8 Advanced Uses : Composing Interactive Spatio - temporal Documents

Lately a new generation of application domains is emerging. Such applications, heavily dynamic and interactive, include interactive multimedia applications, virtual reality worlds, digital movies and 3D animations. They deal with intensive spatio-temporal dependencies between the participating objects with motion becoming a central issue. Indeed in the aforementioned application domains, much of the information conveyed and manipulated has spatial and/or temporal aspects. Synthetic worlds (like VRML worlds, digital movies, interactive multimedia scenarios etc.) can be started at any point in time, and there is a multitude of events that may occur (e.g., 3D object collisions) which may trigger other actions (e.g., change of the motion of the objects that collided) provided that some constraints hold. The session concept provides a new spatio-temporal context that has a different temporal origin and perhaps a different evolution according to the internal/external interaction that takes place. In this case the concept of scenario is an important entity representing the spatio-temporal course of the context (i.e., spatio-temporal actions possibly related) in conjunction with the occurring interaction (in terms of events) and potentially with the validity of conditions/constraints. It is therefore evident that there is a strong connection between the topics studied in the modeling of spatio-temporal information and the issues of concern in composing interactive presentations. This is the motivation for the work of this chapter; to apply knowledge earned in the spatio-temporal domain into areas not directly associated with spatio-temporal databases but still uniform with them. The result leads to the integrated study of spatio-temporal information applicable in a range of diverse uses. In the next section we relate spatio-temporal databases and interactive presentations, formally termed Interactive Spatio-Temporal Documents (ISTDs). We then present an approach for modeling the spatio-temporal components of such presentations. This focuses on the treatment of objects as integrated entities and thus apart from modeling their geometrical and positional characteristics (in an application independent format), it also demonstrates how to relate them to any non-spatial attributes. Next we analyze the method for describing the interactive behavior in these applications following the Events Conditions Actions