Fundamentals of UML Diagrams

3.5. Package Diagrams

Any non-trial system need 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 then 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: 

Package diagram in Figure 2.13 shows three UML packages representing a "three-tier model"

Figure 2.13: Example of a Package Diagram