purpose of the policy engine?

[tlodderstedt]

What is the purpose of the policy engine between protocols and objects? I think a protocol implementation needs to be able to query available objects and object types (typically based on request data, e.g. credential types). How is this facilitated?

[OR13]

We didn't get to this topic on the last call.

I think the objective for it, is to be able to profile away from certain parts of interop... for example, maybe your wallet does not support ES256K, because you don't allow non FIPSs crypto, etc...