Hello everyone,

I am trying to implement a supply and demand model in AIMMS. This is the first time using it for me and I'm having some issues.

The case is as follows: There are Printer companies that supply books to Retailers. These Printers can send the books directly to retailers, or through crossdocks to be consolidated.

I have modelled the set of Printers with index P, the set of Crossdocks with index C and the set of retailers with index R. The case asks for a set of locations as the union of these three sets L = P ∪ C ∪ R. I am not sure how to model this union of sets and can't seem to find any info on this. Does anyone know how to do this?

Not sure if it matters, but the amount of Printers, Crossdocks and Retailers should be variable and dependent on an Excel input file.

Thanks!

**Best answer by Gertjan**