On the design of a generic visual programming environment

Visual programming languages (VPLs) are usually embedded and tightly integrated within visual environments so that they are often characterised by the attributes of the environments. The creation of a VPL is, therefore, concerned with the creation of its visual programming environment (VPE). The graphical requirements of a visual programming environment include defining the visual elements of the language and the graphical relationships that must be maintained when these elements are connected together. Algorithms must be provided for graphically editing these elements while maintaining their graphical relationships. The underlying data structures are complex, containing information about visual representation, logical connectivity, domain knowledge, etc. It is difficult to parse an edited diagram with a general parsing algorithm. Any solution to solving the data structure problem tends to be so specialised that it applies only to a single visual language. The generation of every new visual language requires a re-development of the whole machinery. To avoid such re-development, we need to find a proper representation of the data structure and a generic model, which are able to decouple the components of a visual programming environment. Our approach is to view a target or domain-oriented VPE as a specific instance of a generic VPE such that the techniques applicable to the generic VPE can also apply to a target VPE and functionalities common to VPEs need not be re-developed. This paper addresses the issues in a design model that supports the development of a VPE by dividing the whole development process into several independent functional modules.