> such that the expresson problem can be solved.

I'll add this paper to my reading list (because this is very much something I'm interested in), but in the meantime could you explain what you mean by "solving" the expression problem?

My understanding has been that EP is more of a lens through which to evaluate the usefulness of solutions along the objects-or-functions spectrum, rather than an actual problem to be solved in a traditional sense. Does the paper you linked design a system in which the full breadth of that spectrum is made expressible with no concessions?