Reactive Blocks[1] is a visual model-driven development environment based on Activity Diagrams supporting formal model analysis, automated code generation, hierarchical modelling, and an extensive library of ready-to-use components for the Java platform.
The existing library can be extended by user-implemented custom blocks which can include the full abilities of the Java platform.
Each block has an extended interface description in the form of input and output pins and a contract.
Reactive Blocks uses the graphical model together with the information from the contracts to formally analyse the application to discover common problems such as deadlocks or incorrect terminations.
The development environment offers a step-by-step animation of the chain of state transitions leading up to the problem.