[DISCUSS] Rearchitecture & roadmap change proposal

Hello devs, Spent some time did some small-group discussion for the Submarine architecture, use cases, and roadmaps. (Thanks for all the inputs from Yanbo, Xun, Wei-Chiu, Zhankun and many others). Basically, we want to better align the goal of UI and backend development, target to create a unique

Re: [DISCUSS] Rearchitecture & roadmap change proposal

After discussed with the community members, I updated the design doc into 3 pieces: 1) Removed lots of duplicated contents and detailed implementations from the architecture doc. 2) Added imple