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Re: Problem w/ Schema for elements with similar defs

  • From: Eddie Robertsson <eddie@a...>
  • To: José Manuel Beas <jmbeas@t...>
  • Date: Mon, 08 Jan 2001 17:05:52 +1100
xsd extends
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> But this is the core of my problem. I'd like to "declare" an "object class"
> named "recurso" wich has a lot in common with "consulta". But they are not
> the same "class", "consulta" is more than "recurso". The technical problem
> arises when I am trying to say that:
>
> Recurso ::= "<recurso" AttributesOfRecurso ">" (Texto)* "</recurso>"
> Consulta ::= "<consulta" AttributesOfRecurso ">" (Texto|Imagen)*
> "</consulta>"
>
> e.g.
> <consulta nombre="C1">
>   <imagen nombre="I1"/>
>   <texto nombre="T1"/>
>   <imagen nombre="I2"/>
> </consulta>
>
> But with the Schema mechanism "extension" like Jeff proposes I cannot write
> the former example because it is treated like:

Hi José

I think I'd better start of by saying that I've just entered the "wonderful"
world of XSD and this may not be the easiest solution but it should work for
you. I understand that you want to use the extension function due to the
similarities of the elements consulta and recurso but I agree with Henry that
it's probably better to use a the group function as suggested by Jeff. The
problem with the extension function is due to the content models of the
elements. Since the content model of recurso = texto* and the content model of
consulta = (texto | imagen)*. This means that you can't simply extend the
recurso type by adding a new element imagen. However, if you want to use the
extend function you can create a base type which only contains the common
attribute valor.

<xsd:complexType name="baseType">
    <xsd:attribute name="valor"/>
</xsd:complexType>

You can then extend this baseType by adding the element texto to the recurso
type and adding a choice of the elements texto and imagen to the consulta type
(using group).

   <xsd:group name="imagenOrTexto">
    <xsd:choice>
          <xsd:element ref="texto"/>
          <xsd:element ref="imagen"/>
      </xsd:choice>
   </xsd:group>

 <xsd:complexType name="recursoTipo">
    <xsd:complexContent>
       <xsd:extension base="baseType" >
          <xsd:sequence>
           <xsd:element ref="texto" minOccurs="0" maxOccurs="unbounded"/>
            </xsd:sequence>
         </xsd:extension>
      </xsd:complexContent>
   </xsd:complexType>

 <xsd:complexType name="consultaTipo">
    <xsd:complexContent>
       <xsd:extension base="baseType" >
          <xsd:sequence>
           <xsd:group ref="imagenOrTexto" minOccurs="0"
maxOccurs="unbounded"/>
            </xsd:sequence>
         </xsd:extension>
      </xsd:complexContent>
   </xsd:complexType>

You can find the complete schema at the end of the email but I don't think you
should use extension in this case. It's a complicated solution (at least the
one I came up with but maybe you can simplify it...) and I think it's much
easier to use the second solution suggested by Jeff (this schema is at the end
of the email as well).

/Eddie

XSD for the extension version:
------------------------------------------8<--------------------------------------------------------

<?xml version="1.0" encoding="ISO-8859-1"?>
<xsd:schema targetNamespace="http://www.telenium.es/XML"
xmlns:xsd="http://www.w3.org/2000/10/XMLSchema"
xmlns="http://www.telenium.es/XML" elementFormDefault="qualified"
attributeFormDefault="unqualified">

   <xsd:element name="pantallas">
    <xsd:complexType>
       <xsd:sequence>
          <xsd:element ref="pantalla" minOccurs="0" maxOccurs="unbounded"/>
         </xsd:sequence>
      </xsd:complexType>
   </xsd:element>

   <xsd:element name="pantalla">
    <xsd:complexType>
       <xsd:sequence>
         <xsd:element ref="parametros" minOccurs="0" maxOccurs="1"/>
            <xsd:element ref="dimensiones" minOccurs="1" maxOccurs="1"/>
            <!-- A reference to an abstract element that can either be consulta
or recurso -->
            <xsd:element ref="consultaAndRecurso" minOccurs="0"
maxOccurs="unbounded"/>
         </xsd:sequence>
         <xsd:attribute name="nombre"/>
      </xsd:complexType>
   </xsd:element>

   <xsd:element name="parametros">
    <xsd:complexType>
       <xsd:sequence>
          <xsd:element name="parametro" minOccurs="1" maxOccurs="unbounded">
             <xsd:complexType>
                <xsd:attribute name="nombre" type="xsd:string"
use="required"/>
               </xsd:complexType>
            </xsd:element>
         </xsd:sequence>
      </xsd:complexType>
   </xsd:element>

   <xsd:element name="dimensiones">
    <xsd:complexType>
       <xsd:attribute name="x" type="xsd:integer"/>
         <xsd:attribute name="y" type="xsd:integer"/>
      </xsd:complexType>
   </xsd:element>

 <!-- A new abstract element consultaAndRecurso is created -->
   <xsd:element name="consultaAndRecurso" abstract="true" type="baseType"/>

 <!-- The consulta element has the type consultaTipo and can be used as a
substitution for the abstract consultaAndRecurso element -->
   <xsd:element name="consulta" type="consultaTipo"
substitutionGroup="consultaAndRecurso"/>

 <!-- The recurso element has the type recursoTipo and can be used as a
substitution for the abstract consultaAndRecurso element -->
   <xsd:element name="recurso" type="recursoTipo"
substitutionGroup="consultaAndRecurso"/>

<!-- The type baseType is used as base for the derivation of the two types
consultaTipo and recursoTipo. The baseType only contains the attribute valor.
-->
 <xsd:complexType name="baseType">
    <xsd:attribute name="valor"/>
 </xsd:complexType>

<!-- A new group is created that contains either one texto element or one
imagen element -->
   <xsd:group name="imagenOrTexto">
    <xsd:choice>
          <xsd:element ref="texto"/>
          <xsd:element ref="imagen"/>
      </xsd:choice>
   </xsd:group>

 <!-- A new type is added for the recurso element called recursoTipo. This type
extends the baseType type by adding the element texto to the content model. -->

 <xsd:complexType name="recursoTipo">
    <xsd:complexContent>
       <xsd:extension base="baseType" >
          <xsd:sequence>
           <xsd:element ref="texto" minOccurs="0" maxOccurs="unbounded"/>
            </xsd:sequence>
         </xsd:extension>
      </xsd:complexContent>
   </xsd:complexType>

<!-- A new type is created for the consulta element called consultaTipo. This
type extends the baseType type by adding the group imagenOrTexto to the content
model -->
 <xsd:complexType name="consultaTipo">
    <xsd:complexContent>
       <xsd:extension base="baseType" >
          <xsd:sequence>
           <xsd:group ref="imagenOrTexto" minOccurs="0" maxOccurs="unbounded"/>

            </xsd:sequence>
         </xsd:extension>
      </xsd:complexContent>
   </xsd:complexType>

   <xsd:element name="texto">
    <xsd:complexType>
       <xsd:attributeGroup ref="componenteBasico"/>
      </xsd:complexType>
   </xsd:element>

   <xsd:element name="imagen">
    <xsd:complexType>
       <xsd:attributeGroup ref="componenteBasico"/>
         <xsd:attribute name="x" type="xsd:integer"/>
         <xsd:attribute name="y" type="xsd:integer"/>
      </xsd:complexType>
   </xsd:element>

   <xsd:attributeGroup name="componenteBasico">
    <xsd:attribute name="nombre" type="xsd:string"/>
      <xsd:attribute name="ancho" type="xsd:integer"/>
      <xsd:attribute name="alto" type="xsd:integer"/>
   </xsd:attributeGroup>
</xsd:schema>
--------------------------------------------------------------------------

XSD for the second solution using groups:
------------------------------------------8<--------------------------------------------------------

<?xml version="1.0" encoding="ISO-8859-1"?>
<xsd:schema targetNamespace="http://www.telenium.es/XML"
xmlns:xsd="http://www.w3.org/2000/10/XMLSchema"
xmlns="http://www.telenium.es/XML" elementFormDefault="qualified"
attributeFormDefault="unqualified">

   <xsd:element name="pantallas">
    <xsd:complexType>
       <xsd:sequence>
          <xsd:element ref="pantalla" minOccurs="0" maxOccurs="unbounded"/>
         </xsd:sequence>
      </xsd:complexType>
   </xsd:element>

   <xsd:element name="pantalla">
    <xsd:complexType>
       <xsd:sequence>
         <xsd:element ref="parametros" minOccurs="0" maxOccurs="1"/>
          <xsd:element ref="dimensiones" minOccurs="1" maxOccurs="1"/>
        <!-- Then refer to the group and make it unbounded -->
        <xsd:group ref="consultaAndRecurso" minOccurs="0"
maxOccurs="unbounded"/>
         </xsd:sequence>
         <xsd:attribute name="nombre"/>
      </xsd:complexType>
   </xsd:element>

   <xsd:element name="parametros">
    <xsd:complexType>
       <xsd:sequence>
          <xsd:element name="parametro" minOccurs="1" maxOccurs="unbounded">
             <xsd:complexType>
                <xsd:attribute name="nombre" type="xsd:string"
use="required"/>
               </xsd:complexType>
            </xsd:element>
         </xsd:sequence>
      </xsd:complexType>
   </xsd:element>

   <xsd:element name="dimensiones">
    <xsd:complexType>
       <xsd:attribute name="x" type="xsd:integer"/>
         <xsd:attribute name="y" type="xsd:integer"/>
      </xsd:complexType>
   </xsd:element>

   <!-- A new group is created that contains either one consulta element or one
recurso element -->
 <xsd:group name="consultaAndRecurso">
    <xsd:choice>
     <xsd:element name="consulta" type="consultaTipo" />
      <xsd:element name="recurso" type="recursoTipo" />
    </xsd:choice>
 </xsd:group>

   <!-- A new group is created that contains either one texto element or one
imagen element -->
   <xsd:group name="imagenOrTexto">
    <xsd:choice>
          <xsd:element ref="texto"/>
          <xsd:element ref="imagen"/>
      </xsd:choice>
   </xsd:group>

 <!-- A new type is created for the recurso element called recursoTipo. -->
 <xsd:complexType name="recursoTipo">
    <xsd:sequence>
     <xsd:element ref="texto" minOccurs="0" maxOccurs="unbounded"/>
      </xsd:sequence>
      <xsd:attribute name="valor"/>
   </xsd:complexType>

 <!-- A new type is added for the consulta element called consultaTipo. -->
 <xsd:complexType name="consultaTipo">
    <xsd:sequence>
     <xsd:group ref="imagenOrTexto" minOccurs="0" maxOccurs="unbounded"/>
      </xsd:sequence>
      <xsd:attribute name="valor"/>
   </xsd:complexType>

   <xsd:element name="texto">
    <xsd:complexType>
       <xsd:attributeGroup ref="componenteBasico"/>
      </xsd:complexType>
   </xsd:element>

   <xsd:element name="imagen">
    <xsd:complexType>
       <xsd:attributeGroup ref="componenteBasico"/>
         <xsd:attribute name="x" type="xsd:integer"/>
         <xsd:attribute name="y" type="xsd:integer"/>
      </xsd:complexType>
   </xsd:element>

   <xsd:attributeGroup name="componenteBasico">
    <xsd:attribute name="nombre" type="xsd:string"/>
      <xsd:attribute name="ancho" type="xsd:integer"/>
      <xsd:attribute name="alto" type="xsd:integer"/>
   </xsd:attributeGroup>
</xsd:schema>

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