Fedora Services

The only means of direct access to an object’s datastreams are through its disseminators. Each dissemination request then will require a communication or access protocol to convey the specified action and an application on the remote or local host to actually execute the action. For example, if the dissemination request is to retrieve a RealVideo stream then the action will use HTTP to communicate the request, but a RealVideo streaming server must exist on the remote/local host to serve up that video stream. We envision these application services as being physically separate from the repository (or at least accessible as if they are) and connected through the communication protocols as pictured in the Fedora Services Model.

A comprehensive digital library system would need to include a suite of “services” that provided video streaming , audio streaming,  image rendering, GIS rendering, xml rendering, numerical data analysis/statistics, SQL database services, and indexing and search services. The addition of a new disseminator to an object assumes that the behavior provided by the disseminator has a corresponding service either on the repository system or a remote host that provides the service to implement that behavior.

Currently all of the services implemented in the prototype use HTTP as the communication protocol, but we hope to experiment with adding new protocols like Z39.50 in the near future.