Collaborative Learning through Flexible Web CVE - Teaching through Multi-User Virtual Environments - page 478

virtual world has to be rendered, as well as in
which way the action can take place and evolve.
WT04 authoring environment where the de-
signer defines and fine tunes the world structure
and the specific behaviors attached to each user
or interactive objects.
As shown in Figure 3, we devised our logical
architecture as a 3-tier system, detailed as follows:

environment (coded in Macromedia Director and
Flash technology) that interprets the declarations
and provides to instance the right components
taken from a library (from one hand it instances
the right 3D models in the world, on the other it
sets up the collaboration's rule that will govern
the shared experience).

Design Consideration

1. Scene graph and behavior schema : coded
through XML-Schema it represents the
structure of a valid WT04 compliant XML-
instance, where it has defined the elements
composing XML-instances, hierarchical
rules between elements and supported data
types.
2. Scene graph and behavior instance pro-
totype : a XML document representing the
skeleton of a collaborative session where
designer had already fixed geometries form-
ing the virtual environment as well as the
main users' interaction rules.
3. Scene graph and behavior instance : the
final and XML instance completed with all
information and contents depending on the
specific context (specific users involved,
specific target of the experience, particular
topics given).

One of the essential goals of CVE is to provide
the capability of combining multi-participants and
the information that they access and manipulate
in a single place. We focused our designing con-
siderations and research work on the following
components of a CVE system:

1. Virtual world representation
2. Avatars
3. Shared objects
4. Virtual actions
5. Access control and behaviors
6. Collaborative metaphors
7. Network communications

To implement an effective CVE system, we
have to take care of the previous components, each
playing a basic and important role in the overall
system, then our declarative description we have
to formally describe all these issues.
First of all, a CVE system has to provide a
shared environment for users to cooperate with

When an XML instance is generated, system
is ready to start a collaborative session. The XML
file is sent (at run time) to the clients' runtime

Figure 3. WebTalk04 declarative system levels