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

From: Amelia A. Lewis <alewis@tibco.com>
Date: Fri, 17 Oct 2003 14:17:46 -0400
To: Lawrence Mandel <lmandel@ca.ibm.com>
Cc: 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: <20031017141746.7dddd6bd.alewis@tibco.com>

*sigh*

@schemaLocation is a *hint*.

All of the examples are valid.  All of the schemaLocation attributes
specified may be ignored.

It would be far better for the WSDL specification to *recommend* that
when embedded schemas import other embedded schemas, the schemaLocation
attribute SHOULD be omitted.

Schema processors are supposed to be called in some sort of context. 
Specifically, since the schemaLocation attribute is a hint, they are
often expected to be called in the context of some object or API that
provides catalog-like facilities.

Modifying the WSDL spec to say "don't use cataloging", even if the
suggestion is only implicit, is not, in my opinion, wise.  Suggesting
that best practice would omit schemaLocation, and that the schema
processor should be called in a cataloging context that permits
resolution of the embedded schemas as they are load, seems fine, but
this is advisory language, not normative.

Amy!
On Fri, 17 Oct 2003 14:08:20 -0400
Lawrence Mandel <lmandel@ca.ibm.com> wrote:

> 
> 
> 
> 
> 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     
>                                            
>                                                                    Su
>                                                                    bj
>                                                                    ect
>                                                                    
>                                        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
> 
> 
> 


-- 
Amelia A. Lewis
Architect, TIBCO/Extensibility, Inc.
alewis@tibco.com
Received on Friday, 17 October 2003 14:18:28 GMT

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