Complementary to Accessibility
  
  - Offers audio alternative to visual interaction
- Text input and output instead of speech
- Towards standards for speech commands
Complementary to Multimodality
  
  - Voice interaction is a major modality, especially when mobile
- High degree of overlap in terms of interaction management
Complementary to Device Independence
  
  - Speech recognition is becoming available on devices with differing capabilities
- Distribution of components across many devices
- Need for powerful yet simple authoring models