According to the specification for XInclude, processors must add an xml:base
      attribute to elements included from locations with a different base URI.  Without
      these attributes, the resulting infoset information would be incorrect.  Unfortunately,
      these attributes make XInclude processing not transparent to Schema validation.
     
     
      One solution to this is to modify your schema to allow xml:base
      attributes to appear on elements that might be included from different base URIs.
      There is a similar problem with xml:lang attributes that are added as a result
      of language fixup. If the addition of xml:base and/or xml:lang
      is undesired by your application, you can disable
      base URI fixup and 
      language fixup so that
      these attributes will not be added.