You can partition your model into units down to the class level. Creating units simplifies collaboration in team environments. With this feature, you have explicit control over file names and modification rights, and you can check unit files in and out of a configuration management system.
The project and all packages are always units. The following table lists other project elements that can be units.
| Element | File Extension | Unit by Default? |
|---|---|---|
| Actors | .cls | No |
| Components | .cmp | Yes |
| Packages | .sbs | Yes |
| Classes | .cls | No |
| Implicit objects (parts) | .cls | No |
| Files | .cls | No |
| Diagrams (except statecharts and activity diagrams) | Block definition diagrams (*.omd) | No |
| Component diagrams (*.ctd) | No | |
| Collaboration diagrams (*.clb) | No | |
| Deployment diagrams (*.dpd) | No | |
| Internal block diagrams | No | |
| Object model diagrams (*.omd) | No | |
| Sequence diagrams (*.msc) | No | |
| Structure diagrams (*.std) | No | |
| Use case diagrams (*.ucd) | No |