Java Security

I am trying to write XML Digital signature code using xmldsig.jar from JAVA Web Services Developer Pack 2.0.

It works fine if I sign whole document. If I try to sign only reference..i.e. part of document by specifying URI while creatig Reference, it doesnt work. Its throwing below error...

Any light??? Thanks for your help...

javax.xml.crypto.dsig.XMLSignatureException: javax.xml.crypto.URIReferenceException: com.sun.org.apache.xml.internal.security.utils.resolver.ResourceResolverException: Could not find a resolver for URI /S:Envelope/S:Header/wsse:Security/saml:Assertion and Base /
at org.jcp.xml.dsig.internal.dom.DOMReference.dereference(DOMReference.java:366)
at org.jcp.xml.dsig.internal.dom.DOMReference.digest(DOMReference.java:278)
at org.jcp.xml.dsig.internal.dom.DOMXMLSignature.digestReference(DOMXMLSignature.java:441)
at org.jcp.xml.dsig.internal.dom.DOMXMLSignature.sign(DOMXMLSignature.java:337)
at GenEnveloped.main(GenEnveloped.java:130)
Caused by: javax.xml.crypto.URIReferenceException: com.sun.org.apache.xml.internal.security.utils.resolver.ResourceResolverException: Could not find a resolver for URI /S:Envelope/S:Header/wsse:Security/saml:Assertion and Base /
at org.jcp.xml.dsig.internal.dom.DOMURIDereferencer.dereference(DOMURIDereferencer.java:84)
at org.jcp.xml.dsig.internal.dom.DOMReference.dereference(DOMReference.java:358)
... 4 more
Caused by: com.sun.org.apache.xml.internal.security.utils.resolver.ResourceResolverException: Could not find a resolver for URI /S:Envelope/S:Header/wsse:Security/saml:Assertion and Base /
at com.sun.org.apache.xml.internal.security.utils.resolver.ResourceResolver.getInstance(Unknown Source)
at org.jcp.xml.dsig.internal.dom.DOMURIDereferencer.dereference(DOMURIDereferencer.java:75)
... 5 more
javax.xml.crypto.URIReferenceException: com.sun.org.apache.xml.internal.security.utils.resolver.ResourceResolverException: Could not find a resolver for URI /S:Envelope/S:Header/wsse:Security/saml:Assertion and Base /
at org.jcp.xml.dsig.internal.dom.DOMURIDereferencer.dereference(DOMURIDereferencer.java:84)
at org.jcp.xml.dsig.internal.dom.DOMReference.dereference(DOMReference.java:358)
at org.jcp.xml.dsig.internal.dom.DOMReference.digest(DOMReference.java:278)
at org.jcp.xml.dsig.internal.dom.DOMXMLSignature.digestReference(DOMXMLSignature.java:441)
at org.jcp.xml.dsig.internal.dom.DOMXMLSignature.sign(DOMXMLSignature.java:337)
at GenEnveloped.main(GenEnveloped.java:130)
Caused by: com.sun.org.apache.xml.internal.security.utils.resolver.ResourceResolverException: Could not find a resolver for URI /S:Envelope/S:Header/wsse:Security/saml:Assertion and Base /
at com.sun.org.apache.xml.internal.security.utils.resolver.ResourceResolver.getInstance(Unknown Source)
at org.jcp.xml.dsig.internal.dom.DOMURIDereferencer.dereference(DOMURIDereferencer.java:75)
... 5 more
javax.xml.crypto.URIReferenceException: com.sun.org.apache.xml.internal.security.utils.resolver.ResourceResolverException: Could not find a resolver for URI /S:Envelope/S:Header/wsse:Security/saml:Assertion and Base /
at org.jcp.xml.dsig.internal.dom.DOMURIDereferencer.dereference(DOMURIDereferencer.java:84)
at org.jcp.xml.dsig.internal.dom.DOMReference.dereference(DOMReference.java:358)
at org.jcp.xml.dsig.internal.dom.DOMReference.digest(DOMReference.java:278)
at org.jcp.xml.dsig.internal.dom.DOMXMLSignature.digestReference(DOMXMLSignature.java:441)
at org.jcp.xml.dsig.internal.dom.DOMXMLSignature.sign(DOMXMLSignature.java:337)
at GenEnveloped.main(GenEnveloped.java:130)
Caused by: com.sun.org.apache.xml.internal.security.utils.resolver.ResourceResolverException: Could not find a resolver for URI /S:Envelope/S:Header/wsse:Security/saml:Assertion and Base /
at com.sun.org.apache.xml.internal.security.utils.resolver.ResourceResolver.getInstance(Unknown Source)
at org.jcp.xml.dsig.internal.dom.DOMURIDereferencer.dereference(DOMURIDereferencer.java:75)
... 5 more
Exception in thread "main"