A graphical editor for
Situation Graph Trees


SGTEditor is a graphical editor for situation graph trees (SGTs), which allows the graphical creation, inspection and manipulation of SGTs. SGTs are graph-like structures modelling the behavior of agents. They were successfully used in terms of highlevel conceptual description of video-sequences within the (computer-) vision system XTRACK developed at the IAKS.

The basic component of SGTs is the situation scheme. A situation scheme describes the state of an agent together with the actions the agent is expected to execute whenever it is in that state. Thus, a situation scheme consists -- besides a name given to it -- of a state scheme and an action scheme.

While situation schemes describe a single point in time, they can be connected by directed edges -- called prediction edges -- to model possible sequences of situations. Each prediction edge thus represents a temporal successor-relation between situation schemes. Prediction edges from one scheme back to that scheme are allowed and are called prediction loops. Situation schemes together with prediction edges connecting them are called a situation graph. Each situation scheme in such a graph can be marked as start- or end situation. A possible sequence of situations has to start (end) in the accordingly marked situation schemes.

Each situation scheme in a graph can be connected to another situation graph by a so-called specialization edge. This means that the connected situation scheme is temporally or conceptually further particularized by the connected situation graph. The situation scheme is called more general than the situation graph and the contained situation schemes. While the connection of one situation scheme to more than one specializing graph is allowed, circles due to specialization edges are not. Therefor specialization edges build up a tree-like structure of situation schemes -- contained in situation graphs -- connected to less general situation graphs and so on.

SGTEditor was implemented in JAVA utilizing the Diagram Editor Generator DiaGen.