UTP12 — Align test-related actions for Interactions with UML 2.4

In the current UTP specification, the different test actions (StartTimerAction, ValidationAction, etc.) are indirectly bound to a lifeline by being referenced from an ActionExecutionSpecification that covers a lifeline, representing a structured classifier with <<TestComponent>> stereotype applied. This was necessary because there was no adequate meta model element in Interactions for placing a single action onto a lifeline. With UML 2.4, the meta model of Interactions have been reworked significantly in the way that the meta model element OccurrenceSpecification became a concrete class, specializing InteractionFragment. An OccurrenceSpecification has a reference to exactly one lifeline it covers. This the precise redefinition of test actions for Interactions, using the new UML 2.4 semantics.

Therefore, each test action (StartTimerAction, StopTimerAction, ValidationAction, etc.) shall extend UML::OccurrenceSpecification directly. Since OccurrenceSpecifications do not have a notation a priori, each test action has to define a dedicated notation (for some actions, there is already a notation defined, e.g. TimeOutMessage). This makes the actions easily and freely positionable on the lifelines. By doing so, the applicability of UTP would be significantly simplified. Besides, the memory footprint in the background would be extremly decreased, due to the fact that the event would be bound directly to the OccurrenceSpecification instead of creating a lot of elements (ActionExecutionSpecification, Action, Event, Input/OutputPins...)