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Lesson 7 Partition dependencies
Objective Identify and define dependencies between partitions.

Dependencies and associations

Dependencies describe a relationship between partitions. You can figure out where the dependencies are by evaluating the associations. One class is associated with another class because there is some form of communication between them. Objects of one class might query the other class for information. For example, the ShowSeat might ask the Seat for its location details to print out the Ticket.

Dependencies and interactions

One way to find the direction of the dependency is to look for the direction of the communication between the objects. In the sequence and collaboration diagrams, you documented the way that objects talked to one another.
Click the View Image link to examine dependencies and interactions. Find the interaction diagrams where the two types of objects communicate. Find out whether the event arrows all go one direction or whether they go both directions. The direction(s) of the event arrows will tell you the direction of the dependency.
Dependency Associations

Functional dependencies

A dependency may also exist between a function and a class or object. For example, the object model tells you that Shows must be part of an Event (composition). In order to create a Show object you should invoke the Event object, ask it to create a new Show, and add the new Show object to its composition. The Show Management function (use case) initiates the addition, cancellation, and rescheduling of Shows. But Show Management depends on the Event object from Event Management to do the actual work.

Time dependency

Yet another way to identify dependencies is to determine which object has to exist first. For example, in the Pricing subsystem there is no object interaction that would tell you explicitly in which direction to draw the dependency. Both the show and the pricing plan objects have to exist before the Show pricing subsystem can do its job.
Time dependency
Time dependency

Partition Dependencies - Exercise

Click the Exercise link below to work on the course project. In this exercise you will practice determining the dependencies between domain partitions.
Partition Dependencies - Exercise