Exposed interfaces are instances of interfaces that are attached to an element. They represent the interaction points through which the element communicates with other elements. There are two types of exposed interfaces, ProvidedInterfaces, which are the interaces that the element realizes and offers to other elements, and RequiredInterfaces, which represent interactions that are required by the element for its internal processing. RequiredInterfaces allow you to specify all the required communications of an element without indicating what other element(s) supplies the need.
Creating Exposed Interfaces
Exposed Interfaces come in two flavors, ProvidedInterfaces and RequiredInterfaces. A ProvidedInterface on an component indicates that the component provides the functionality and/or data offered by the Interface used to define the ProvidedInterface. A RequiredInterface, on the other hand, indicates that the component needs the functionality and/or data offered by the defining Interface.
You can add an Exposed Interface to an element on any diagram. The Exposed Inteface will always be placed under the element in the project browser. Before adding a new Exposed Interface, make sure it does not already exist.
Showing All Exposed Interfaces
Before adding any new exposed interfaces, check to see that it does not already. To do so, right click on the System App and choose Embedded Elements / Embedded Elements... from the context menu. Check All at the bottom left and then close the dialog. Any exposed interfaces (embedded elements) that were not previously on the diagram should now be added. You may want to move them around for readiblility. If an interface does not have its label showing, right click it, select Appearance / Show Labels from the context menu.
Now that you are sure the System App doesn't have the exposed interface you need, you can add it by dragging the appropriate exposed interface from the toolbox onto the component.
Connecting Exposed Interfaces
Always use the Quick Link feature whenever connecting a RequiredInterface to a ProvidedInterface. If you are connecting a RequiredInterface to a ProvidedInterface with the same stereotype, you will get the (EA)<sup>2</sup> prompt in the Quick Link menu. If you don't see the (EA)<sup>2</sup> prompt, you have made a mistake and should not complete the connection. (You can choose to select a generic UML connector, but the connection will not be recognized by the EA2 reporting functions). If you draw the connector from the ProvidedInterface to the RequiredInterface, the Quick Link process will change the direction to be compliant.
Arrow Direction
There are two separate directional concepts embodied in a connector.
Source to Target
This direction is established when first drawing the connector. You draw the connector from the source to the target. As mentioned above, the quicklinker may correct this direction for you. You can change this direction later by right clicking on the connector and then choosing Advanced | Reverse Direction. It is important that the source to target direction be correct or the relationship represented by the connector may be omitted or misinterpreted in the SQL reporting.
Movement
This is distinct from the Source to Target direction and represents the direction of flow. For example, you may wish to show that data flows from a ProvidedInterface to a RequiredInterface. Since the RequiredInterface is dependent on the ProvidedInterface for the data, the connector is drawn from the RequiredInterface to the ProvidedInterface. However, this means that the arrow will point in the opposite direction of the data flow. You can change the direction of the arrow without reversing the source and target elements by double clicking on the connector, and then changing the Direction to Destination -> Source.
