Deriving a simpleContent element from an anyType or anySimpleType

This one comes up in various guises from time to time.  
I think I know the answer but I want to check.  

It is desirable to be able to define a type by restriction 
of an abstract type so that the content model is various specific
simpleTypes.  
One model pattern that was proposed goes like this.  Start with:

<xs:complexType name="baseType" abstract="true">
  <xs:attribute name="a1" type="string">
</xs:complexType>

which is an (empty) "anyType" by implication.  
Then "restrict" the content to be simpleContent.  e.g.:

<xs:complexType name="integerType">
   <xs:simpleContent>
     <xs:restriction base="baseType">
       <xs:simpleType>
         <xs:restriction base="xs:integer"/>
       </xs:simpleType>
     </xs:restriction>
   </xs:simpleContent>
</xs:complexType>

to get an integer with an attribute, and   

<xs:complexType name="stringType">
   <xs:simpleContent>
     <xs:restriction base="baseType">
       <xs:simpleType>
         <xs:restriction base="xs:string"/>
       </xs:simpleType>
     </xs:restriction>
   </xs:simpleContent>
</xs:complexType>

to get a string with the same attribute.  

Problem is, this appears to violate the third sub-clause of  
http://www.w3.org/TR/xmlschema-2/#defn-rep-constr 

Am I reading this right?  

So: is there a way to accomplish what I'm trying do here? 
(i.e. have various simpleContent types inherit the same 
attribute, and sit within a single type-derivation hierarchy, 
and thus be able to support elements that fit in a substitutionGroup.)  

This might also be related to an exchange from last year:  

> -----Original Message-----
> From: Priscilla Walmsley [mailto:priscilla@walmsley.com]
> Sent: Saturday, 20 October 2001 1:02 AM
> To: 'Jeni Tennison'; 'Priscilla Walmsley'
> Cc: xmlschema-dev@w3.org
> Subject: RE: constraining an element to be either simple or complex
> content
> 
> 
> Hi Jeni,
> 
> That's a good point, and I think we may have uncovered a 
> contradiction in
> the Rec.  The section I was looking at is Derivation Valid 
> (Restriction,
> Complex) in clause 5:
> 
> 5.1 If the {content type} of the complex type definition is a 
> simple type
> definition, then one of the following must be true:
> 5.1.1 The {content type} of the {base type definition} must 
> be a simple type
> definition of which the {content type} is a ·valid 
> restriction· as defined
> in Derivation Valid (Restriction, Simple) (§3.14.6).
> 5.1.2 The {base type definition} must be mixed and have a 
> particle which is
> ·emptiable· as defined in Particle Emptiable (§3.9.6).
> 
> Unless maybe I should have used "complexContent"?  I will investigate
> further....
> 
> Priscilla
> -----------------------------------------------------------
> Priscilla Walmsley                   priscilla@walmsley.com
> Vitria Technology                     http://www.vitria.com
> Author, Definitive XML Schema    (Prentice Hall, Dec. 2001)
> -----------------------------------------------------------
> 
> > -----Original Message-----
> > From: Jeni Tennison [mailto:jeni@jenitennison.com]
> > Sent: Friday, October 19, 2001 12:44 PM
> > To: Priscilla Walmsley
> > Cc: xmlschema-dev@w3.org
> > Subject: Re: constraining an element to be either simple or complex
> > content
> >
> >
> > Hi Priscilla,
> >
> > > You can't extend simple content to create complex content, but you
> > > _can_ restrict mixed complex content to create simple content. In
> > > this situation, you would define the types as:
> > >
> > > <xs:complexType name="baseType" mixed="true" abstract="true">
> > >   <xs:sequence>
> > >     <xs:any minOccurs="0" maxOccurs="unbounded"/>
> > >   </xs:sequence>
> > > </xs:complexType>
> > >
> > > <xs:complexType name="simpleType">
> > >   <xs:simpleContent>
> > >     <xs:restriction base="baseType">
> > >       <xs:simpleType>
> > >         <xs:restriction base="xs:integer"/>
> > >       </xs:simpleType>
> > >     </xs:restriction>
> > >   </xs:simpleContent>
> > > </xs:complexType>
> >
> > Wow, that is obscure! It works in XSV, but I'm confused about why,
> > because Clause 2 of the Complex Type Definition Representation OK
> > Schema Representation Constraint says:
> >
> >   2 If the <simpleContent> alternative is chosen, the type
> >     definition ·resolved· to by the ·actual value· of the base
> >     [attribute] must be either a complex type definition whose
> >     {content type} is a simple type definition or, only if the
> >     <extension> alternative is also chosen, a simple type 
> definition;
> >
> > but the base attribute in the definition of the 
> 'simpleType' type is a
> > complex type definition whose {content type} is a *complex* type
> > definition, isn't it?
> >
> > Or am I reading it wrong?
> >
> > Cheers,
> >
> > Jeni
> >
> > ---
> > Jeni Tennison
> > http://www.jenitennison.com/
> >
> >
>

Received on Wednesday, 9 January 2002 02:11:11 UTC