Question about the document style message part example in Ivan's study guide

[Umesh Balasubramaniam]

This study guide has been very helpful. I am reading the May 22, 2010 version of the guide and I have a question about the example on page 71.

   
<?xml version="1.0" encoding="UTF-8"?>
<definitions name="PurchaseOrderWS"
 targetNamespace="http://www.somedomain.com/xyz/PO"
 xmlns:sd="http://www.somedomain.com/xyz/PO"
 xmlns:soapbind="http://schemas.xmlsoap.org/wsdl/soap/"
 xmlns:xsd="http://www.w3.org/2001/XMLSchema"
 xmlns="http://schemas.xmlsoap.org/wsdl/">
  <types>
    <xsd:schema targetNamespace="http://www.somedomain.com/xyz/PO">
      <!-- Import the PurchaseOrder XML schema document -->
      <xsd:import namespace="http://www.somedomain.com/xyz/PO"
       schemaLocation="http://www.somedomain.com/xyz/po.xsd" />
    </xsd:schema>
  </types>
  <message name="SubmitPurchaseOrderMessage">
    <part name="order" element="sd:purchaseOrder" />
  </message>
  ...
</definitions>

 

In the above case the xsd:import statement is importing to the same namespace as the xsd:schema targetnamespace. Is this valid? I was reading on page 69 below the following example:

    
<types>
    <xsd:schema targetNamespace="http://www.somedomain.com/xyz/BookQuote">
         <!-- The ISBN simple type -->
         <xsd:simpleType name="ISBN">
             <xsd:restriction base="xsd:string">
                 <xsd:pattern value="[0-9]{9}[0-9Xx]" />
             </xsd:restriction>
         </xsd:simpleType>
    </xsd:schema>
    <xsd:schema>
         <xsd:import namespace="http://www.example.com/SpaceWarGame"
             schemaLocation="SpaceWarGame.xsd"/>
    </xsd:schema>
</types>
<!-- Note how the ISBN type declared above is used. -->
<message name="GetBookPriceRequest">
    <part name="isbn" type="sd:ISBN" />
</message>

Note that the <schema> element containing the XML schema <import> element does not specify a
targetNamespace. This because an <import> element cannot import another XML schema into a
schema with the same namespace. Also note that the <import> element is qualified by the XML
schema namespace prefix!

Thanks in advance.

[Ivan Krizsan]

Hi!
I'll take a look at this tomorrow and get back to you. I suspect that you may have found a mistake of mine, which I am very grateful for!
Best wishes!

[Ivan Krizsan]

Hi!
I cannot, at the moment, find the motivation to why having written what you quoted from page 69.
The best I have been able to find, so far, is a quote from the WS-I Basic Profile:

R2105 All xsd:schema elements contained in a wsdl:types element of a DESCRIPTION MUST have a targetNamespace attribute with a valid and non-null value, UNLESS the xsd:schema element has xsd:import and/or xsd:annotation as its only child element(s).

This does of course not say why the targetNamespace attribute should not be included on the <xsd:import> element.
I will continue my research.
Best wishes!

[Umesh Balasubramaniam]

Take a look at http://www.w3.org/TR/2004/REC-xmlschema-1-20041028/structures.html#element-import. They do mention this in the "Schema Representation Constraint: Import Constraints and Semantics" section:

If the namespace [attribute] is present, then its ·actual value· must not match the ·actual value· of the enclosing <schema>'s targetNamespace [attribute]

Based purely on the schema specification you don't really need the nested xsd:schema because there is no conflict with the targetNamespace attribute in the parent schema tag:

    
<types>
    <xsd:schema targetNamespace="http://www.somedomain.com/xyz/BookQuote">
         <!-- The ISBN simple type -->
         <xsd:simpleType name="ISBN">
             <xsd:restriction base="xsd:string">
                 <xsd:pattern value="[0-9]{9}[0-9Xx]" />
             </xsd:restriction>
         </xsd:simpleType>
    </xsd:schema>
    <xsd:schema>
         <xsd:import namespace="http://www.example.com/SpaceWarGame"
             schemaLocation="SpaceWarGame.xsd"/>
    </xsd:schema>
</types>

But on page 71, either you need to remove the targetNamespace from the schema tag or the targetNamespace has to be different from the import namespace:

    
<types>
  <xsd:schema targetNamespace="http://www.somedomain.com/xyz/PO">
    <!-- Import the PurchaseOrder XML schema document -->
    <xsd:import namespace="http://www.somedomain.com/xyz/PO"
     schemaLocation="http://www.somedomain.com/xyz/po.xsd" />
  </xsd:schema>
</types>

[Ivan Krizsan]

Hi again!
Yes, I am beginning to suspect that I wrote the example on page 71 without thinking about what I, at that time, just had written on page 69.
It does not make much sense to have a targetNamespace on the <xsd:schema> element in the <wsdl:types> element, if the only child element is a <xsd:import> element.
Thus, my conclusion is that there is an error on page 71. I will correct this in the next version of my study notes.
Thanks a lot for pointing this error out to me and for your patience awaiting my reply in this matter.
Best wishes!