Focussing and plan recognition in negotiation dialogue

It is well known that focussed plan construction helps to reduce the number of plan recognition hypotheses to be considered by the hearer (see Section 2.5). However, the negotiation planner at present must entertain many different negotiation act hypotheses since they are not chosen by their relation to the subject of the previous negotiation act. It is clear from corpora of human dialogues for collaborative planning, for example the TRAINS corpus [33], that on the contrary, speakers move in a rigorously focussed way as they traverse the domain plan structure. For the sake of game trees with a manageable branching factor, and to improve the planner's performance in recognising noisy or elliptical input, a selection mechanism that penalises unfocused negotiation acts is proposed for future implementations of the planner.