Collaboration on reference to objects that are not mutually known
  In conversation, a person sometimes has to refer to an object that is not previously known to the other participant. We present a plan-based model of how agents collaborate on reference of this sort. In making a reference, an agent uses the most salient attributes of the referent. In understanding a reference, an agent determines his confidence in its adequacy as a means of identifying the referent. To collaborate, the agents use judgment, suggestion, and elaboration moves to refashion an inadequate referring expression. 
Philip G. Edmonds