  Multimodal interfaces that combine direct manipulation and natural language
have shown great promise for data visualization. Such multimodal interfaces
allow people to stay in the flow of their visual exploration by leveraging the
strengths of one modality to complement the weaknesses of others. In this work,
we introduce an approach that interweaves multimodal interaction combining
direct manipulation and natural language with flexible unit visualizations. We
employ the proposed approach in a proof-of-concept system, DataBreeze. Coupling
pen, touch, and speech-based multimodal interaction with flexible unit
visualizations, DataBreeze allows people to create and interact with both
systematically bound (e.g., scatterplots, unit column charts) and manually
customized views, enabling a novel visual data exploration experience. We
describe our design process along with DataBreeze's interface and interactions,
delineating specific aspects of the design that empower the synergistic use of
multiple modalities. We also present a preliminary user study with DataBreeze,
highlighting the data exploration patterns that participants employed. Finally,
reflecting on our design process and preliminary user study, we discuss future
research directions.
