Interactive spoken content retrieval by extended query model and continuous state space Markov Decision Process

Interactive retrieval is important for spoken content because the retrieved spoken items are not only difficult to be shown on the screen but also scanned and selected by the user, in addition to the speech recognition uncertainty. The user cannot playback and go through all the retrieved items to find out what he is looking for. Markov Decision Process (MDP) was used in a previous work to help the system take different actions to interact with the user based on an estimated retrieval performance, but the MDP state was represented by the less precise quantized retrieval performance metric. In this paper, we consider the retrieval performance metric as a continuous state variable in MDP and optimize the MDP by fitted value iteration (FVI).We also use query expansion with the language modeling retrieval framework to produce the next set of retrieval results. Improved performance was found in the preliminary experiments.