File Based Streams

AFF4 uses FileBackedObject to store data backed by a file on the filesystem. Like all AFF4 objects, the FileBackedObject has a URN which uses the file scheme to denote the path to the file.

Strictly the file URN is not globally unique, and therefore not suitable as an AFF4 URN. For this reason it is not usually stored permanently in volumes, but it is usually inferred.

The AFF4 library will not usually create a new file or overwrite an existing file. Unless the attribute http://aff4.org/VolatileSchema#writable is set to “truncate” or “append”. This mechanism requires users of the library to specify in advance which files will be created or overwritten by setting this attribute.

Information Model

Predicate	Description
http://aff4.org/VolatileSchema#writable	This attribute signals that the file object should be writable. It can take on the value “truncate” or “append”. Note that this predicate is volatile which means it is never written into an AFF4 container.