Introduction
Osyl Client needs to interact with the Sakai Server. OpenSyllabus used all the Sakai platform services we needed, in addition of our own services.
RPC
RPC (Remote Procedure Call) is the communication's workhorse of GWT.
OpenSyllabus server used GWT special RPC servlets to implement exchange of serialized Models Objects with the client application.
REST based SData
Osyl Client uses REST based calls to SData services on the Sakai server. REST (Representational State Transfer) is based on resources where each is referenced by a unique identifier, its URI (Uniform Resource Identifier). In REST, clients and servers communicate via standard HTTP and exchange representations of resources (the documents).
Thus, Sakai's SData services return JSON (JavaScript Object Notation) documents which are directly evaluated into Javascript objects by the browser.