The Web Modeling Project is similar to the GMF runtime project or the Graphiti project, but for the web world. It is used to build GenMyModel.
The Web Modeling Project goal is to provide as many online diagramming and modeling features as possible "out of box".
The framework already implements some diagramming behaviors you just have to choose to implement your own online diagramming editor.
It provides some abstract classes you have to inherit to get your own graphical widgets. Both diagramming widgets and modeling widget (treeview, property panels) are supported.
The diagram elements design is provided using CSS.
The Web Modeling Project framework supports nodes, links, and node hierarchy (e.g. packages).