schema imports

[Cory Wilkerson]

Given the following WSDL document (obviously paraphrased):

<definitions xmlns:foo="foo" xmlns:bar="bar">
        <types>
                <schema targetNamespace="foo">
                        <complexType name="complexFoo">
                                <element name="elementFoo" type="bar:complexBar"/>
                        </complexType>
                </schema>
                <schema targetNamespace="bar">
                        <complexType name="complexBar">
                                ...
                        </complexType>
                <schema>
        </types>
      ...
<definitions>

Is the reference to element complexBar from namespace "bar" valid in namespace "foo" 
(when elementFoo is of type complexBar) or do I need an explicit schema import 
declaration and if so -- how is that done here?  I'm working with a vendor who is 
disputing the validity of WSDL formed much like this but Axis and .Net swallow the 
WSDL just fine and interact with my service just as I would expect.  

Futhermore, they're attempting to tell me that the namespace must reference something 
concrete.  Their assertions seem a bit cracked induced but I'm looking for someone to 
back me up here before I act the fool.

Thanks,
Cory Wilkerson