service interface StateMachineNotification

The service interface StateMachineNotification provides Adaptive Applications with the state of a state machine via the readable and subscribable field CurrentState ([SWS_SM_91028], [SWS_SM_91109]). During state changes, the field signals the intermediate value "inTransition" until all actions have been executed ([SWS_SM_00616]). The interface is offered after the start of the state machine and revoked upon its termination ([SWS_SM_00618], [SWS_SM_00619]).

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Role and system context of the service interface

The service interface StateMachineNotification is provided by the State Management (SM) module of the AUTOSAR Adaptive Platform ([SWS_SM_91028]). While control applications request new state transitions via separate interfaces, StateMachineNotification interacts primarily with regular Adaptive Applications at the application layer (AUTOSAR_AP_SWS_StateManagement p. 44). The service acts as a provider (skeleton), while consuming applications are connected as consumers (proxies) via ara::com. If configured for a concrete state machine, State Management instantiates a dedicated instance of this interface ([SWS_SM_00665]). In projects where certain state machines operate purely internally and are not relevant to applications, configuration and deployment can be omitted (AUTOSAR_AP_SWS_StateManagement p. 45).

Methods, events, and fields

The interface defines no classical methods or pure events, but encapsulates the state of the monitored state machine in a central field ([SWS_SM_91109]). The field CurrentState has data type StateMachineStateNameType and is designed as read-only: It possesses a getter (HasGetter: true) and a notifier (HasNotifier: true), but has no setter (HasSetter: false) ([SWS_SM_91109]). Adaptive Applications can thus query the current value synchronously via the getter as well as subscribe to notifications in order to be informed asynchronously via ara::com upon state changes of the respective state machine ([SWS_SM_91109]).

As soon as a state transition of the state machine is started, the field CurrentState assumes the fixed value "inTransition" ([SWS_SM_00616]). This intermediate state is set independently of the triggering source—for example Execution Management, Platform Health Management, or a control application—and remains even if further transitions take place in response to error notifications (AUTOSAR_AP_SWS_StateManagement p. 67). Only when all associated actions have been processed is the value updated to the actual target state of the state machine ([SWS_SM_00617]).

Sequence diagram: Offering, querying, and notifier notifications during state transitions via StateMachineNotification. Sources: [SWS_SM_00618], [SWS_SM_91109], [SWS_SM_00616], [SWS_SM_00617]

Lifecycle, Offering, and State Dependencies

Starting a state machine is a multi-step process (AUTOSAR_AP_SWS_StateManagement p. 59). From the perspective of higher-level controllers, a state machine is considered started only once it exists and its assigned interfaces are offered (AUTOSAR_AP_SWS_StateManagement p. 59). Each configured StateMachineNotification instance is offered via ara::com as soon as the ActionListItem with command StartStateMachine has been successfully processed ([SWS_SM_00618]). This enables applications to bind to the service early on.

If a state machine is terminated or shut down, the service is revoked again: The interface is no longer available (StopOffer) from the point in time at which the corresponding termination action is processed ([SWS_SM_00619]). If state machines are controlled by a controller, the metamodel also requires that each action list references the complete set of controlled agents ([SWS_SM_CONSTR_00016]).

Error Handling and Boundary Conditions

No dedicated application-specific Application Errors (such as kOperationRejected) are defined in the interface model for StateMachineNotification, as the interface operates purely observationally and offers no modifying methods ([SWS_SM_91109]). Error handling relies on the communication mechanisms of ara::com when querying the field and on the evaluation of status "inTransition": Consumers may interpret this intermediate value as an indication of an ongoing transition or error recovery process (AUTOSAR_AP_SWS_StateManagement p. 67).