Approvals
Sample model based on a real-world system that facilitates pre-approval of short sale transactions. The system
is made up of two stateful applications: one for managing the inventory for each product (InventoryApp)
and one from managing the lifecycle of batch requests from clients (LocateListApp).
LocateListApp depends on InventoryApp to execute each individual request. The dependency and mapping between
the two apps is defined in ACL.elm
Stateful Apps
Stateful apps are parameterized by 4 different types that describe how they interact with the external world
and how they manage their internal state. These are the following:
- API - Exposes functions that allow some external actor to initiate an action. Each function returns a result
that is either a failure or in case of a success an event. Internally these functions use the state to decide
if the action should fail or succeed.
- Event - Events are generated as a result of sucessful actions (either external or internal) and usually result
in internal state changes.
- RemoteState - Defines a view of the external world from the application’s perspective. The application cannot
change the external state directly. It can oly send commands to other applications to have the state changed.
- LocalState - Defines the application’s internal state. Only the application can directly modify it’s internal
state and modifications can only happen as a result of an event.