Re: [xml-dev] Perplexing Invalid Schema

[Timothy Cook <timothywayne.cook@gmail.com>]

Thanks Michael.  Apologies that I did not notice that it wasn't
initially sent to the list.  Just my habit of being sure a thread on
the list is always there.

Back to the subject.  I understand your explanation.  However, I
cannot conclude that there is a technical reason for not allowing
this.  Derivation allows for both extension and restriction.  In this
case it seems to me that first derivation should be checked and then
test for content of the derived type.

For example:
Is 'Any' an ancestor of  'DT1-1'? - Yes.
Are each of the extensions and restrictions specified in the ancestry
tree satisfied in DT1-1? - Yes.

Is this reasonable?  If anyone can speak to why the specs read the way
they do; I would appreciate it.  My intuition tells me that it is an
artifact of the process and that the use case I describe didn't come
up during the specification process.

Thoughts?

Thanks,
Tim



On Tue, Sep 11, 2012 at 12:32 PM, Michael Kay <mike@saxonica.com> wrote:
> Posting my reply to the list for completeness... MK
>
> On 11/09/2012 15:44, Michael Kay wrote:
>>
>>
>> Saxon is rejecting the schema because type X is not a restriction of type
>> Any; it is derived from Any, but some of the derivation steps involve
>> Extension.
>>
>> I believe this is correct according to the specification.
>>
>> Section 3.4.6 Constraints on Complex Type Definition Schema Components
>>
>> tells us that
>>
>> Schema Component Constraint: Derivation Valid (Restriction, Complex)
>>
>> must be satisfied in respect of types Z and Item1.
>>
>> Clause 5.4.2 of this constraint tells us:
>>
>> The particle of the complex type definition itself must be a ·valid
>> restriction· of the particle of the {content type} of the {base type
>> definition} as defined in Particle Valid (Restriction) (§3.9.6).
>>
>> Section 3.9.6 Particle Valid (Restriction) tells us the element particle
>> I-Data in Z must be a valid restriction of the element particle I-Data in
>> Item1. Under Particle Restriction OK (Elt:Elt - NameAndTypeOK) we learn in
>> clause 3.2.5 that this means
>>
>> 3.2.5 R's {type definition} is validly derived given {extension, list,
>> union} from B's {type definition} as defined by Type Derivation OK (Complex)
>> (§3.4.6) or Type Derivation OK (Simple) (§3.14.6), as appropriate.
>>
>> where R is type X and B is type Any.
>>
>> This takes us back to 3.4.6 which we execute with the parameter
>> {extension, list, union}.
>>
>> Rule 1 of 3.4.6 says
>>
>> 1 If B and D are not the same type definition, then the {derivation
>> method} of D must not be in the subset.
>>
>> But the subset includes "extension", so derivation by extension isn't
>> allowed; therefore it isn't a valid restriction.
>>
>> Michael Kay
>> Saxonica
>>
>>
>> On 11/09/2012 14:50, Timothy Cook wrote:
>>>
>>> <?xml version="1.0" encoding="UTF-8"?>
>>> <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema";
>>> elementFormDefault="qualified">
>>>      <xs:include schemaLocation="rm-test.xsd"/>
>>>
>>>      <xs:element name="CCD1" type="Y"/>
>>>
>>>      <xs:complexType name="Y">
>>>          <xs:complexContent>
>>>              <xs:restriction base="ccdType">
>>>                  <xs:sequence>
>>>                      <xs:element name="defin" type="Z"/>
>>>                  </xs:sequence>
>>>              </xs:restriction>
>>>          </xs:complexContent>
>>>      </xs:complexType>
>>>
>>>
>>>      <xs:complexType name="Z">
>>>          <xs:complexContent>
>>>              <xs:restriction base="Item1">
>>>                  <xs:sequence>
>>>                      <xs:element name="L-data" type="xs:string"
>>> fixed="My L string."/>
>>>                      <xs:element name="I-data" type="X"/>
>>>                  </xs:sequence>
>>>              </xs:restriction>
>>>          </xs:complexContent>
>>>      </xs:complexType>
>>>
>>>      <xs:complexType name="X">
>>>          <xs:complexContent>
>>>              <xs:restriction base="DT1-1">
>>>                  <xs:sequence>
>>>                      <xs:element name="A-data" type="xs:string"
>>> fixed="My A string."/>
>>>                      <xs:element name="dt-data" type="xs:string"
>>> fixed="A dt string."/>
>>>                  </xs:sequence>
>>>              </xs:restriction>
>>>          </xs:complexContent>
>>>      </xs:complexType>
>>>
>>>
>>>
>>>
>>> </xs:schema>
>>
>>
>



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