Hello everybody,

I have the following problem:

There are different products with 3 main production steps (1,2(a,b),3) and alternative resources at each production step. The number of production steps depends on the resource used at one specific production step (= variable). Meaning that, if resource x at production step 2a is used, then production step 2b becomes necessary.

I was thinking to assume that there are always 4 production steps and to include the problem by defining two modes.

Mode 1 declares the alternative resources for production steps 1,2(a,b),3 if the resource at production step 2a makes production step 2b on an extra resource necessary. And Mode 2 declares the alternative resources for production steps 1,2,3 if the production step 2b is already included in 2a and therefore 2b does not need to be carried out anymore (then there is a dummy resource for 2b with a duration of 0). The alternative resources for production step 1 and 3 are the same in both modes, only the resources for production step 2a and 2b differ.

In the first place it should be decided if Mode 1 or Mode 2 is taken. And in the second place it should be decided which alternative resources in each process step should be chosen.

Is it possible "to define an alternative in an alternative"? Or is there a better way of expressing this problem in CP?

Thanks a lot:)