Good question - Currently our approach to semantic layer creation is based on source data, interaction with the agent, and publishing workflows. We recompute the semantic layer every time a user takes an action that fits in those categories. We also plan to give the user the ability to be able to edit the semantic layer. Wrt to synced or uploaded source data, we plan to alert the users, when a change is detected. Additionally, we have been contemplating version controlled semantic layers to be able to provide the user the control as well, which would help in the scenario you have mentioned