There were days when UML tools were expensive and only few commercial ones were available. But, now the market is flooded with several commercial and opensource uml tools. While choice is good, but too much choice is also bad. It has become difficult to evaluate and select the best one.
In this article I present my handpicked collection of best open source UML tools.
Papyrus is a dedicated tool for modelling within UML2. This open source tool is based on the Eclipse environment.
Taylor MDA is a specialized UML modeling tool based on Eclipse. It uses convention-based techniques to generate the maximum code from streamlined UML models. Templates are included for generating JEE applications based on JPA/EJB3 and JSF/Seam/Facelets.
The NetBeans UML plugins presently supports the following UML diagrams: Activity diagram, Class diagram, Sequence diagram, State diagram, and Use Case diagram. You can align diagrams visually in the Diagram Editor, Drag and drop roles, patterns and classes from simplified Modeling Palette and add relationships from the Context Palette.
TinyUML is a free software tool for easy and quick creation of UML 2 diagrams. It is implemented for the Java platform. At least Java SE 6 is required.