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Re: Can one inline schema import definitions from a second inline schema?

From: Lawrence Mandel <lmandel@ca.ibm.com>
Date: Fri, 17 Oct 2003 14:08:20 -0400
To: "Amelia A. Lewis" <alewis@tibco.com>
Cc: Arthur Ryman <ryman@ca.ibm.com>, mgudgin@microsoft.com, paul.downey@bt.com, sanjiva@watson.ibm.com, www-ws-desc@w3.org, www-ws-desc-request@w3.org
Message-ID: <OFDCF86DF3.908FDBD7-ON85256DC2.0061FB7D-85256DC2.0063A4AA@ca.ibm.com>





I agree that using the schema language as intended is the best option.
However, the xs:import element was not designed with the idea of importing
a schema that is located in the same physical file as the schema that is
importing it. Existing schema processors do not know how to resolve inline
schemas by default and will have to be configured to do so. Not clarifying
the correct way to import an inline schema will result in different takes
on how to import an inline schema. This is a potential interoperability
problem that can be addressed at the WSDL specification level (rather then
leaving this for the WS-I Basic Profile). If this is not clarified, what
will it mean if someone has an import statement such as

<xs:import namespace="http://mynamespace" schemaLocation="mywsdl.wsdl"/>

Will that resolve http://mynamespace to another inline schema? Will the
following be valid?

<xs:import namespace="http://mynamespace"
schemaLocation="http://mynamespace"/>

Or is the correct way

<xs:import namespace="http://mynamespace"/>

I tend to think that not including a schemaLocation is the correct way but
there is currently nothing that will prevent others from using one of the
other two import statements.  Because WSDL is using XML Schema in a way
that it was not intended to be used the WSDL specification should make
clarifications to XML Schema where needed.

Alternatively, if the goal is to use XML Schema as it was designed, inline
schemas should not be allowed at all and all schemas should be defined in
external documents and imported into WSDL documents. This approach will
maintain the independence and integrity of XML Schema and reduce the amount
of clarifications the WSDL specification needs to make as a result of using
XML Schema internally in WSDL documents.

Comments?

Lawrence Mandel

Software Developer
WebSphere Studio Application Developer - XML Tools
Phone: 905 - 413 - 3814   Fax: 905 - 413 - 4920
lmandel@ca.ibm.com


                                                                           
             "Amelia A. Lewis"                                             
             <alewis@tibco.com                                             
             >                                                          To 
                                       paul.downey@bt.com                  
             10/17/2003 12:03                                           cc 
             PM                        mgudgin@microsoft.com,              
                                       sanjiva@watson.ibm.com, Arthur      
                                       Ryman/Toronto/IBM@IBMCA, Lawrence   
                                       Mandel/Toronto/IBM@IBMCA,           
                                       www-ws-desc@w3.org,                 
                                       www-ws-desc-request@w3.org          
                                                                   Subject 
                                       Re: Can one inline schema import    
                                       definitions from a second inline    
                                       schema?                             
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           




Do we need to do so?

The current language of the specification seems fairly straightforward.
We permit, as immediate children of types, when W3C XML Schema is used
(and it is the only schema language required to be supported by all WSDL
processors), both xs:schema and xs:import.  We *do not* constrain the
semantics of these child elements, except to change @targetNamespace to
REQUIRED (for embedded and imported schemata both).

We should not, in my opinion, overconstrain W3C XML Schema.  We have
already forbidden the use of chameleon schemata, which removes an
enormous burden on processors; support for that [mis?]feature would have
placed an unacceptable burden on the WSDL processor, since we would have
had to define the semantics of chameleon schemata in a context never
anticipated (the idea that a WSDL targetNamespace could apply to an
imported/embedded schema makes for all sorts of really interesting and
sometimes quite surprising interactions).

In so far as is possible, we should *not* change semantics of W3C XML
Schema, in my opinion.  The value of requiring it as a supported schema
language lies in the re-use of existing schema processors.  If we begin
to place further constraints upon it, it stops being the language
supported by existing processors, and requires a whole new generation of
processors customized for schema-in-WSDL-context.

The idea behind embedding and importing schema, as I understand it, is
to rule that whole complex area *out of scope* for the WSD WG.  Writing
a schema language is *hard*, we need to reuse, not reinvent, and not
revise.  This allows us to focus on what we [should?] do best.

Amy!
On Fri, 17 Oct 2003 16:39:32 +0100
paul.downey@bt.com wrote:

>
> isn't this an issue about how multiple inline schemas reference each
> other in a   single WSDL document ?
>
> AIUI it's just a matter of formally stating what appears to be a
> common practice.
>
> Paul
>
> -----Original Message-----
> From: Martin Gudgin [mailto:mgudgin@microsoft.com]
> Sent: 17 October 2003 16:36
> To: Downey,PS,Paul,XSJ67A C; sanjiva@watson.ibm.com; ryman@ca.ibm.com
> Cc: lmandel@ca.ibm.com; www-ws-desc@w3.org; www-ws-desc-request@w3.org
> Subject: RE: Can one inline schema import definitions from a second
> inline schema?
>
>
> Given that xs:import is defined by XML Schema and NOT WSDL, I don't
> see how WSDL can really constrain it in any way.
>
> Gudge
>
> > -----Original Message-----
> > From: paul.downey@bt.com [mailto:paul.downey@bt.com]
> > Sent: 17 October 2003 16:35
> > To: sanjiva@watson.ibm.com; Martin Gudgin; ryman@ca.ibm.com
> > Cc: lmandel@ca.ibm.com; www-ws-desc@w3.org;
> > www-ws-desc-request@w3.org Subject: RE: Can one inline schema import
> > definitions from a second inline schema?
> >
> > i don't think the BP doesn't preclude more than 1 schema
> > within the types section - though i couldn't see anything
> > about referencing between inline schemas.
> >
> > FWIW, quite a few existing kits (including .NET) will
> > generate WSDL 1.1 with multiple inline schemas which
> > reference each other using <import namespace="blah"> - with a
> > missing schemaLocation ..
> >
> > maybe the anonymous schemaLocation should be
> > supported/precluded explicitly in WSDL 1.2 ?
> >
> >
> > --
> > Paul Sumner Downey
> > Web Services Integration
> > BT Exact
> >
> >
> >
> >
> > -----Original Message-----
> > From: Sanjiva Weerawarana [mailto:sanjiva@watson.ibm.com]
> > Sent: 17 October 2003 16:02
> > To: Martin Gudgin; Arthur Ryman
> > Cc: Lawrence Mandel; www-ws-desc@w3.org; www-ws-desc-request@w3.org
> > Subject: Re: Can one inline schema import definitions from a second
> > inline schema?
> >
> >
> >
> > Didn't we discuss this a while back and say only *1* schema within
> > <types>?? Or maybe that WSI BP that does that?
> >
> > Sanjiva.
> >
> > ----- Original Message -----
> > From: "Arthur Ryman" <ryman@ca.ibm.com>
> > To: "Martin Gudgin" <mgudgin@microsoft.com>
> > Cc: "Lawrence Mandel" <lmandel@ca.ibm.com>; <www-ws-desc@w3.org>;
> > <www-ws-desc-request@w3.org>
> > Sent: Friday, October 17, 2003 7:56 PM
> > Subject: RE: Can one inline schema import definitions from a
> > second inline
> > schema?
> >
> >
> > > Gudge,
> > >
> > > I agree to some extent, but AFAIK, WSDL is the only application
> > > that inlines <schema>. I think the XSD spec assumes you have a
> > single <schema>
> > > per document, i.e. <schema> is the root element. So
> > processing not one,
> > > but two or more inline schemas is a bit of a shock for your
> > typical XSD
> > > processor. So probably the "reasonable" behavior you describe is
> > > undefined.
> > >
> > > I think it would promote interoperability if the WSDL 1.2
> > was clear on
> > > this point, one way or the other. From your response, I
> > assume you would
> > > support the use of more than one inline <schema> in the
> > <types> element.
> > >
> > > Arthur Ryman
> > >
> > >
> > >
> > >
> > > "Martin Gudgin" <mgudgin@microsoft.com>
> > > Sent by: www-ws-desc-request@w3.org
> > > 10/17/2003 06:17 AM
> > >
> > >
> > >         To:     Lawrence Mandel/Toronto/IBM@IBMCA,
> > <www-ws-desc@w3.org>
> > >         cc:
> > >         Subject:        RE: Can one inline schema import
> > definitions from
> > a second inline schema?
> > >
> > >
> > >
> > >
> > > To be frank, I think this has very little to do with WSDL. It is
> > > perfectly coherent for a schema processor, on encountering
> > <xsd:import
> > > namespace='http://namespace1' /> to say to itself, ah, I
> > have a schema
> > > for that namespace, I'll use that here. Likewise, when it
> > > encounters<xsd:import namespace='http://namespace2' /> it would
> > > say,
> > ah, not seen
> > > that namespace yet, I'll wait and see what happens.
> > >
> > > Gudge
> > >
> > > > -----Original Message-----
> > > > From: www-ws-desc-request@w3.org
> > > > [mailto:www-ws-desc-request@w3.org] On Behalf Of Lawrence Mandel
> > > > Sent: 16 October 2003 23:19
> > > > To: www-ws-desc@w3.org
> > > > Subject: Can one inline schema import definitions from a
> > > > second inline schema?
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > > Hello,
> > > >
> > > > We have customers that do the following in WSDL 1.1:
> > > >
> > > > <types>
> > > >  <schema targetNamespace="http://namespace1" xmlns=
> > > > "http://www.w3.org/2001/XMLSchema"
> > > > xmlns:two="http://namespace2">
> > > >    <import namespace="http://namespace2"/>
> > > >    <complexType name="myComplexType">
> > > >     <sequence>
> > > >      <element name="myElement" type="two:B"/>
> > > >     </sequence>
> > > >    </complexType>
> > > >    <complexType name="A">
> > > >     <sequence>
> > > >      <element name="elementA" type="xsd:string"/>
> > > >     </sequence>
> > > >    </complexType>
> > > >   </schema>
> > > >   <schema targetNamespace="http://namespace2" xmlns=
> > > > "http://www.w3.org/2001/XMLSchema"
> > > > xmlns:one="http://namespace1">
> > > >    <import namespace="http://namespace1"/>
> > > >    <complexType name="myComplexType">
> > > >     <sequence>
> > > >      <element name="myElement" type="one:A"/>
> > > >     </sequence>
> > > >    </complexType>
> > > >    <complexType name="B">
> > > >     <sequence>
> > > >      <element name="elementB" type="xsd:string"/>
> > > >     </sequence>
> > > >    </complexType>
> > > >   </schema>
> > > > </types>
> > > >
> > > > The customers say that this is not explicitly forbidden by
> > > > the WSDL 1.1 specification and I can't find anything that
> > > > forbids this in the WSDL 1.1 specification.  However, there
> > > > is nothing in the WSDL 1.1 specification that states how to
> > > > import a schema defined in the same types section but with a
> > > > different namespace.
> > > >
> > > > Is this allowed according to the WSDL 1.2 specification?  If
> > > > so, what is the correct way to import one inline schema
> > into another?
> > > >
> > > > Thanks,
> > > >
> > > > Lawrence Mandel
> > > >
> > > > Software Developer
> > > > WebSphere Studio Application Developer - XML Tools
> > > > Phone: 905 - 413 - 3814   Fax: 905 - 413 - 4920
> > > > lmandel@ca.ibm.com
> > > >
> > > >
> > > >
> > >
> > >
> > >
> > >
> >
> >
> >
>
>


--
Amelia A. Lewis
Architect, TIBCO/Extensibility, Inc.
alewis@tibco.com
Received on Friday, 17 October 2003 14:08:29 GMT

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