seqdiagram-ed is a tool to produce UML 2.0 Sequence Diagrams. It uses Javascript, HTML and XSLT and runs completely in the browser.

have proposed in [9] the ACES design flow that is a complete design flow that starts from the UML level. ACES design flow grabs the system specifications through the class, state machine, activity, ...

Workflow/State Machine Engine written in modern C++. Offers a comprehensive DSL (Domain Specific Language) for UML state machines. Comes with a runtime to run, trace and visualize your state machines.