Controller

A controller is responsible for making decisions, i.e.,

• entry decisions,
• exit decisions,
• choice decisions, and
• message delivery decisions

during process execution.

A controller has to connect to an execution engine to be informed about relevant changes in the system state, i.e., about

• requests for a decision to
  • enter a node,
  • exit a node,
  • make a choice, or to
  • deliver a message,
• updates of data attribute values or global attribute values,
• sequential performers becoming busy or idle, and
• messages sent.

Moreover, by connecting to the execution engine, the engine is enabled to fetch events which are dispatched by the controller.

Greedy controller

The greedy controller implements a controller with a collection of greedy dispatchers:

• the best first entry dispatcher evaluates entry decisions for all activities and dispatches the entry decision with the best evaluation,
• best first exit dispatcher evaluates exit decisions for all activities and dispatches the exit decision with the best evaluation,
• best matching message delivery dispatcher evaluates message delivery decisions for all sent messages and potential recipients and dispatches the message delivery decision with the best evaluation.
• the best enumerated choice dispatcher evaluates all choices that can be enumerated. In case, of numeric choices lower bound and upper bound as well a discretize condition must be provided, e.g. lb <= choice <= ub, 5 divides choice where lb and ub may be arbitrary expressions and choice is the attribute name for which the choice is to be made. The discretize condition accepts a numeric value or an expression. If no discretize condition is provided only minimum and maximum values are considered.

Among all decisions dispatched by any of the greedy dispatchers, the greedy controller selects the decision with the overall best evaluation.

All evaluations are conducted by an evaluator.

Evaluator

The evaluator is responsible for determining whether a decision can be taken without violating any restrictions and to quantify the value of taking the decision.

Local evaluator

The Local evaluator makes local observations to evaluate a decision.

Guided evaluator

The Guided evaluator makes local observations and includes guidance provided with the model to evaluate a decision.