"X is asking for Y, wadda ya think?"
Beyond the simple yes/no, accept/deny, proceed/stop options (I've seen them all), there could be agreement on phrasing of the 'remember this decision' prompt and its options.
Alternatively (and far more work), how about a CCML 'Consent Context Markup Language' - a syntax describing how consent was obtained, comparable to SAML's Authentication Context and OpenID's Authentication Quality Extension for describing how authentication occurred.
Quick list of contexts.
- Who obtained consent? For what?
- How was the question phrased (as per above)?
- How was the question presented, e.g. by directly asking the user when they were 'at' the provider, or indirectly a la Liberty's Interaction Service , or by direct user-mediation of the flow a la Cardspace or SAML ECP? (hopefully avoiding the complexity of describing authentication because there would be no temptation to try and say that one consent mechanism was 'better' than another for ranking.)
- When was consent obtained, e.g. a priori, real-time?
Of course, the question is who would care? It would be the provider making the access control decision for a particular bit of identity that would need to know about consent, so in what scenarios is it relevant for the details of said consent to be recorded? Audit would be one. Supporting a 'User Dashboard' where a user can see past identity transactions (and the specifics of the corresponding consent) would be another.
No identity system does this, so nobody should (you'd think) have resistance to collaborating.