![](bg3.png)
an information space with this structure is called ’in-
formation graph’ in the following.
Many restrictions of classic whiteboards are om-
mited with the generalization to an information graph
structure:
• Workspace: A virtual workspace needs not to be
bounded. There are no restrictions to the level of
detail a workspace can have.
• Objects: Information objects can be of any dig-
itally representable form and are not restricted to
text and graphic types. Objects can easily be ma-
nipulated, moved and removed.
• Links: Links are not restricted to symbols. They
can be moved easily with the linked objects.
Beside text and graphic objects, common object
types in virtual environments are multimedia data,
documents, and internal/external links.
While the information space model is synchronized
between all users, the visualization is not. This allows
a much more flexible handling and dynamic changes
between close and loose collaboration. While the lo-
cal workspace is bounded, the global workspace (i.e.
the information space) is not. Users also can have
different views on the (global) workspace. A differ-
entiation between the global coordinate system of the
information space and the local coordinate system of
the local workspace is required. The visualization
therefore is a projection from the information space to
the local workspace. As part of the global workspace,
the information objects are also being projected. This
allows assigning multiple representations for a sin-
gle object type. Two possible representations are a
workspace representation, like an icon or label, and a
detail representation, which enables access to all ob-
ject information. The visualization of links between
objects strongly depends on form and complexity of
the chosen link model.
For the interaction with the information space, a
minimal set of object operations has to be realized:
creation, manipulation, movement, and deletion. In-
teraction between users takes place through interac-
tion with information space objects, so a small exten-
sion to the set of object operations is required: selec-
tion and deselection. An object can only be selected if
it is not selected by another user. In addition to the ob-
ject operations, linking of objects has to be provided
as inter-object operation.
’Workspace Awareness’ is part of visualization
and interation. It comprises all mechanisms which
support the awareness among the users interacting in
the (shared) information space. For visual aware-
ness mechanisms, an additional information channel
is needed, which allows identifying the interacting
users easily. An appropriate channel is available in
form of coloring. Because the workspace visual-
ization realizes loose WYSIWIS
3
, awareness mech-
anisms for loose and close collaboration are required.
In a loose collaboration, a user must be informed
where the other users are acting. In close collabo-
ration, a user must be informed about what the others
are doing.
4 IMPLEMENTATION AND
EVALUATION
The so-called Synchronous Learning Environment
(SLE) is a sample implementation of the concept in-
troduced in section 3. It is divided into four separable
modules: data management, user management, com-
munication, and workspace. The modularization has
several advantages: It allows to enhance or to replace
single modules without affecting the others as long as
the interface is maintained. For example, the commu-
nication module can either be a voice or a video chat
depending on user preferences, bandwidth or hard-
ware requirements.
The user management module provides user iden-
tification and user session handling. The data man-
agement module is informed about information space
changes and maintains a persistent representation. In
the current version, the communication module real-
izes a simple voice chat. Central element of the SLE
is the workspace module. It is built as client-server
achitecture. The server provides a reference model of
the information graph. The clients share the global
workspace and are responsible for projection, visual-
ization and interaction.
The considerations in section 3 leave room for
models of different complexity. The currently imple-
mented information space model is a minimal model
according to the findings. The information space has
the form of an information graph (two-dimensional),
is unbounded and provides the functionality of plac-
ing information objects in an origin-centered, real-
valued coordinate system.
Implemented information object types are: Label,
Image, Binary, URL, and Graphlink. Label is a simple
single-line text object. Image is a container for JPG,
PNG, and GIF graphics. A Binary object corresponds
to the ’universal’ object and handles arbitrary binary
files. External and internal links are realized with the
URL and Graphlink object types. Links are realized
as simple non-directed 1:1 mappings.
3
What You See Is What I See.
DESIGN OF A SYNCHRONOUS COLLABORATIVE LEARNING ENVIRONMENT
425