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RE: Importing schemata into WSDL

From: Jacek Kopecky <jacek@systinet.com>
Date: 15 Oct 2002 09:58:55 +0200
To: Martin Gudgin <mgudgin@microsoft.com>
Message-Id: <1034669050.5046.20.camel@krava>

I like that. 8-)

Is this like saying (however softly and quietly) that we don't buy point
1 below about XML Schema? 8-) You're free to ignore this cheeky
question. 8-)


                   Jacek Kopecky

                   Senior Architect, Systinet Corporation
                   http://www.systinet.com/


On Tue, 2002-10-15 at 05:56, Martin Gudgin wrote:
> 
> I've been thinking a bit more about this. How about
> 
> <wsdl:types>
>   <xs:import namespace='http://example.org/foo' />
>   <xs:import namespace='http://example.org/bar' />
> 
>   <xs:schema targetNamespace='http://example.org/baz' >
>     <xs:import namespace='http://example.org/quux' />
>   </xs:schema>
> </wsdl:types>
> 
> and say that schema components in foo, bar and baz are visible to WSDL
> components but schema components in quux are only visible to the inline
> schema. Schema components in foo and bar are NOT visible to the inline
> schema.
> 
> Gudge
> 
> > -----Original Message-----
> > From: Don Mullen [mailto:donmullen@tibco.com] 
> > Sent: 11 October 2002 19:54
> > To: Martin Gudgin
> > Cc: Jacek Kopecky; WS Description WG
> > Subject: RE: Importing schemata into WSDL
> > 
> > 
> > 
> > Martin:
> > 
> > I understand how you can argue this position.  In XML Schema 
> > spec (part 1), section 4.2.3, we have:
> > 
> > "The *schema components* (that is {type definitions}, 
> > {attribute declarations}, {element declarations}, {attribute 
> > group definitions}, {model group definitions}, {notation 
> > declarations}) of a schema corresponding to a <schema> 
> > element information item with one or more <import> element 
> > information items must include not only definitions or 
> > declarations corresponding to the appropriate members of its 
> > [children], but also, for each of those <import> element 
> > information items for which clause 2 above is satisfied, a 
> > set of *schema components* identical to all the *schema 
> > components* of I." 
> > 
> > So all the schema components that are <import>ed are 
> > available to reference by the importing schema.  In addition, 
> > an XML instance document that uses the a.xsd schema must be 
> > able to access components within all three namespaces.
> > 
> > <aNS:x xsi:schemaLocation"a.xsd" xmlns:aNS="fooA" 
> > xmlns:bNS="fooB" xmls:cNS="fooC">  <bNS:y>
> >   <cNS:z/>
> >  </bNS:y>
> > </aNS:x>
> > 
> > However, as you indicated below, a.xsd can't reference c.xsd, 
> > even though b.xsd <import>ed c.xsd.  So by that argument, I 
> > don't see why bar.wsdl should be able to reference anything 
> > in b.xsd if a.xsd is included inline within <types>.  I would 
> > think it should mirror XML Schema, and require a separate 
> > <import> of b.xsd in order to reference those components 
> > directly. I guess I see a difference between reference the 
> > component definitions (as referenced in schemas or wsdls), 
> > and actual use of the components in an instance doc.
> > 
> > Don
> > 
> > > -----Original Message-----
> > > From: Martin Gudgin [mailto:mgudgin@microsoft.com]
> > > Sent: Friday, October 11, 2002 8:44 PM
> > > To: Jacek Kopecky; WS Description WG
> > > Subject: RE: Importing schemata into WSDL
> > > 
> > > Jacek,
> > > 
> > > I'm afraid I disagree with your analysis of how schema 
> > import works. 
> > > Here's why.
> > > 
> > > Taking your example:
> > > 
> > > Given three schema documents a.xsd, b.xsd and c.xsd with
> > > three separate
> > > target namespaces, where a.xsd imports b.xsd imports c.xsd it is my
> > > understanding that the following statements are true:
> > > 
> > > 1.  The resulting schema contains components from all three 
> > namespaces
> > > 
> > > 2.  Components in namespace a can only reference components
> > > in namespace
> > > a and/or namespace b
> > > 
> > > 3.  Components in namespace b can only reference components
> > > in namespace
> > > b and/or namespace c
> > > 
> > > 4.  Components in namespace c can only reference other 
> > components in 
> > > namespace c.
> > > 
> > > Note that the reason components in namespace a cannot reference 
> > > components in namespace c ( point 2 ) is because a.xsd does 
> > not have 
> > > an import for namespace c and the schema spec is very clear that
> > > you cannot
> > > reference things in a namespace you have not imported ( same 
> > > applies to
> > > points 3 and 4 ).
> > > 
> > > However, the critical point from the POV of the component
> > > model for WSDL
> > > is point 1. All we need to say is that for any <xs:schema> 
> > element in
> > > <wsdl:types> ALL the schema components directly defined in the
> > > <xs:schema> and those directly imported are visible to the 
> > rest of the
> > > WSDL components and can be referenced. Strictly speaking we 
> > could also
> > > say that you can reference components in other namespaces the are
> > > imported at a deeper level, because those components ARE 
> > present, but
> > > there would be no way of knowing about them in the WSDL 
> > > itself without a
> > > priori knowledge of the schemas you were directly importing.
> > > 
> > > Gudge
> > > 
> > > > -----Original Message-----
> > > > From: Jacek Kopecky [mailto:jacek@systinet.com]
> > > > Sent: 11 October 2002 18:16
> > > > To: WS Description WG
> > > > Subject: Importing schemata into WSDL
> > > > 
> > > > 
> > > > 
> > > > Hi all, 8-)
> > > > 
> > > > in WSDL 1.1 the import statement allowed importing schema
> > > > documents. In WSDL 1.2 we are apprarently moving in the 
> > > > direction of disallowing this, but we acknowledge it must be 
> > > > possible to import an external schema into a WSDL definitions 
> > > > document somehow.
> > > > 
> > > > What I've heard from Gudge is that it is possible to import a
> > > > schema at http://example.org/schema.xs (with the same target 
> > > > namespace) using
> > > > 
> > > > <wsdl:types>
> > > >   <xs:schema>
> > > >     <xs:import namespace="http://example.org/schema.xs"
> > > >                location="http://example.org/schema.xs"/>
> > > >   </xs:schema>
> > > > </wsdl:types>
> > > > 
> > > > I have a problem with this because IMHO this violates XML
> > > > Schema import semantics. Let me explain:
> > > > 
> > > > Let's assume I have three schemas, a.xs, b.xs and c.xs, with
> > > > different target namespaces; where a.xs only imports b.xs and 
> > > > b.xs imports c.xs. On the component level; a.xs then contains 
> > > > all the type and element definitions from a.xs and all the 
> > > > type and element definitions from b.xs are accessible in a.xs. 
> > > > 
> > > > Note that no definitions from c.xs are visible in a.xs - this
> > > > is logical because the fact that b.xs imports c.xs is just an 
> > > > implementation detail of b.xs and should not be propagated 
> > > > outside of b.xs. In other words, a.xs must not be affected by 
> > > > a change to b.xs that only removes the import and redefines 
> > > > those definitions (still in b.xs) that used definitions from c.xs.
> > > > 
> > > > What I think this means is that an xs:schema element
> > > > (together with any
> > > > contents) is a syntactic representation of the set of type 
> > > > and element definitions contained within.
> > > > 
> > > > I think it's apparent from the paragraph above that WSDL
> > > > should not know about imports in wsdl:types/xs:schema. I.e. a 
> > > > schema cannot be imported into a WSDL definitions document by 
> > > > importing it in a contained schema.
> > > > 
> > > > I think that we'll have to reallow our import statement to
> > > > import schemas (which should be doable in a safe way, I 
> > > > believe) or we should introduce a typesImport statement that 
> > > > would serve to import external schemata, as the types 
> > > > statement serves to provide (import) internal schemata.
> > > > 
> > > > Hope it makes sense,
> > > > 
> > > >                    Jacek Kopecky
> > > > 
> > > >                    Senior Architect, Systinet Corporation
> > > >                    http://www.systinet.com/
> > > > 
> > > > 
> > > > 
> > > > 
> > > 
> > > 
> > 
Received on Tuesday, 15 October 2002 04:04:32 GMT

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