Implementing a visual programming language (VPL) is much harder than implementing a textual programming language (Myers 1990). VPLs are usually embedded and tightly integrated within visual environments. Consequently, they are often characterized by the attributes of the environments (Goldberg et al. 1994). The VPL implementation involves the implementation of a whole programming environment with a user interface which supports developing programs using a visual language. Notice that VPL interfaces are not the same as graphical user interfaces (GUIs) nor are they just for visualization. Traditional GUI development toolkits are inadequate for the creation of VPLs because they do not support syntactic and semantic specifications of visual programming. The graphical user interface of a visual language relates to the language’s syntax and semantics. The interaction (dialogue) between the interface, the syntax and the semantics must be maintained. Implementing a VPL interface and its support for syntactic and semantic specifications of visual programming suffers from a problem common to all large, complex software systems, i.e. the generation is difficult and time consuming. The remaining part of this section will address the typical problems of implementing VPLs.
KeywordsVisual Object Graph Node Graph Grammar Visual Language Super Node
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