Develop a Formal Semantics for Mosaic Selections

[domoritz]

Some aspects of our selection abstraction may be the result of ad hoc design. The goal of this project would be to develop a full formal semantics for Mosaic’s selection abstraction, potentially updating/improving the current implementation in response. The initial focus should be on the semantics of a single selection shared across one or more clients. As a stretch goal, possible extensions might include selection composition to build up more complex selections.