd:attributeGroup name = "RotationAttributes">
> >                 <xsd:attribute name = "name" use = "required" type = "xsd:string"/>
> >                 <xsd:attribute name = "theta1" use = "required" type = "xsd:float"/>
> >                 <xsd:attribute name = "phi1" use = "required" type = "xsd:float"/>
> >                 <xsd:attribute name = "theta2" use = "required" type = "xsd:float"/>
> >                 <xsd:attribute name = "phi2" use = "required" type = "xsd:float"/>
> >                 <xsd:attribute name = "theta3" use = "required" type = "xsd:float"/>
> >                 <xsd:attribute name = "phi3" use = "required" type = "xsd:float"/>
> >                 <xsd:attribute name = "angleUnit" use = "optional" type =
> > "xsd:float"/>
> >         </xsd:attributeGroup>
> > </xsd:schema>
> >
> > ========================= Instance example ===========================
> >
> > <?xml version = "1.0" encoding = "UTF-8"?>
> > <DDDefinition xmlns = "http://www.cern.ch/cms/DDL" xmlns:xsi =
> > "http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation =
> > "http://www.cern.ch/cms/DDL
> > file:///home/mec/Projects/DetectorDescription/G3Convert_0_1_1/DDLSchema/DDLTestRotation.xsd">
> >         <RotationSection label = "blah">
> >                 <comment xmlns = ""/>
> >                 <Rotation name = "chfghfhf" theta1 = "0" phi1 = "0" theta2 = "0" phi2
> > = "0" theta3 = "0" phi3 = "0"/>
> >                 <comment xmlns = ""/>
> >                 <comment xmlns = ""/>
> >         </RotationSection>
> > </DDDefinition>
> >
> > --
> >
> > Michael E. Case
> > UC Davis
> > case@ucdhep.ucdavis.edu
> > (530) 754-7226

-- 

Michael E. Case
UC Davis
case@ucdhep.ucdavis.edu
(530) 754-7226
Received on Friday, 18 January 2002 16:10:18 GMT

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