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RE: Section 5 vs Schema

From: Don Box <dbox@microsoft.com>
Date: Thu, 31 Jan 2002 12:52:09 -0800
Message-ID: <CFC4F26947496E4092489B24256149580414BF96@svc-msg-02.northamerica.corp.microsoft.com>
To: <noah_mendelsohn@us.ibm.com>, <jacek@systinet.com>
Cc: "Martin Gudgin" <marting@develop.com>, "XML Protocol Discussion" <xml-dist-app@w3.org>
Although, I believe that one could express all section 5-isms (typed
references, arrays) using idioms currently supported in schema + a
handful of NS-qualified attributes.

DB
 

> -----Original Message-----
> From: noah_mendelsohn@us.ibm.com [mailto:noah_mendelsohn@us.ibm.com]
> Sent: Wednesday, January 30, 2002 12:17 PM
> To: jacek@systinet.com
> Cc: Martin Gudgin; XML Protocol Discussion
> Subject: Re: Section 5 vs Schema
> 
> Yes, you're right, my mistake, I oversimplified the explanation of the
> examples.  I think we agree on the key point, which is that XML Schema
is
> not an appropriate description language for the directed graphs used
by
> the encodings.  It would be easy to construct two examples that were
very
> different from a schema point of view, and identical per the graph
model.
> 
> ------------------------------------------------------------------
> Noah Mendelsohn                              Voice: 1-617-693-4036
> IBM Corporation                                Fax: 1-617-693-8676
> One Rogers Street
> Cambridge, MA 02142
> ------------------------------------------------------------------
> 
> 
> 
> 
> 
> 
> 
> Jacek Kopecky <jacek@systinet.com>
> 01/29/2002 08:06 AM
> 
> 
>         To:     Noah Mendelsohn/Cambridge/IBM@Lotus
>         cc:     Martin Gudgin <marting@develop.com>, XML Protocol
> Discussion
> <xml-dist-app@w3.org>
>         Subject:        Re: Section 5 vs Schema
> 
> 
>  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 Thursday, 31 January 2002 15:52:43 GMT

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