Rulebased Simulation is a variation of RiverWare basic Simulation, in which an underdetermined model is provided additional information from user-specified rules that represent the operating policy of the basin. A Rulebased Simulation model does not contain enough inputs for all objects to solve. Instead, it relies on the rules to provide additional information needed to fully solve the model. Rules provide this information by setting slot values in the model. The information provided by the rules, together with the input data, results in an exactly specified model.

The rules are logical statements formulated by the modeler and written within RiverWare, in a special language which is interpreted at runtime. Thus, the rules are data which can be saved and modified without having to recompile a program.

Rulebased Simulation works by alternating between executing rules and dispatching objects on the queue. The rules set values in slots. As a result of these values, objects may have enough information to dispatch. The ensuing dispatching simulates the effects of the rules in the model.

The Rulebased Simulation controller is available in RiverWare as an alternative controller to the Simulation controller. The Rulebased Simulation controller uses the same physical process algorithms as the Simulation controller, so the same user methods and slots are available regardless of which controller is active. You do not need to modify a model built for basic Simulation to run it under the Rulebased Simulation controller, other than setting slots to “output” which will be set by the rules. Data specific to User Methods do not need to change. This allows the same model to be used for what-if scenario runs using Simulation and for policy-driven model runs with Rulebased Simulation.