Question: Is there a standard way to compose an identifier for the public key of an object?

Hi all, 

I have a question. 

Is there a standard way to compose an identifier for the public key of
an object?

For example, it would be very nice if I can be assured that I will get a
public key for =bob by just doing =bob*(+public_key) or something. Then,
without any prior knowledge about =bob, I can fetch his public key for
bunch of processing. 

Cheers, 

Nat