Design Workflow:
- spend little time making a couple design decisions -- lots of handwaving and "we'll figure it out"
- bind these decisions, then write a tiny app to see what it looks like. What are the technical consequences? What are the business consequences (including risks)? How does this affect development?
- repeat 2-4x. The goal is to maximize speed of feedback, at the cost of minimal scope and low quality. That's fine.
- iterate more, expanding the scope and quality as needed
- you're done!
Use high-level diagrams to help focus the effort. This dramatically helps discussions with stakeholders and developers.
Source: writing a book on feedback loops