  In task-oriented dialogue systems, spoken language understanding, or SLU,
refers to the task of parsing natural language user utterances into semantic
frames. Making use of context from prior dialogue history holds the key to more
effective SLU. State of the art approaches to SLU use memory networks to encode
context by processing multiple utterances from the dialogue at each turn,
resulting in significant trade-offs between accuracy and computational
efficiency. On the other hand, downstream components like the dialogue state
tracker (DST) already keep track of the dialogue state, which can serve as a
summary of the dialogue history. In this work, we propose an efficient approach
to encoding context from prior utterances for SLU. More specifically, our
architecture includes a separate recurrent neural network (RNN) based encoding
module that accumulates dialogue context to guide the frame parsing sub-tasks
and can be shared between SLU and DST. In our experiments, we demonstrate the
effectiveness of our approach on dialogues from two domains.
