On 2008/06/05, at 0:03, Martin Atkins wrote:

The scenario is that I have a preferred OP on the PC-class device that I like because, say, it has a hardware device attached to it for security purposes.

Now I'd like to log on, with the same identifier, from my iPhone that does not have the same hardware device attached: I will be redirected to the OP that then cannot authenticate me.

It would be better to say "I'd like OP1, but only for PCs, and OP2 for iPhones, ..." all somehow expressed in the XRDS file so the RP could do the redirect to the right OP based on which device I'm using, all while using the same identifier.

Of course, an OP that supports all devices and all the right authentication techniques appropriate for each device would be better. But that's a hard thing to do given how many possible combinations there are.