FEDORA
Flexible Extensible Digital Object Repository Architecture is open source digital object repository software originally developed by Cornell University and prototyped by the University of Virginia Library. Hundreds of organizations and institutions now use Fedora as the foundation of digital library structures for storing, managing, and accessing all types of digital content.
One of the attractions of Fedora is its digital object model. For digital objects, content can be of any type (documents, images, datasets, etc.) and more than one content item can be part of an object. Also, content can be stored in the Fedora repository itself, or it can be kept external to the repository and represented by a URL.
Digital Object
The digital object is mainly a collection of data streams, the electronic signals used to represent information. As seen in the screenshot at right, an object can have data streams containing metadata of multiple types, data about system policies, object and other data stream relationship definitions, and a digital item, here an image formatted as a JPEG. It also contains a unique, persistent identifier* that will follow the object throughout its lifespan.
*PID
A Persistent IDentifier is a name of a digital object that eliminates confusion with other objects and ensures long-term access to the object and its parts. Especially in Fedora, a PID will always be attached to one and only one particular digital entity, and it will always tell you where to find that digital entity (even if it moves). A PID might look something like uva:peekskill89.