A metamodel for the notation of graphical modeling languages

In order to define a graphical modeling language, it is necessary to define the graphical notation of the language in the process of metamodeling. So the defining of the notation has become one of the essential functions in meta-modeling tools. This paper proposed the Notation Definition Metamodel (NDM) for metamodeling tools. NDM is used to define the graphical notation. It consists of three parts: basic figures and layouts, location relations and syntax bridges. NDM has been implemented in PKU Meta- Model Tool (PkuMMT). The paper made a case study to illustrate the feasibility of NDM. Besides, a comparison between PKU MMT and some metamodeling tools is presented to show the capability and advantages of NDM.