[XML-SIG] a small question

[Michael Sobolev]

Is this declaration is valid?

    <!ENTITY % lang.params "lang   CDATA #REQUIRED">
    <!ELEMENT comment (#PCDATA)>
    <!ATTLIST comment
        %lang.params;>

If no, what exactly is incorrect?  If yes, why xmlproc does not process
it properly? :)

TIA,

--
Mike