It is a good question and one which along with many others, the Kantara Attribute Management Discussion Group has within its scope.
The general feeling is that 'responsibility' as you mention below, will be published/consumed via meta data.
But we need to determine what that actual attribute will be - whether we create one or re-use one (say from a SAML 2.0 profile).
> Date: Tue, 3 Jan 2012 19:43:50 +0100
> From: s172556@studenti.polito.it
> To: community@kantarainitiative.org
> Subject: [Kantara - Community] Attributes from multiple APs
>
> Hello everyone,
>
> I am starting a thesis work on attributes management and aggregation in
> a federated identity environment and I am trying to figure out how to
> address attributes resolution in a scenario where there are multiple
> Attribute Providers.
> The main issue is: how does a relying party know which AP is responsible
> for a given attribute?
> As I am doing a research, I would like to know if in Kantara this
> problem has been faced and, if so, how you have solved it.
>
> Thank you for your time and consideration.
>
> Best Regards,
>
> Mauro
>
> --
> Mauro L
> Polytechnic University of Turin
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