Attribute = "xattr" "[" "name" ":" String ","
   	                "class" ":" ("simple" / "general") ","
 		        "type" ":" String ","
		        "comm" ":" ("in" / "out" / "inter" / "comm") ","
		        "callback" ":" ForeignIdentifier ","
		        "abbrev" ":" String ","
		        "desc" ":" String "]" "."