Accommodating a question onto QUD

Dialogue participants can address questions that have not been explicitly raised in the dialogue. However, it is important that a question be available to the agent who is to interpret it because the utterance may be elliptical. Here is an example from our dialogue:

$J: vicken månad ska du åka
( what month do you want to go )
$P: ja: typ den: ä: tredje fjärde april /
nån gång där
( well around 3rd 4th april / some time there )
$P: så billit som möjlit
( as cheap as possible )

The strategy we adopt for interpreting elliptical utterances is to think of them as short answers (in the sense of Ginzburg [Ginzburg1998]) to questions on QUD. A suitable question here is What kind of price does P want for the ticket?. This question is not under discussion at the point when P says ``as cheap as possible''. But it can be figured out since J knows that this is a relevant question. In fact it will be a question which J has as an action in his plan to raise. On our analysis it is this fact which enables A to interpret the ellipsis. He finds the matching question on his plan, accommodates by placing it on QUD and then continues with the integration of the information expressed by as cheap as possible as normal. Note that if such a question is not available then the ellipsis cannot be interpreted as in the dialogue in (7).

A. What time are you coming to pick up Maria?
B. Around 6 p.m. As cheap as possible.

This dialogue is incoherent if what is being discussed is when the child Maria is going to be picked up from her friend's house (at least under standard dialogue plans that we might have for such a conversation).