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doc_event_using_useValuesFromTriggerTime Class Reference

Detailed Description

The optional Delay on Event means there are two times to consider when computing the results of an event: the time at which the event is triggered, and the time at which assignments are executed. It is also possible to distinguish between the time at which the EventAssignment's expression is calculated, and the time at which the assignment is made: the expression could be evaluated at the same time the assignments are performed, i.e., when the event is executed, but it could also be defined to be evaluated at the time the event is triggered.

In SBML Level 2 versions prior to Version 4, the semantics of Event time delays were defined such that the expressions in the event's assignments were always evaluated at the time the event was triggered. This definition made it difficult to define an event whose assignment formulas were meant to be evaluated at the time the event was executed (i.e., after the time period defined by the value of the Delay element). In SBML Level 2 Version 4, the attribute "useValuesFromTriggerTime" on Event allows a model to indicate the time at which the event's assignments are intended to be evaluated. In SBML Level 2, the attribute has a default value of true, which corresponds to the interpretation of event assignments prior to Version 4: the values of the assignment formulas are computed at the moment the event is triggered, not after the delay. If "useValuesFromTriggerTime"=false, it means that the formulas in the event's assignments are to be computed after the delay, at the time the event is executed. In SBML Level 3, the attribute is mandatory, not optional, and all events must specify a value for it.