[xml] Schema validation fails with global definitions

[Israel Ganor <ganor softlink com>]

Validating this simple file using xmlSchemaValidateDoc() (Windows libxml
2.6.7) always gives the error "Element USER content check failure":

<BHUB-ADMIN xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance";
xsi:noNamespaceSchemaLocation="BrainSchema.xsd">
        <USER ACTION="modify">
                <METHODS>5</METHODS>
        </USER>
</BHUB-ADMIN>

The schema fragment looks as follows:
--------------------------------------------------------
<xs:element name="BHUB-ADMIN">
        <xs:complexType>
                <xs:sequence>
                        <xs:element ref="USER"/>
                </xs:sequence>
        </xs:complexType>
</xs:element>
<xs:element name="METHODS" type="xs:byte"/>
<xs:element name="USER">
        <xs:complexType>
                <xs:sequence>
                        <xs:element ref="METHODS"/>
                </xs:sequence>
                <xs:attribute name="ACTION"/>
        </xs:complexType>
</xs:element>

Te error is resolved if I replace the global definition of USER (<xs:element
ref="USER"/>) by a local definition as follows:
----------------------------------------------------------------------------
----------------
<xs:element name="BHUB-ADMIN">
        <xs:complexType>
                <xs:sequence>
                        <xs:element name="USER">
                                <xs:complexType>
                                        <xs:sequence>
                                                <xs:element ref="METHODS"/>
                                        </xs:sequence>
                                        <xs:attribute name="ACTION"/>
                                </xs:complexType>
                        </xs:element>
                </xs:sequence>
        </xs:complexType>
</xs:element>
<xs:element name="METHODS" type="xs:byte"/>


Doesn't libxml2 support global elements?
This is a great problem for me since I have huge schemas with complex
hierarchy, and many of the elements are common and referenced from several
elements.

Thanks in advance

Israel Ganor