RIF: How much XML Signature is mature?

>I'd just add in reference to Gino's original note that, I would expect that the web service he describes to >potentially encompass authorization, multi-reference and multiple digital signatures.  Even noting that >though XML Signature and SAML are comfortably mature, WS-Security is (hopefully) just about to give birth to >its first official standards, it would be a pretty safe bet that using an XML Signature/WS-Security/SAML(?) >architecture is going to be a lot less expensive and much more future-proof than a roll-your-own approach
 
Thank you for such a reference, Ed. 
 
I guess this has been a great discussion, too. 
 
Gino