sig
  type physical_dom_type = PT_CursorSeq | PT_ListSeq
  type physical_sax_type = PT_Stream | PT_Discarded
  type physical_xml_type =
      PT_Dom of Xquery_physical_type_ast.physical_dom_type
    | PT_Sax of Xquery_physical_type_ast.physical_sax_type
  type physical_variable_type =
      Xquery_common_ast.cvname * Xquery_physical_type_ast.physical_xml_type
  type physical_tuple_field_type =
      Xquery_common_ast.crname * Xquery_physical_type_ast.physical_xml_type
  type physical_tuple_type =
      Xquery_physical_type_ast.physical_tuple_field_type list
  type physical_type =
      PT_XML of Xquery_physical_type_ast.physical_xml_type
    | PT_Table of Xquery_physical_type_ast.physical_tuple_type
end