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RE: ISSUE-20: Extension of collections

From: <paul.downey@bt.com>
Date: Wed, 22 Feb 2006 09:12:20 -0000
Message-ID: <2A7793353757DB4392DF4DFBBC9522550276F378@I2KM11-UKBR.domain1.systemhost.net>
To: <petexmldev@tech-know-ware.com>, <edday@obj-sys.com>, <public-xsd-databinding@w3.org>

Pete, Ed

Thanks for the comments!

I'm personally not comfortable with this pattern, given it's:

a) as you say, not 'intuitive'

b) has a restriction on how the 2nd, 3rd etc evolutions 
   may be made represented (i'm guessing you'd end up
   with a staircase of nested <extension> elements.

However I'm keen to say 'something' for versioning!

I understand that at least two binding tools do make 
use of it when generating Schema from code, including at 
least one major tool developed by Microsoft. 

//I wondered if anyone else had personal experiences of 
such extension patterns with toolkits?//

However I also have personal experience with a tool from a well
known J2EE vendor who's service generator tool rejects the whole
WSDL at the first sign of an xs:any or xs:anyType inside a Schema! 

My current inclination is to avoid Recommending patterns which
use xs:any or xs:anyType in our Basic specification, and move
this subject to the Advanced patterns document.

This would be a blow to my personal aims in promoting patterns
for versioning and evolving messages, but probably be a better
statement in the art of the possible with current databinding tools.

Paul

-----Original Message-----
From: public-xsd-databinding-request@w3.org on behalf of Pete Cordell
Sent: Wed 2/22/2006 7:57 AM
To: Ed Day; Databinding WG
Subject: Re: ISSUE-20: Extension of collections
 

Hi Ed,

As I understand it, you are right.  The versioned type would become 
(including documentation about the versioning):

<xs:complexType name="CustomerType">
  <xs:sequence>
    <xs:element name="firstName" type="xs:string" />
    <xs:element name="lastName" type="xs:string" />
    <xs:element name="extension">
        <xs:complexType>
            <xs:annotation><xs:documentation>
                These members were added in version 2
            </xs:documentation></xs:annotation>
            <xs:sequence>
                <xs:element name="MyV2Element" type="xs:string"/>
                <xs:element name="extension" 
type="tns:CustomerExtensionType"
                                             minOccurs="0" />
            </xs:sequence>
        </xs:complexType>
    </xs:element>
  </xs:sequence>
  <xs:anyAttribute/>
</xs:complexType>

<xs:complexType name="CustomerExtensionType">
  <xs:sequence>
    <xs:any processContents="lax" minOccurs="0" maxOccurs="unbounded"
          namespace="##targetNamespace"/>
    </xs:sequence>
</xs:complexType>


Pete.
----- Original Message ----- 
From: "Ed Day" <edday@obj-sys.com>
To: "Databinding WG" <public-xsd-databinding@w3.org>
Sent: Tuesday, February 21, 2006 7:18 PM
Subject: Re: ISSUE-20: Extension of collections


>
> The problem with this approach is that it requires the user to embed the
> <extension> element within the instance being extended.  This is not what
> happens in the real world.  What happens is additional elements just show
> up.
>
> Also, what happens if the schema is extended a 2nd time?  Do you have an
> extension in an extension?  Or maybe the "extension" element should have
> some kind of version number on the end to track when an extension happened
> (<extension1>, <extension2>, etc.)?
>
> Regards,
>
> Ed Day
> Objective Systems, Inc.
> http://www.obj-sys.com
>
>
> ----- Original Message -----
> From: "Databinding Issue Tracker" <dean+cgi@w3.org>
> To: <public-xsd-databinding@w3.org>
> Sent: Tuesday, February 21, 2006 9:05 AM
> Subject: ISSUE-20: Extension of collections
>
>
>>
>>
>> ISSUE-20: Extension of collections
>>
>> http://www.w3.org/2005/06/tracker/databinding/issues/20
>>
>> Raised by: Paul Downey
>> On product: Basic
>>
>> The input document offers the following pattern for a collection
>> which is open to extension, thereby being useful when evolving
>> or extending a schema during versioning:
>>
>> """
>> <xs:complexType name="CustomerType">
>>   <xs:sequence>
>>     <xs:element name="firstName" type="xs:string" />
>>     <xs:element name="lastName" type="xs:string" />
>>     <xs:element name="extension" type="tns:CustomerExtensionType"
> minOccurs="0" />
>>   </xs:sequence>
>>   <xs:anyAttribute/>
>> </xs:complexType>
>>
>> <xs:complexType name="CustomerExtensionType">
>>   <xs:sequence>
>>     <xs:any processContents="lax" minOccurs="0" maxOccurs="unbounded"
>>           namespace="##targetNamespace"/>
>>     </xs:sequence>
>> </xs:complexType>
>>
>> """
>>
>> How well is this pattern supported by tools - does it belong in
>> the Basic patterns document?
>>
>> Are there authoring issues with this pattern we should warn about?
>>
>>
--
=============================================
Pete Cordell
Tech-Know-Ware Ltd
                         for XML to C++ data binding visit
                         http://www.tech-know-ware.com/lmx
                         (or http://www.xml2cpp.com)
=============================================
Received on Wednesday, 22 February 2006 09:14:52 GMT

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