Graphics Programs Reference
In-Depth Information
on a specific object or set of objects, or generically
in the collaborative shared environment. From
a WebTalk04 point of view, actions are single
components that are invoked in a particular instant
by someone (typically an avatar) or something
(typically an object). So actions are modules that
we can configure in order to obtain the dynamic
reaction we want.
Below are listened the most important action
modules that our architecture supports (more
detailed view in next sections):
to determine the operations that may be carried
out on a given object by a given user.
In a CVE we need a set of rules or access
patterns, which determine whether a user, group
of users, or user playing a particular role, can
perform a specified action.
As our main concern is to control and drive col-
laboration through appropriate policy of resource
and interaction control, we can divide, according
to the resource access in Virtual Environments,
systems in two main types:
DragObject : Allows dragging of the shared object
in the 3D world. This is a 3D drag that allows
movement and rotation of the shared object.
ChangeColor or ChangeTexture : Changes the
colour or the texture of the specified shared object.
Showtooltip : Shows a label near the object in the
3D world.
StarTrek : Moves the avatar into a specific part.
goToUrl : Opens a new browser window on a
specific page. This is used to open boards, for
example.
StartAnimation : This action is used to start a shared
object's embedded animation.
1. Class-based access . This is a programmatic
and developer issue and is concerned above
all with the integrity and the structure of the
underlying programs/objects that form the
VE.
2. Object-based access . Refers to the relation-
ship between the affordances of objects and
their users as, for example, the availability
of an object to be “moved” or “owned” in
some way. This is the type of access paradigm
on which we founded the WT04 interaction
model and its runtime engine.
In our model, interaction is achieved and
controlled through a mechanism based on three
main concepts using the paradigm of Event Con-
ditioned Actions :
Access Control and Behaviors
In WebTalk04 the collaboration issues between
user-to-user or user-to-object is intrinsically
correlated to the above-mentioned interactions'
primitives as virtual actions supported by the
environment, as well as its capability to control
and drive collaboration in a specific and well-
defined direction.
In this sense issues such as object ownership
and resource management have a great importance
on the whole architecture.
Access control is a familiar concept in such
fields as operating systems and Computer Sup-
ported Collaborative Workgroups, or CSCW (Pet-
tifer & Marsh, 2001). The term ' access model '
refers to a set of mechanisms used by a system
1. Entity : a general resource within the sys-
tem. An entity may be a shared object with
a graphical representation, or an abstract
concept with no visible representation as, for
example, a server side remote shared object
mapping a certain property of the system.
Such entities provide a set of properties
representing in some way the inner state of
the entity and an amount of listener which
the entity is registered to that allow it to react
to events and perform one or more actions.
In this view users and their own avatars can
be considered a particular kind of entity.
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