...or Why do these files validate in Visual Studio 2010 but not with xmllint1?

I'm currently working against a published xml schema where the original author's habit is to break down the schemas into several .xsd-files, but where some schema files have the same targetNamespace. Is this really "allowed"?

Example (extremely simplified):

File    targetNamespace    Contents
------------------------------------------------------------
b1.xsd  uri:tempuri.org:b  complex type "fooType"
b2.xsd  uri:tempuri.org:b  simple type "barType"

a.xsd   uri:tempuri.org:a  imports b1.xsd and b2.xsd
                           definition of root element "foo", that
                           extends "b:fooType" with an attribute
                           of "b:barType"

(Complete file contents below.)

Then I have an xml file, data.xml, with this content:

<?xml version="1.0"?>
<foo bar="1" xmlns="uri:tempuri.org:a" xmlns:xs="http://www.w3.org/2001/XMLSchema" />

For a long time, I have believed that all of this was correct, since Visual Studio apparently allows this schema style. However, today I decided to set up a command line utility for validating xml files, and I chose xmllint.

When I ran xmllint --schema a.xsd data.xml, I was presented with this warning:

a.xsd:4: element import: Schemas parser warning : Element '{http://www.w3.org/2001/XMLSchema}import': Skipping import of schema located at 'b2.xsd' for the namespace 'uri:tempuri.org:b', since this namespace was already imported with the schema located at 'b1.xsd'.

The fact that the import of b2.xsd was skipped obviously leads to this error:

a.xsd:9: element attribute:

xml schema xsd
Edit
Report