The post from James McGovern[duckdown.blogspot.com] on federated authorization resulted in response from Pat Patterson[blogs.sun.com] and Paul Madsen[connectid.blogspot.com]. First of all I would like to really thank Paul for providing the link to one of the best docs on entitlements that is out there i.e. Conceptual Grid Authorization Framework and Classification[gridforum.org]. It should be a required reading for all the people who enter in to this domain.
But at the same time, I am disappointed that Paul missed another approach mentioned in the document ( or may be I am missing something). Pat rightly identified the 2 typical models that can be implemented and Paul extended it by coming up with all the permutation and combinations using various components. But all the model discussed look to be various permutation of just one model i.e. Authorization Pull Model where the resource is resposible to connect to the Decision Point to get the result. I think a hybrid of the "Authorization Push Model" and Local policy evaluation is more appropriate for the federation model where along with the identity the authorization of subject itself will flow to the other domain. This is approach is defined by SecPAL[research.microsoft.com] (I hope this will become more mainstream and discussed in near future). In addition to that I would like to see more discussion on other policy languages beside XACML including Cassandra and SecPAL.
Another good point raised by James is the concept of relationship and how that should be part of the identity domain. With the rise of social networking this is a good usecase for the internet identity solutions like openID to solve. I do not think that this is a tough problem and I think that it can be solved by mapping it to an attribute or contextual role problem (similar to who has approver role in the context of given user which everybody is trying to solve in provisioning). But it is important to bring in a standard process for trust establishment and standardize the way in which the relationship are shared between various platforms.
My thoughts on the integration scenarios in next few days.