"or" in Constraint "or both"

[meloci01]

I want to write two constraints by using "or" :

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"There may be at most Y distribution centers or Z processing centers or both to be selected."

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Specific2..sum((i,t), y(i,t))=l=Y or sum(k, z(k))=l=Z;

But I cannot write it. Could you please help me.

[bussieck]

I recommend studying section about logical modeling in the excellent book by HP Williams (https://www.wiley.com/en-us/Model+Build ... 1118443330. Basically, make two equations, introduce binary variables that control if an equation holds and then make sure at least one of the binary variable is 1.

-Michael