The figure below shows the metamodel of a hierarchical signal flow language. Notice the use of UML stereotypes for specifying how to map UML classes to GME concepts like Atom, Model or Connection. There are four aspects in the metamodeling environment altogether. In addition to the class diagram aspect that is shonw below, constraints, aspects and attributes are specified in separate aspects to manage visual clutter. The environment also supports multi-sheet diagrams through the use of proxies, that are references to UML classes in other sheets (i.e. metamodels).