WFS identifies items with particular secondary format characteristics; e.g. a computer file that is a serial. WFS also can be used to identify accompanying materials in a different format; e.g. a book with a CD.
| Code | Definition |
|---|---|
| a | Printed language material |
| t | Manuscript language material |
| m | Computer file |
| e | Cartographic material |
| f | Manuscript cartographic material |
| c | Printed music |
| d | Manuscript music |
| i | Nonmusical sound recording |
| j | Musical sound recording |
| s | Serial |
| t | Manuscript language material |
| g | Projected medium |
| k | Two dimensional nonprojectable graphic |
| o | Kit |
| r | Three-dimensional artifact or naturally occurring object |
| p | Mixed material |