The json viewer provides a RESTful interface to the domain object model, running over the HTTP protocol, and implemented as a webapp (servlet).
Each domain object (or part of object) is exposed as a RESTful resource, in a JSON representation.
The viewer is an implementation of the Restful Objects specification, intended to allow other server-side frameworks to be implemented to support the same protocol.
See this module's applib, viewer and user guide for more information.