# What type of scheduling problem is this?

I'm trying to develop a heuristic to solve a scheduling problem. The difficult for me is to treat the time as a variable.

There are 2 variables related to time, $$b_{ij}$$ and $$f_{ij}$$, being the time that the machine j begin and end the job $$i$$ respectively. It's used like this because the model has a demand constraint (see below), that is attended with the time that the machines do job $$i$$, and each machine has a specific capacity ($$q_j$$). There is also in the model a binary variable $$x_{ij}$$ that says if the machine $$j$$ do the job $$i$$.

$$\sum_j \bigg((f_{ij} - b_{ij}) * q_j * x_{ij}\bigg) \geq Demand_i, \forall i$$

In this problem, all the jobs needs to be processed only one time by whatever machine.

If anyone knows which kind of scheduling problem it is... It'll be a great help.