A visual language and environment for specifying user interface event handling in design tools

End users often need the ability to tailor diagramming-based design tools and to specify dynamic interactive behaviours of graphical user interfaces. However most want to avoid having to use textual scripting languages or programming language approaches directly. We describe a new visual language for user interface event handling specification targeted at end users. Our visual language provides end users with abstract ways to express both simple and complex event handling mechanisms via visual specifications. These specifications incorporate event filtering, tool state querying and action invocation. We describe our language, its incorporation into a meta-tool for building visual design environments, examples of its use and results of evaluations of its effectiveness.