[imtringued]

Symbolic math equations isn't a low level solver API. That's the high level interface. A low level interface expects you to provide the optimization problems as raw matrices.

What you're talking about is known as a problem reduction.

[ge0ffrey]

I would argue that inputting a loadBalance(sum(shift.duration)) function per employee is a higher level abstraction than inputting a quadratic math equation to accomplish the same thing.

Think Java/C++/Python vs Assembly.

Ironically, talking about problem reduction... most math equation based solver can't scale quadratic equations, so users "relax" the business constraints (to the point that projects fail in production).