We will perform a set of interconnection experiments to demonstrate and evaluate the bus. They will demonstrate inter-service interoperability among at least three different services, and intra-service interoperability among at least three different implementations of the same service. Some of the specific experiments we have planned are:
Interfacing of Heterogeneous Session Management Services: A global session management facility that keeps track of heterogeneous sessions defined by three different systems: XTV/Suite/Shared X.
Interfacing of Session Management and Collaborative Applications: The use of session management of a particular system (XTV/Suite/Shared X) to create sessions between users of ``foreign'' collaborative applications built using other systems. E.g: the use of XTV session management to create sessions between Suite applications and also between the collaborative VEs described below.
Interfacing of Heterogeneous Collaborative Applications: The use of different collaborative applications by different users manipulating the same artifact. E.g: the use of Michigan's multiuser DistEdit text editor and the Suite multiuser structure editor by different users editing the same document.
Position Coupled VEs: Coupling of multiple instances of a VE application, each interacting with a separate user, that allows users to see positions of the other users in their views. Motivation: position coupling of multiple instances of a flight simulation application to simulate a joint sortie and/or combat situation. Each pilot needs to know the positions of other (enemy and friendly) aircrafts.
Shared View VEs: Collaborating users see the same view. Motivation: coupling between the displays a pilot and trainer using two different instances of a flight simulator. The trainer needs to see the same view as the pilot in order to tell him what to do.
Dependent View VEs: The users have some independence in what they view but their views have dependencies. Motivation: coupling between the displays of crew members of a (single) plane using multiple instances of the flight simulation program. The gunner's view depends on the actions of the pilot, but he has some flexibility in which parts of the viewable space he actually looks at.
Users share changes to selected parts of the views. Motivation: A trainer sees only the instruments panel of the trainee's aircraft and not the whole aircraft.
Model Sharing: Users share a model but not the views. Motivation: The trainer sees a textual view of the instrument panel while the trainee sees a graphical view reflecting the actual display on the simulated aircraft.
Transaction-coupled VEs: Delayed transmission of a users actions to other instances of the VE application - the actions of the users are delayed until they commit them in a transaction. E.g: delayed transmission of the actions of users of a CAD application allowing them to collaboratively assemble a tank. Users see the results of others' actions when the latter are ``done''. Access and concurrency control ensure that users do not perform unauthorized or interfering actions.
VE-based session management: The use of a VE for starting collaborative sessions. The space of the VE is populated with icons representing applications to be included in the collaborative sessions. Users can approach an application to start a collaborative session with it. E.g: populating a VE allowing users to move from room to room of an office building. As they enter a conference room, they can start multimedia connections with others in the room, and also interact with a common set of applications.
Substituting users with agents: The use of an agent application to simulate the activities of a user. E.g: the use of an application to simulate the actions of a combatant in a flight simulator VE.
In all of these examples, we will be using existing applications to provide the VE, coupling, artifact manipulation, and agent functionality. We have chosen a large number of scenarios involving the use of VE applications since the integration of collaboration and VE is a relatively unexplored, interesting, and difficult area. We have mainly used the flight simulator example to motivate VE. In fact, we will use existing VE applications built at UNC in our experiments. In particular, we will use the state-of-the-art UNC walkthrough application, which is structured similarly to the flight simulation example used above.