  In order to interpret the communicative intents of an utterance, it needs to
be grounded in something that is outside of language; that is, grounded in
world modalities. In this paper, we argue that dialogue clarification
mechanisms make explicit the process of interpreting the communicative intents
of the speaker's utterances by grounding them in the various modalities in
which the dialogue is situated. This paper frames dialogue clarification
mechanisms as an understudied research problem and a key missing piece in the
giant jigsaw puzzle of natural language understanding. We discuss both the
theoretical background and practical challenges posed by this problem and
propose a recipe for obtaining grounding annotations. We conclude by
highlighting ethical issues that need to be addressed in future work.
