An Organizational Tool

In addition to the modeling diagrams we have identified so far, the UML also provides packages. Packages are not a modeling tool. Packages are an organizational tool.
Packages allow you to organize or group the UML modeling diagrams into logical units.
For example, one package might contain the models that describe the user interface (class diagrams, collaboration diagrams, components, and use cases) while another contains the models that describe the back end server. The grouping is entirely up to you. The groupings should facilitate inter-team and intra-team communication and support of the application development process.

The package concept is covered in the last module along with component and deployment diagrams.
I have included packages because they often map to the directory structures that are employed when organizing the contents of a project.
Even though packages identify logical groupings, they are employed as physical repositories of your work.
For now, simply recognize that the UML provides not only a complete set of tools for the modeling process but also a solid general purpose tool for organizing your work. The next lesson concludes this module by discussing standardization.