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Re: Attributes ordering

From: <noah_mendelsohn@us.ibm.com>
Date: Thu, 22 Mar 2007 17:00:47 -0300
To: Nataraj Ramalingam <Nataraj.Ramalingam@aricent.com>
Cc: "Pete Cordell" <petexmldev@tech-know-ware.com>, xmlschema-dev@w3.org
Message-ID: <OFEE9DE1E9.DC5EA003-ON842572A6.006D8E6B-842572A6.006DF3C6@lotus.com>

This is trickier.  In schema 1.0, this schema is not legal.  It violates 
what's known as the unique particle attribution constraint.  Reason:  if 
you give it the instance <a/><c/>, you would have to look ahead to realize 
that the <c/> needs to be matched against the element reference and not 
the wildcard.  Schemas with such ambiguities or lookahead requirements are 
illegal in schema 1.0.  Still, I can translate what this schema is trying 
to say:

* the <a/> must come first
* a <c/> must come last
* any number of additional things including <a/>'s and </c>'s can come in 
the middle. 

My point is: order always matters in a sequence the fact that the <any> 
tends to accept lots of different things may appear to obscure that, but 
in the end, sequences are always ordered.

Noah Mendelsohn 
IBM Corporation
One Rogers Street
Cambridge, MA 02142

Nataraj Ramalingam <Nataraj.Ramalingam@aricent.com>
Sent by: xmlschema-dev-request@w3.org
03/22/2007 02:48 PM
        To:     "Pete Cordell" <petexmldev@tech-know-ware.com>
        cc:     xmlschema-dev@w3.org, (bcc: Noah Mendelsohn/Cambridge/IBM)
        Subject:        Re: Attributes ordering

Does the same hold good, if wildcard is used? 

In the same mentioned example, instead of b, let's assume that a wildcard 
<xs:complexType name="test">
               <xs:element name="a" type="xs:string"/>
                   <xs:any namespace="##other" processContents="lax" 
minOccurs="0" maxOccurs="unbounded"/>
               <xs:element name="c" type="xs:string"/>

<xs:element name="test" type="test"/> 

In this case, can there be instances of following possibilities, 
a,c, b, b          where b is an element of some other namespace. 

I see that in some of the IETF protocols, only whenever wildcard is used, 
the order of elements inside a sequence seems strange. It simply allows 
any possibilities, almost breaking the expected sequence behavior. 
COuld this be clarified? 

Kind Regards, 

"Pete Cordell" <petexmldev@tech-know-ware.com> 
Sent by: xmlschema-dev-request@w3.org 
03/22/2007 11:27 PM 

Nataraj Ramalingam/CHE/HSS@HSS 
Re: Attributes ordering

Original Message From: "Nataraj Ramalingam" <Nataraj.Ramalingam@...>

>. I have one more doubt w.r.t ordering of elements.
> consider the following example.
> =====================================================
> <xs:complexType name="test">
>        <xs:sequence>
>                <xs:element name="a" type="xs:string"/>
>                <xs:element name="b" type="xs:string" minOccurs="0"/>
>                <xs:element name="c" type="xs:string"/>
>        </xs:sequence>
> </xs:complexType>
> <xs:element name="test" type="test"/>
> =====================================================
> Eventhough we use a sequence type here, does this mandate the order of
> elements in the instance to be only a,b,c.
> Or, since "b" is optional ( minOccurs=0 ), can it (should it, by any 
> )come after "c" in the instance? for example, can the ordering be a,c,b?

As it's a sequence, if b is present, then it must appear between a and c 
(i.e. the same order as specified in the definition).  (so a, b, c or just 

a, c.)

The xs:all construct for the order to be changed, but there are currently 
numerous restrictions on that.


Pete Cordell
Tech-Know-Ware Ltd
for XML to C++ data binding visit

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Received on Thursday, 22 March 2007 20:01:31 UTC

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