The surface needs some defined condition (e.g. Isobaric) This module defines how the surface is defined. Again, much like the deformation system this does not actually implement much of the code to deform the surface to that condition; rather, it implements code to allow the prescription to be described robustly at compile time
The model must be able to deform to capture the shape induced by rotation or an external potential. Here we add the precription to descibe how we allow deformation. Note that the code to define how deformation is actually implemented is in the backend.
Note, I say this in the todo's in the files too. This system is something of a holdover from the older MeanField system which used a bespoke (per module) caching system. We may want to consider ripping this out in favor of the more general depedencies graph system now that we have it in SERiF
