SE450: Packages: Package Diagrams [8/47]

A top-level package diagram typically shows all of the packages in a system. Sometimes it also includes the public classes/interfaces within each package (usually by name only--no fields or methods listed). You can then show the dependencies between these public portions of the packages.

Here is a small example:

    +---+                       +---+              
    | x |                       | y |              
    +---+-------------+         +---+-------------+
    |                 |         |                 |
    | +-------------+ |         | +-------------+ |
    | |<<interface>>|<----+-------|Main         | |
    | |      I      | |   |     | +-------------+ |
    | +-------------+ |   |     |                 |
    |                 |   |     +-----------------+
    |  +----------+   |   |
    |  |<<static>>|<------+
    |  | IFactory |   |
    |  +----------+   |
    |                 |
    +-----------------+

There are two packages, x and y. x has two public classes: I is an interface and IFactory has only static methods. y has one public class: Main. y.Main depends on x.I and x.IFactory.

Note that the diagram does not show "intra-package" dependencies, only "inter-package" dependencies; that is, we do not show dependencies within a package, but only between packages.

Here is a more abstract version:

    +---+             +---+    
    | x |             | y |    
    +---+---+         +---+---+
    |       |         |       |
    |       |<--------|       |
    |       |         |       |
    +-------+         +-------+

A system document would usually also have a class diagram for each package, showing in more detail how the package is implemented.