Extending Statecharts with ad lib and multi-thread features

Statecharts is a good tool for modeling reactive systems. It models systems by means of states and transitions. Inherited from its ancestor the state diagram, the states and transitions have to be known in advance. In many reactive systems, such as Web navigation, states and transitions may not be known in advance. Multi-thread processing is also popular in dynamic reactive systems. These features are unable to be modeled by Statecharts properly. We discuss our extension of Statecharts to support these features in this paper. States and transitions are allowed to be added to the Statecharts during run time. These adding of states and transitions have to follow some rules. These rules are used to preserve the original Statecharts interpretation mechanism and avoid the unnecessary expansion. A transition is also allowed to lead to a Statechart. Together with the orthogonal construct of Statecharts, multi-thread systems can be modeled. We found these extensions fit very well in modeling dynamic reactive systems like Web navigation.