Here is a draft of requirements (working in progress).

https://docs.google.com/document/d/109pxj-90Ly58ma8CoeRKcMoPWBD0G911E53MeK2zhhA/edit?usp=sharing

Currently, it listed some of the working scenarios for the runtime, and more sections should be added.

Once we have agreement on the requirement, the doc should be put into repo as a markdown doc.