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The Decision Module in Delft-FEWS is used to implement decision logic and evaluation for iteratively evaluating barriers. With this module we can iteratively evaluate configurated decision rules. The configuration file of the Decision Module contains the definition of one or more Decision Trees. These Decision Trees defined in the Decision Module are associated with a Barrier definition which are defined by the Barriers configuration file. The Decision Module evaluation makes it possible to iterate a workflow according to the situation of the associated barriers as a result of the decision rules

Some important prerequisites:

1. The decision logic (criteria) is linked to the barrier state. Barrier states could be for example "the barrier is open", "the barrier is closed", "the barrier is halfway closed or halfway opened", "at a stage where some additional criteria need to be evaluated", etc. For each of these states, separate decision logic may be relevant and should be evaluated.
2. While evaluating the decision logic, relevant input may consist of information from both the present and future model state.

Some examples to illustrate the above:

• When the barrier is open, and when the forecast results show that water levels at location A will exceed 3 meters, the barrier should start closing when the water level at the barrier passes the 2 meter mark.
• When the barrier is closed, the barrier should be opened when the local water level gradient is negative.

1. Furthermore, the decision logic should be "scalable" (i.e. it should be easy to add additional rules). If we continue with the above example, a decision rule could also be

• When the barrier is open, and when the forecast results show that water levels at location A will exceed 3 meters, the barrier should close. If the river discharge at location C is below 6000 m3/s, the barrier should start closing when the local water level passes the 2 meter mark. If the river discharge at location C exceeds the 6000 m3/s, the barrier should start closing at slack tide. The barrier is only allowed to close when the shipping through the location B has been blocked in advance.

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