XPath Transforms Deprecated in SAML 2.0

http://docs.oasis-open.org/security/saml/v2.0/saml-core-2.0-os.pdf

Reading this relatively recent document I get the impression that the XPath stuff that once were developed for use with XML Signatures, caused problems.

The document says that enveloped-signature and exclusive canonicalization are the only Transform elements that a receiver MUST recognize.

Although I prefer XPath as you can get away from ID tags and not have to worry about collisions, I guess that for a new standards effort, it would be foolish not to build on the experiences with SAML.

I have one question though: Can anybody explain what InclusuveAttributes does and what happens if it is not specified?  What prefixes should be specified?  Those that are a part of the signed message?

Anders Rundgren