Probabilistic hyperspace analogue to language Leif Azzopardi, Mark Girolami, and Malcolm K. Crowe   View Paper (PDF)   Return to Posters Abstract to generate higher order concepts which are later used for ad-hoc retrieval. In this poster, we propose an alternative implementation of the conceptual space by using a probabilistic HAL space (pHAL). To evaluate whether converting to such an implementation is beneficial we have performed an initial investigation comparing the concept combination of HAL against pHAL for the task of query expansion. Our experiments indicate that pHAL outperforms the original HAL method and that better query term selection methods can improve performance on both HAL and pHAL. ©2006 Association for Computing Machinery