Oracle SQL Function XMLISVALID returns allways 0

Question

knows someone why this statement delivers me the result 0 and not 1

SELECT XMLISVALID( XMLType('<Termin Nr="498">
                           <Beginn>10.06.03</Beginn>
                           <Ende>13.06.03</Ende>
                           <Kurs>1015068</Kurs>
                        </Termin>'),
                XMLType('<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified">
                <xs:element name="Termin">
                   <xs:complexType>
                      <xs:sequence>
                         <xs:element name="Beginn" type="xs:string"/>
                         <xs:element name="Ende" type="xs:string"/>
                         <xs:element name="Kurs" type="xs:int"/>
                       </xs:sequence>
                       <xs:attribute name="Nr" type="xs:short" use="required"/>
                    </xs:complexType>
                 </xs:element></xs:schema>'))
FROM dual;

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