How to define medium product

[Sharonchang]

My question is how to define medium product? For example, there are three commodity, A,B,C, A is resource, B is medium commodity, and C is final product. and AB is the process of producing B, and BC is the process of producing C. The specific problem is, there are ten regions in the model R1,R2,****and R10. It is required that only some regions produce B, and some regions produce C. So how can I define the medium commodity B?

My confusion is :

1. first I define "DEMAND" of B in each region as each regions' production volume, and I define B can be trade freely between each region to catch up the various demand of C between each region, but the optimizing result show that the "Demand" is not equal to "production", because market_B can match the balance.

2. then I change the "DEMAND" attribute to "COM_BNDPRD" and I found that the link will be broken with no B produced.

What attribute or UC should I use to solve the problem?

Thanks a lot!

Commodity  A, B,C

Process  AB: A is input, B is output

              BC: B is input, C is output

Region R1,R2,* R10