- INSTANCE: Graph , the root , first stage edge costs , inflation parameter and probability distribution on the set of scenarios , where a scenario is a set of terminal nodes.
- SOLUTION: A subset of edges to be purchased in the first stage
- COST FUNCTION: while spans for every , where is the set of edges that have to be bought in the second stage to connect all terminal nodes.
- OBJECTIVE: Minimize.
*Approx.:*Approximable within 3.39 [101], [56].*Hardness:*NP-hard.*Comment:*In this model there are two separate stages: First stage, where and are known. In this stage one must purchase set of edges that is predicted to be useful for connecting unknown set of vertices that will be drawn from according to . Second stage, where is revealed, cost of every edge increases by a factor of and a set of edges has to be bought to connect all terminals. [49], [18].