The initial blog post defined a LIS as "any computing device with a screen large enough that two or more people can comfortably use it at the same time standing (or lying, or sitting) side-by-side".
With that in mind, Elis was imagined as an operating system for such LIS devices, with the concept of a self-sufficient window that lists the device's applications and opens these applications within itself. The window would also allow resizing, flick movement, and rotation, among other features. With multiple such windows open, the operating system would provide an interface for users to work both independently, or together with one another, on a LIS device.
ProtoElis is an effort to manifest some of these ideas into a form that might be easier to develop than a full-blown operating system.