Message Oracle LPX-00102 - standalone document declaration should be no

ERRORstandalone document declaration should be no
CAUSEValidity Constraint 2.9 failed: Standalone document declaration must have the value no if any external markup declarations contain declarations of: * attributes with default values - or - * entities - or - * attributes with values subject to normalization - or - * element types with element content
ACTIONCorrect the document.