Source code of a graphical designer application may be generated from a definition of graphical elements that can be employed to develop graphical models using the graphical designer application, a definition of one or more object types that can be represented in graphical models developed using the graphical designer application, and a definition of a mapping between the one or more object types and the graphical elements. One or more of these definitions may be stored within a file formatted in accordance with a markup language such as SGML or XML. The graphical designer application may be customized and extended by modifying one or more of the definitions and regenerating the source code and/or by modifying the source code itself. One or more of the definitions may be generated based on a graphical designer template corresponding to a particular model domain.