在英国使用PlantUML的公司

It is used to draw UML diagrams, using a simple and human readable text description. Be careful, because it does not prevent you from drawing inconsistent diagrams. So it's more a drawing tool than a modeling tool. It is a component that allows to quickly write Sequence diagram, Usecase diagram, Class diagram, Object diagram, Activity diagram, Component diagram, Deployment diagram, State diagram, and Timing diagram.