18. A computer-readable storage device having instructions stored which, when executed on a computing device, cause the computing device to perform operations comprising: receiving, from a user, a visual reference to a specific entity in a known domain, where an identity of the specific entity is unknown; extracting a visual context from a domain-specific training data associated with the known domain; determining the identity of the specific entity using the visual reference in combination with one of a speaker history, the visual context, and speaker preferences; and generating a text expression referring to the specific entity based on the identity of the specific entity.
20. The computer-readable storage device of claim 18 , wherein a weighted finite-state automaton represents partial orderings of word pairs in the domain-specific training data.