getting there, i think

schema/unix.xsd

@@ -6,7 +6,7 @@
            elementFormDefault="qualified"
            attributeFormDefault="qualified">
 
-    <xs:import schemaLocation="http://schema.xml.r00t2.io/linux.xsd"/>
+    <xs:import namespace="linux" schemaLocation="http://schema.xml.r00t2.io/linux.xsd"/>
 
     <xs:simpleType name="t_filepath">
         <xs:restriction base="xs:string">
@@ -51,7 +51,7 @@
                                   use="optional"/>
                 </xs:complexType>
                 <xs:unique name="uniq_grp">
-                    <xs:selector xpath="aif:xGroup"/>
+                    <xs:selector xpath="unix:xGroup"/>
                     <xs:field xpath="@name"/>
                 </xs:unique>
             </xs:element>