Fundamentals of UML Diagrams
A diagram is the graphical presentation of a set of elements. UML has a lot of different diagrams. Make sure you can differentiate between different diagrams. Previous sections described UML diagrams; this section elaborates on them using examples.
Using the <> relationship
Package Diagrams
Any non-trial system needs to be divided up in smaller, easier to understand "chunks". A package is basically a logical container into which related elements can be placed, "like a folder or directory in an operating system". We can display groups of packages and relationships between them on the UML package diagram.
Packages does not show actually what is inside the package, it provides a very "high-level" view of the system. Some case tools allow the user to double-click on the package icon in order to open-up the package and explore the contents. The common use
of a package is to group related classes together, sometimes group related use cases.
Packages can be used to:
- Group large systems into easier to manage subsystems
- Allow parallel iterative development
Package diagram in Figure 2.13 shows three UML packages representing a "three-tier model"
Figure 2.13: Example of a Package Diagram