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RE: About those "non-deterministic content model" errors

From: Fuchs, Matthew <matthew.fuchs@commerceone.com>
Date: Tue, 9 Jan 2001 13:30:07 -0800
Message-ID: <4C4A7BE77CE1D311A1D200508BA38C1202F35374@venus.commerceone.com>
To: "'Slein, Judith A'" <JSlein@crt.xerox.com>, "'www-xml-schema-comments@w3.org'" <www-xml-schema-comments@w3.org>
A cursory glance through section 3.10 leads me to a two part response:

1) I'm not sure the authors understand the XSDL extension mechanism.  In any
case, I'd love a more in-depth discussion than "this mechanism is not
allowed to be applied to any elements defined by JDF because  such new
element types can only be understood by the agent that made the extensions"
given the amount of work done to make sure that that statement is false.
That you use extension in your example is especially confusing.

2) The use of "any" is not the best way to get what you want, anyway.  One
possibility is the following:

<element name="PrivateExtension" type="xsd:AnyType"/>
<element name="ResourcePool" type="jdf:ResourcePool"/>
<complexType name="ResourcePool">
   <complexContent>
      <extension base="jdf:GenericContent">
         <choice minOccurs="0" maxOccurs="unbounded">
            <element ref="jdf:Resource"/>
            <!-- Extension resources are allowed.  _They_can
_now_be_JDF_Resources_ 
                 They can, in fact, be any declared type from any schema,
whether derived or not -->
            <element ref="PrivateExtension" minOccurs="0"/>
         </choice>
      </extension>
   </complexContent>
</complexType>

An optional PrivateExtension should appear wherever extensions are allowed,
per JDF.  This ensures, as they want, that "private extensions" can appear
in any of these places.  It is also clearly marked as a private extension -
and either refinement or substitution groups can be used to distinguish the
desired content without any concern for nondeterministic content models.  I
would consider this the best solution that doesn't allow you to extend the
base JDF types.  It solves their "issue" (no use of extensions for base JDF
types) while maintaining type safety.

If they're really dead set against extensions, then you can give them a
PrivateExtension type which explicitly allows <any> content.

Matthew

> -----Original Message-----
> From: Slein, Judith A [mailto:JSlein@crt.xerox.com]
> Sent: Tuesday, January 09, 2001 12:28 PM
> To: Fuchs, Matthew; Slein, Judith A; 'www-xml-schema-comments@w3.org'
> Subject: RE: About those "non-deterministic content model" errors
> 
> 
> The JDF specification is at http://www.job-definition-format.org.  The
> discussion of extensions is in section 3.10.  The notion 
> "private extension"
> is not defined.
> 
> Basically, the JDF spec discourages the use of derived types 
> for extensions.
> This leads to my assumption that it will use "any" at 
> extension points in
> its XML Schema.  But using "any" at these points just pushes 
> the task of
> enforcement of semantics into JDF-specific code -- the intent 
> is still that
> the elements that can appear at these points must be of the 
> "right sort".
> In the example, they must have the same structure as if they had been
> derived from the complexType jdf:Resource, even though 
> actually deriving
> them is discouraged.
> 
> Since you can get so much more powerful enforcement of 
> constraints by using
> derived types, we want to go ahead and do so (in our own 
> namespace).  But
> for now, the XML Schema spec is preventing us from doing so, since the
> schema processor then cannot determine whether it should use the
> jdf:Resource branch or the "any" branch in the choice to validate our
> extension element.  We want the jdf:Resource branch to be used.
> 
> Anyhow, I don't think this problem will be unique to JDF.  
> Just imagine any
> case where I am faced with an XML Schema written by somebody 
> else, which I
> want to extend.  It has in it the construct in the example.  Now I can
> define an element and its type from scratch, independent of 
> the definition
> of jdf:Resource.  In that case they will be validated using 
> the "any" branch
> of the choice.  But this is a much weaker form of validation 
> than I could
> get if there were a rule in XML Schema that in this sort of 
> case, a schema
> processor should validate using the more restrictive branch 
> if possibe, and
> only use the "any" branch as a last resort.  Then I could 
> derive a type from
> the jdf:Resource complexType, and create an element with
> substitutionGroup="jdf:Resource", and it would be validated 
> to be sure it is
> in fact of type jdf:Resource.
> 
> --Judy
> 
> -----Original Message-----
> From: Fuchs, Matthew [mailto:matthew.fuchs@commerceone.com]
> Sent: Tuesday, January 09, 2001 2:49 PM
> To: 'Slein, Judith A'; 'www-xml-schema-comments@w3.org'
> Subject: RE: About those "non-deterministic content model" errors
> 
> 
> I do not understand the "co-constraint" between your policy regarding
> extensions and your use of any.  What is a "private 
> extension".  Can you
> give a pointer to the JDF spec to explain these things?  I 
> can't tell if
> what you're trying to do is "reasonable" until I can 
> understand the goal.
> 
> Thanks,
> 
> Matthew Fuchs
> 
> > -----Original Message-----
> > From: Slein, Judith A [mailto:JSlein@crt.xerox.com]
> > Sent: Tuesday, January 09, 2001 8:34 AM
> > To: 'www-xml-schema-comments@w3.org'
> > Subject: FW: About those "non-deterministic content model" errors
> > 
> > 
> > When I sent this note to Henry Thompson, he suggested that I 
> > send a comment
> > to the XML Schema working group.  So here is the example I 
> > sent him, and his
> > response:
> > 
> > <HT>I think I understand the design goal and agree it's 
> > reasonable.  The
> > problem is not with XSV, but with the XML Schema spec. 
> itself.  Given
> > the example, the relevant element in the instance could be
> > accepted by either branch of the <choice>, and that's not allowed.
> > 
> > Please send this example to www-xml-schema-comments and 
> > prefix it with 
> > the observation that without a version of 'any' which 
> explicitly does 
> > _not_ validate anything which would cause a violation of the unique
> > attribution restriction you can't do what you (quite 
> reasonably) want
> > to do.</HT>
> > 
> > -----Original Message-----
> > From: Slein, Judith A 
> > Sent: Monday, January 08, 2001 9:47 AM
> > To: 'ht@cogsci.ed.ac.uk'
> > Subject: About those "non-deterministic content model" errors
> > 
> > 
> > These errors have been causing me no end of headaches, and it 
> > seems to me
> > XSV should be able to figure out what to do.
> > 
> > I'm in the situation of having to implement the JDF spec, 
> > which is being
> > developed by a printing industry consortium.  The JDF spec 
> > does not include
> > an XML Schema yet, but it seems relatively easy to figure out 
> > from their
> > models what the schema will look like, so I've taken a stab a 
> > writing one.
> > The spec forbids the use of derived types for extensions 
> > except in the case
> > of "private extensions".  So I'm assuming they will put "any" and
> > "anyAttribute" at all the extension points.  However, we 
> > would like to use
> > derived types in spite of their prohibition, and just say 
> that we are
> > defining private extensions.  So you get definitions like:
> > 
> > <element name="ResourcePool" type="jdf:ResourcePool"/>
> > <complexType name="ResourcePool">
> >    <complexContent>
> >       <extension base="jdf:GenericContent">
> >          <choice minOccurs="0" maxOccurs="unbounded">
> >             <element ref="jdf:Resource"/>
> > <!-- Extension resources are allowed.  They must have the 
> structure of
> >      JDF resources, but JDF doesn't allow the use of derived types
> >      to define them.  We will use derived types anyhow, but 
> > to be prepared
> >      for non-derived resources from 3rd parties . . . -->
> >             <any namespace="##other" processContents="lax"/>
> >          </choice>
> >       </extension>
> >    </complexContent>
> > </complexType>
> > 
> > Then we define in our namespace new types derived from 
> > Resource.  Using our
> > derived types in an instance document then causes the 
> > "non-deterministic
> > content model" schema error.  But since we declare the 
> > substitutionGroup of
> > our elements to be "jdf:Resource", it seems to me that a 
> > schema validator
> > should try to use the more restrictive validation path.  That 
> > is, it could
> > have a rule that says, if you can validate this without 
> > resorting to "any",
> > do so. Otherwise, use "any".
> > 
> > What do you think?
> > 
> > --Judy
> > 
> > 
> > 
> > -----Original Message-----
> > From: ht@cogsci.ed.ac.uk [mailto:ht@cogsci.ed.ac.uk]
> > Sent: Friday, January 05, 2001 4:51 PM
> > To: Slein, Judith A
> > Cc: 'xmlschema-dev@w3.org'
> > Subject: Re: False "undefined type" error from XSV
> > 
> > 
> > Can't reproduce with the current version, sorry.  Try upgrading to
> > XSV11.EXE, and try again.
> > 
> > Here are the error messages I get from the current version:
> > 
> > <schemaError char='55' line='371' phase='instance'
> > resource='file:///projects/lt
> > g/users/ht/xml/xmlschema/monk/slein/JDF.xsd'>non-deterministic
> >  content 
> > model for
> >  type ResourcePool: {Wildcard:
> > ##other}/{http://www.xerox.com/xmlschemas/DigiFin
> > ish}:BindingIntent</schemaError>
> > <schemaWarning char='31' line='99' phase='instance'
> > resource='file:///projects/l
> > tg/users/ht/xml/xmlschema/monk/slein/JDF.xsd'>restricting a 
> list with
> > facets not
> >  implemented yet</schemaWarning>
> > <schemaWarning char='31' line='99' phase='instance'
> > resource='file:///projects/l
> > tg/users/ht/xml/xmlschema/monk/slein/JDF.xsd'>restricting a 
> list with
> > facets not
> >  implemented yet</schemaWarning>
> > <schemaWarning char='31' line='99' phase='instance'
> > resource='file:///projects/l
> > tg/users/ht/xml/xmlschema/monk/slein/JDF.xsd'>restricting a 
> list with
> > facets not
> >  implemented yet</schemaWarning>
> > <schemaError char='63' line='532' phase='instance'
> > resource='file:///projects/lt
> > g/users/ht/xml/xmlschema/monk/slein/JDF.xsd'>non-deterministic
> >  content 
> > model for
> >  type ResourceLinkPool: {Wildcard:
> > ##other}/{http://www.xerox.com/xmlschemas/Dig
> > iFinish}:VerificationIntentLink</schemaError>
> > 
> > ht
> > -- 
> >   Henry S. Thompson, HCRC Language Technology Group, 
> > University of Edinburgh
> >           W3C Fellow 1999--2001, part-time member of W3C Team
> >      2 Buccleuch Place, Edinburgh EH8 9LW, SCOTLAND -- (44) 
> > 131 650-4440
> > 	    Fax: (44) 131 650-4587, e-mail: ht@cogsci.ed.ac.uk
> > 		     URL: http://www.ltg.ed.ac.uk/~ht/
> > 
> 
Received on Tuesday, 9 January 2001 16:30:37 GMT

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