Re: redefine

[Eddie Robertsson <eddie@allette.com.au>]

Hi Dan,

I'll do my best to answer your questions about redefine and I think the most important thing to remember about redefine is that (as described in the Primer [1]), once a type has been redefined, the redefined type applies to all schema components that make use of the type.

So... (see comments inline)
[1] http://www.w3.org/TR/xmlschema-0/#Redefine

<?xml version="1.0" encoding="UTF-8"?>
<xsd:schema targetNamespace="namespace" xmlns="namespace" xmlns:xsd="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified">
<xsd:complexType name="top" abstract="true"/>
<xsd:complexType name="middle">
   <xsd:complexContent>
     <xsd:extension base="top"/>
   </xsd:complexContent>
</xsd:complexType>
</xsd:schema>

lower_level.xsd:

<?xml version="1.0" encoding="UTF-8"?>
<xsd:schema targetNamespace="namespace" xmlns="namespace" xmlns:xsd="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified">
<xsd:redefine schemaLocation="Z:\XML\upper_level.xsd">
  <xsd:complexType name="top">
    <xsd:complexContent>
      <xsd:extension base="top">
        <xsd:sequence>
          <xsd:element name="number" type="xsd:int"/>
        </xsd:sequence>
      </xsd:extension>
    </xsd:complexContent>
  </xsd:complexType>

  <xsd:complexType name="bottom">
    <xsd:complexContent>
      <xsd:extension base="middle"/>
    </xsd:complexContent>
  </xsd:complexType>
</xsd:redefine>
</xsd:schema>

This schema is not valid. Only the type/group that you want to redefine
should be within the <xsd:redefine> element. In this case you redefine
the top complexType so this is the only complexType that should appear
within redefine. So, move the complexType bottom outside the redefine element.
> Will
> an element of type bottom contain an element named number?
Yes
> Essentially,
> since middle extends top in upper_level.xsd, and top is redefined in lower_level.xsd
> will middle extend from this new redefinition of top, or still extend the
> older version?
Middle will extend from the redefinition of top

More importantly (for me anyway) if the following two Schemas also exist and are related to the first two:

---------------------------------
other_level.xsd

<?xml version="1.0" encoding="UTF-8"?>
<xsd:schema targetNamespace="namespace" xmlns="namespace" xmlns:xsd="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified">
  <xsd:include schemaLocation="Z:\XML\upper_level.xsd"/>
  <xsd:complexType name="ceiling">
    <xsd:sequence>
       <xsd:element name="up" type="top"/>
    </xsd:sequence>
  </xsd:complexType>
</xsd:schema>

final_level.xsd

<?xml version="1.0" encoding="UTF-8"?>
<xsd:schema targetNamespace="namespace" xmlns="namespace" xmlns:xsd="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified">
  <xsd:include schemaLocation="Z:\XML\lower_level.xsd"/>
  <xsd:include schemaLocation="Z:\XML\other_level.xsd"/>
    <xsd:element name="finalElement">
      <xsd:sequence>
        <xsd:element name="above" type="ceiling"/>
        <xsd:element name="floor" type="top"/>
      </xsd:sequence>
    </xsd:element>
</xsd:schema>
---------------------------------

This schema is missing the complexType element in the element declaration
of finalElement.
> Since
> upper_level.xsd is included through both other_level.xsd and lower_level.xsd
> by final_level.xsd will the complexType definition used to define the top
> complexType (that is the type for the floor element) be the one in upper_level.xsd
> or the redefined version lower_level.xsd?
The redefined version in lower_level.xsd
>  Also,
> since the above element references the ceiling complexType, which has an
> element of complexType top will this sub element (up) still be of the complexType
> top as defined in upper_level.xsd or will it automatically become of the
> complexType top redefined in lower_level.xsd (even though other_level.xsd
> makes no reference to lower_level.xsd)?
The redefined complexType in lower_level.xsd
> My
> guess is that anything new that reference top (either an element or an
> complexType that uses extension) will use the most *redefined*version.
Yes
> However,
> the up element will still be of complexType top as defined in upper_level.xsd.
No, this will also use the redefined type.

This means that a valid instance for your final_level schema would be:

<finalElement xmlns="namespace" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="namespace final_level.xsd">
  <above>
    <up>
      <number>1</number>
    </up>
  </above>
  <floor>
    <number>2</number>
  </floor>
</finalElement>
 

Cheers,
/Eddie