example1.xml

<?xml version="1.0" encoding="ISO-8859-1" ?>

<!DOCTYPE a [
<!ATTLIST a  att1  NMTOKENS  #IMPLIED
             att2  ID        #REQUIRED>
<!ATTLIST b  btt2  ID        #REQUIRED
             btt3  IDREF     #REQUIRED>
<!ELEMENT a  (b, cü?)>
<!ELEMENT b  EMPTY>
<!ELEMENT cü (#PCDATA)>
]>

<?pi a processing instruction?>

<a att1=" test
          äöüß
          test "
   att2="root"
>
    <b btt2="b1" btt3="root"/>
    <cü>hello world äöüß test</cü>
</a>