<ds:Signature/> and <Signature/>

Hi,

 I looking at signature interoperability between C which is using
libxml2 (v 2.6.24) and Java using Apache's xml-security libs.  When I
sign the same document using the same key on same document.  The digest
match, but the signature values are different?

 Also the C lib is signing with the signature element <Signature
xmlns="http://www.w3.org/2000/09/xmldsig#"> whereas Java's signature
element is: <ds:Signature
xmlns:ds="http://www.w3.org/2000/09/xmldsig#">.  

Thanks,
Amritpal.