targetNamespace and default namespace

[Elliotte Rusty Harold <elharo@ibiblio.org>]

In Eclipse plug-ins we encounter W3C XML Schemas like the following:

<?xml version='1.0' encoding='UTF-8'?>
<!-- Schema file written by PDE -->
<schema targetNamespace="com.google.cloud.tools.eclipse.appengine.libraries"
xmlns="http://www.w3.org/2001/XMLSchema";>
  <element name="extension">
      <complexType>
         <choice minOccurs="1" maxOccurs="unbounded">
            <element ref="library" />
         </choice>
         <attribute name="point" type="string" use="required" />
         <attribute name="id" type="string" />
         <attribute name="name" type="string">
            <annotation>
               <appinfo>
                  <meta.attribute translatable="true" />
               </appinfo>
            </annotation>
         </attribute>
      </complexType>
   </element>
...

Note in particular:

1. elementFormDefault is not specified. Therefore it takes the default
value of unqualified.
2. extension is defined by a top-level element. Therefore the
targetNamespace applies and extension is defined only in the namespace
com.google.cloud.tools.eclipse.appengine.libraries
3. The library element is a child of extension and therefore the
targetNamespace does not apply.

Note the use of a Java package name as a target namespace. That's not
recommended, but what's more shocking are the instance documents this
describes. They look like this:

<?xml version="1.0" encoding="UTF-8"?>
<?eclipse version="3.4"?>
 <plugin>
  <extension-point
id="com.google.cloud.tools.eclipse.appengine.libraries" name="App
Engine Libraries"
schema="schema/com.google.cloud.tools.eclipse.appengine.libraries.exsd"/>

Note the complete lack of namespace declarations. In itself this is
not a problem. Documents don't have to use namespaces. However, if I'm
reading the schema spec correctly, this means that this document is
invalid according to the schema. Am I correct? The schema spec is
quite opaque on these matters.

In more generic terms if a schema declares a target namespace, and
elementFormDefault="unqualified", then top-level elements defined in
the schema should be in the targetNamespace. Am I readin this right?

FWIW, I'm primarily concerned with elements here. The extra
complexities of attributes aren't immediately relevant.

-- 
Elliotte Rusty Harold
elharo@ibiblio.org