RE: On Schemas, Namespaces and Syntax vs. Semantics (long but worth it) :)

["Dare Obasanjo" <dareo@microsoft.com>]

I am aware that your original discussion involved W3C XML Schema and WSDL. My point is that the way you plan to ise XSD is the wrong solution to the kind of problem you originally described. 
 
As for your comments about schemas. 
 
> 2. XML Schema does not know versions, they know derivations. 
>If you want to extend a Schema, create a new one, import or reference the old one and restrict or extend the existing types.

Actually you can also use xs:redefine which allows one to extend the types defined in a schema in a pervasive manner without resorting to changing the targetNamespace of the schema. 

>3. (b) XML Schema knows extensibility, however. 
> Carefully consider providing extensibility points in your messages through the use of xsd:any.

wildcards are just one of many ways to provide extensibility in schemas and they have their advantages and disadvantages. I've written about them in the past[0]. I actually can't wait until authors of schema validators catch on to allowing users to perform lax validation at will since this allows for open content schemas similar to what we had in XML-Data Reduced (XDR).  

>And these are very much in line with what you are saying and I am certain that I didn't contradict myself in the later snippet that you  were initially referring to.

Your original article describes a couple of dos and don'ts for using W3C XML Schema and WSDL. Not being a web services person I have no opinion on the guidelines you provide nor can I judge their veracity. 

However your weblog describes a specific customer scenario involving XML which I do know. And based on my knowledge of XML, I disagreed with your conclusion which implied that namespaces and schemas should be used to convey application semantics. 

[0] http://www.xml.com/pub/a/2002/07/03/schema_design.html


	-----Original Message----- 
	From: Clemens Vasters [mailto:clemensv@newtelligence.com] 
	Sent: Sun 7/28/2002 3:03 AM 
	To: Dare Obasanjo; xml-dev@lists.xml.org 
	Cc: 
	Subject: RE: On Schemas, Namespaces and Syntax vs. Semantics (long but worth it) :)
	
	


	"The fact that your attempts at foolproofing involve W3C XML Schema
	already assures me they aren't."
	
	The discussion is about XML Schema and the use of XML. Nothing more,
	nothing less. I appreciate your input and thoughts on this, but I have
	the impression that you are coming from an angle that this discussion
	was never meant to cover or adress.
	
	Besides... in my initial document [1] there are the following "rules":
	
	2. XML Schema does not know versions, they know derivations. If you want
	to extend a Schema, create a new one, import or reference the old one
	and restrict or extend the existing types.
	
	3. (b) XML Schema knows extensibility, however. Carefully consider
	providing extensibility points in your messages through the use of
	xsd:any.
	
	And these are very much in line with what you are saying and I am
	certain that I didn't contradict myself in the later snippet that you
	were initially referring to.
	
	Best Regards,
	Clemens
	
	---------------------
	Clemens F. Vasters
	CTO, newtelligence AG
	Gilleshütte 99
	D-41352 Korschenbroich
	Germany
	
	MSDN Regional Director
	clemensv@newtelligence.com
	v-clevas@microsoft.com
	
	
	[1]
	http://radio.weblogs.com/0108971/stories/2002/07/23/stayingSaneInAnXmlWe
	bServicesWorld.html