Components of Unified Service Desk
Unified Service Desk provides an object-oriented kind of configuration and development experience through its hosted control implementation where the hosted control is equivalent to the object in a typical object-oriented development, and is used throughout Unified Service Desk to provide its loose coupling of components. More information: Hosted Controls
The following diagram depicts the object-oriented development concepts and the Unified Service Desk equivalents.
However, there are some important differences between Unified Service Desk implementations and the typical object-oriented design:
Replacement parameters, unlike properties, are stored external to the object (hosted control in the case of Unified Service Desk) itself. This has a distinct advantage in Unified Service Desk that the properties persist longer than the life of the object, thereby allowing action calls to access the properties for use in parameters or logic long after the hosted control that exposed the parameter has been closed. More information: Replacement parameters
UII actions are equivalent to the method declaration. The action must first be defined by the underlying object that implements the action, and then it can be declared in the Common Data Service platform as a usable action. Action calls in Unified Service Desk are essentially calls to these UII actions and typically use replacement parameters as the parameters to the specific UII actions. So while UII actions represent the declaration of the action that can be executed, the action calls represent the actual call to the action. More information: UII actions, Action calls
Events in Unified Service Desk make one or more action calls, which internally call UII actions on other objects. More information: Events