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Re: Section 5 vs Schema

From: Jacek Kopecky <jacek@systinet.com>
Date: Tue, 29 Jan 2002 14:06:18 +0100 (CET)
To: <noah_mendelsohn@us.ibm.com>
cc: Martin Gudgin <marting@develop.com>, XML Protocol Discussion <xml-dist-app@w3.org>
Message-ID: <Pine.LNX.4.33.0201291402040.19721-100000@mail.idoox.com>
 Noah, just a minor point:

 The two examples below are not precisely equivalent:

    <greeting>Hello</greeting>
    <salutation>Hello</salutation>

    <greeting id="0">Hello</greeting>
    <salutation ref="0" />

 That's because in the latter, the values have some relation and 
if one changes, the other does as well, while in the former 
example the values are independent. I think you wanted to say 
that the latter example, while a valid SOAP Encoding graph, is 
not valid according to the schema provided.

 Overall, I agree with what you are saying.

 Best regards,

                   Jacek Kopecky

                   Senior Architect, Systinet (formerly Idoox)
                   http://www.systinet.com/



On Mon, 28 Jan 2002 noah_mendelsohn@us.ibm.com wrote:

 > Gudge: let me take a stab at the questions that I think you are really 
 > asking.  There are several uses the schemas in chapter 4, that should be 
 > distinguished:
 > 
 > Derivation of simple types
 > ==========================
 > 
 > Section 4.2 [1}, for example, illustrates the use of W3C XML Schema to 
 > declare a derived simple type.  As noted in [2], I think this may be 
 > appropriate insofar as the schema language is a normative W3C 
 > recommendation, and to clarify the possibility of using the derivation 
 > mechanism provided therein.  What I would suggest is the following 
 > additions to the specification:
 > 
 > * Make clear the validation of such types is optional, and that in the 
 > absence of validation we have a type whose name is known, but with 
 > indeterminate relation to any of the built-in types, and with any content 
 > accepted (simple, complex, mixed, etc. in W3C schema terms).  Contents is 
 > checked only when validation is performed.
 > 
 > * Also make clear that the use of other schema languages to declare types 
 > is acceptable, but that the soap specification mandates no validation for 
 > such languages either.
 > 
 > * Make clear that when validation wrt/ any schema language is to be 
 > performed, it is the responsibility of the communicating nodes to agree on 
 > the schema language to be used, the schemas to be used, the nature of the 
 > faults to be reflected if validation fails, etc.  I believe that such 
 > rules should apply equally to W3C schemas and to others.
 > 
 > Other Uses of Schemas in Chapter 4
 > ==================================
 > 
 > In section 4.2.1 [3], a schema is offered as a sample to describe the 
 > following instance fragment:
 > 
 >         Sample encoded instance fragment:
 >         <greeting>Hello</greeting>
 >         <salutation>Hello</salutation>
 > 
 >         Sample schema:
 >         <?xml version="1.0" ?>
 >         <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
 >            xmlns:enc="http://www.w3.org/2001/12/soap-encoding" >
 > 
 >           <xs:import namespace="http://www.w3.org/2001/12/soap-encoding" 
 > />
 > 
 >           <xs:element name="greeting" type="enc:string" />
 >           <xs:element name="salutation" type="enc:string" />
 > 
 >         </xs:schema>
 > 
 > I agree that this is misleading and inappropriate, and I suspect that is 
 > the true essence of your concern.  The schema is basically modeling an XML 
 > tree, whereas the encoding conveys a directed label graph.  Using one to 
 > model the other is just inappropriate (and this by the way is one of my 
 > concerns about the current design of WSDL).  Indeed, it obscures the whole 
 > point of this section, which is that from the point of view of the 
 > encoding (but not the schema!), the fragment above is equivalent to:
 > 
 >         <greeting id="String-0">Hello</greeting>
 >         <salutation href="#String-0"/>
 > 
 > Furthermore, as you point out, one of the main reasons to have the 
 > encoding at all is that the data becomes substantially self describing. 
 > While creating a schema for such data is not strictly wrong, I agree that 
 > it does not belong in our specification.
 > 
 > Bottom line: I think I would restrict examples using W3C XML schema to 
 > cases like the one in section 4.2 as discussed above.
 > 
 > Thank you very much.
 > 
 > [1] http://www.w3.org/TR/soap12-part2/#simpletypes
 > [2] http://lists.w3.org/Archives/Public/xml-dist-app/2002Jan/0378.html
 > [3] http://www.w3.org/TR/soap12-part2/#stringtypes
 > 
 > ------------------------------------------------------------------
 > Noah Mendelsohn                              Voice: 1-617-693-4036
 > IBM Corporation                                Fax: 1-617-693-8676
 > One Rogers Street
 > Cambridge, MA 02142
 > ------------------------------------------------------------------
 > 
 > 
 > 
Received on Tuesday, 29 January 2002 08:06:21 GMT

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