default namespace = "http://www.w3.org/2001/XInclude"
namespace xi = "http://www.w3.org/2001/XInclude"

xi.include.attlist =
   attribute href     { xsd:anyURI }?,
   attribute parse    { "xml" | "text" }?,
   attribute xpointer { xsd:string }?,
   attribute encoding { xsd:string }?,
   attribute accept   { xsd:string }?,
   attribute accept-language { xsd:string }?

xi.include.attlist.extra =
   attribute * - xi.include.attlist { text }*

xi.include =
   element xi:include {
      xi.include.attlist,
      xi.include.attlist.extra,
      (xi.fallback? | xi.include.extra)*
   }

xi.include.extra = notAllowed

xi.fallback.attlist =
   attribute * { text }*

xi.fallback =
   element xi:fallback {
      xi.fallback.attlist, 
      (xi.include | xi.fallback.extra)*
   }

xi.fallback.extra = notAllowed

xi.class = xi.include | xi.fallback