| Name | Kind | Description |
| Unknown | class | placeholder for unknown or unavailable media source |
| unknown | artifact | placeholder for unknown or unavailable media source |
| usage | use case view | |
| use "default" object | use case | |
| useFile | operation | Announces that the application intends to use this file with mode (READ|WRITE|READWRITE) |
| User | class | |
| useTemporaryStorage | operation | Provides a pool for interminate frames |