Graphical modelling using contextually implied functions
Carlo J. Evangelisti · The Computer Journal · 1971
Many physical problems can be represented by block diagrams or, more generally, by topological graphs. The nodes or blocks correspond to objects with specified attributes. The edges or lines between nodes represent relations between the objects and may also have attributes. A modelling (drawing) system is described that allows for block diagrams to be entered into a computer via a graphical console such as the IBM 2250. The techniques involved do not require a user to explicitly tell the machine which drawing function he wants executed; the operands he chooses determine the function. Thus, the system eliminates the need for function keys or light keys while the model is being created and permits the user to operate solely with a light pen. Keys are used only for functions that are secondary to the creation of the model, such as the filing function for example. A set of functions useful for creating block diagrams is presented. These functions provide the ability to copy blocks, draw lines between blocks, and erase lines or blocks. Functions pertaining to the attributes provide the ability to specify attributes, change attributes, and associate attributes with lines or blocks. Finally, a file structure is described and filing and retrieval functions are presented.