Let's avoid the word "credential". It has so many meanings as to be confusing

Today I re-viewed the Craig Mundie keynote from the RSA 2008 conference. Many things were said that I liked: Recently, a few weeks ago, we announced that we had acquired Credentica, and their U-Prove technology, which we think is going to be an example of a way to realize this requirement where we can tease apart some of the individual claims around identity or elements of identity and present them individually, and therefore be able to prove certain pieces of information without disclosing too much.

Stefan and his colleagues Christian Paquin and Greg Thompson have joined the Identity and Access Group at Microsoft

In the simplest case, you can just look at the identity payload as an XML blob posted to a web site

Here are the claims you can request when dealing with CardSpace self-issued cards