The Overture community supports the modelling method The Vienna Development Method (VDM) which is a set of modelling techniques that have a long and successful history in both research and industrial application in the development of computer-based systems.
The Overture Tool is an open-source integrated development environment (IDE) for developing and analysing VDM models. The tool suite is written entirely in Java and built on top of the Eclipse platform.
The Overture Tool project website is: http://overturetool.org