  Most prior work on task-oriented dialogue systems are restricted to a limited
coverage of domain APIs, while users oftentimes have domain related requests
that are not covered by the APIs. In this paper, we propose to expand coverage
of task-oriented dialogue systems by incorporating external unstructured
knowledge sources. We define three sub-tasks: knowledge-seeking turn detection,
knowledge selection, and knowledge-grounded response generation, which can be
modeled individually or jointly. We introduce an augmented version of MultiWOZ
2.1, which includes new out-of-API-coverage turns and responses grounded on
external knowledge sources. We present baselines for each sub-task using both
conventional and neural approaches. Our experimental results demonstrate the
need for further research in this direction to enable more informative
conversational systems.
