Task: Define Observation Model
The model of the observer, the controller, and the relation to the agents has to be adapted to the system.
Relationships
InputsMandatory: Optional: External:
  • None
Outputs
Main Description

The definition of the Observation Model is a first crucial step before the transformation process can begin. It defines the monitoring infrastructure and the interactions between it and the system. The transformation process will create instances of the classes defined in the model. If an exisitng observation model is used, this task defines the relationship between the observation model and the agent and system architecture.

Steps
Identify and define relevant classes
When sticking to the Observer/Controller Architecture, at least classes for observers and controllers have to be defined. It is often helpful to also specify an agent model that holds the current agent state and classes for different types of constraints. Existing elements from the agent or the system architecture can be re-used for this purpose or new ones can be introduced.
Define interaction between observer and agents
A crucial aspect of the observation model is the way the observer gathers data from the agents. It is possible that the observer can directly access the state data of the agents, that the agents communicate this information, or that the observer solely relies on external observation.
Define interaction between observer and controller
Define the way the observer informs the controller of constraint violations and the controller informs the observer of a finished reconfiguration. If necessary, the interaction between the controller and the agents should also be specified here.
Define relevant associations and fields of the classes in the observation model
Depending on the way information is exchanged between observers and agents and how the observers and the controllers interact, as well as the way state information about the agents is stored, associations between the classes have to be introduced and fields have to be added.
Specify behaviour of relevant methods
Both the observer and the constraint classes contain methods that implement crucial system behaviour. The method that checks whether a constraint holds is one example for this. As these methods will have to be transformed into code later on, these methods should be specified, e.g., with activity charts to unambiguously define the dynamic behaviour. For the example mentioned, the method should contain a placeholder for the concrete constraint that will later be checked by a specialisation of the class, realising a variant of the Template Method pattern.
Properties
Multiple Occurrences
Event Driven
Ongoing
OptionalYes
Planned
Repeatable
Key Considerations
Use sequence or interaction diagrams to specify the interactions between the classes in the observation model.