The next step in working with the Watch example is to develop a new watch. The easiest way to do this is to simply combine an existing display with an existing logical watch application. However, let us try something a little more interesting: a stopwatch-only model with four zones and two buttons. This requires the building of a real variant with a new display, as there is currently no display with four zones and two buttons.

First, open the WatchFamily diagram and create a new Display object. Enter the name for the display (‘X042’ in our example) and add four zones, (you can reuse ‘Zone1’, ‘Zone2’ and ‘Zone3’ from the existing models by selecting Add Existing... from the popup menu of UnitZones list, but you have to create a new ‘Zone4’ with Add Element...), and two buttons, (you can reuse ‘Up’ and ‘Down’ buttons from previous models). The property dialog for the display should now look like Figure 2-6. Choose OK and close the dialog.

The next component we need is the logical watch application for our stopwatch. We can reuse the existing stopwatch sub-application, but we need to repackage it before we can use it as a logical watch application. In the WatchFamily diagram, create a new LogicalWatch object and set its subgraph to be the existing ‘Stopwatch’ WatchApplication graph: Select the new LogicalWatch object, choose Manage Subgraphs... from its pop-up menu, select ‘Stopwatch’ from the Subgraph candidates list, press the right arrow button in the middle to move it to the Current subgraphs list, and close the dialog by selecting Close. The logical watch application has now been defined. Note that now we are using the Stopwatch sub-application directly from the LogicalWatch, rather than having a top-level WatchApplication state diagram in between.

To finalize our new watch model, we need to combine our new display and logical watch components into a watch model. In the WatchFamily diagram, create a new Watch relationship connecting the newly-created Display and LogicalWatch objects, and enter a name for it when prompted (‘JustStopwatch’ in our example). The WatchFamily diagram should now look like Figure 2-7.