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Show CHAPTER 7 ABSTRACTION Abstraction deals with stripping away those attributes which are of least importance or interest. Abstraction allows us to easily concentrate on sections of interest by eliminating unnecessary detail. Visual clutter, a problem of too many details in too small a space, is one of the most critical problems facing visual programrmng. In the visual interactive programming environment several methods have been developed which will allow the user to control and minimize visual clutter. In addition to the well known zoom and scroll techniques, VIPER allows the user to expand, contract, hide and group multiple blocks. Techniques for creating high-level blocks are also allowed and are described in Chapter 6. Expansion may take place in a new system window (expand-in-window) or it may undo the effects of a contraction, (expand-in-place.) The user may selectively hide groups of objects or toggle the visibility of all comments or ports. Providing the user with tools to help control the display of visual information helps control visual clutter. These tools, together with the ability to create high-level blocks, manipulate the block diagram, allow specific sections of the diagram to be displayed, or hidden, at any one time. 7.1 Contract and Expand The contract command compresses a group of arbitrary blocks into a single block. When this command is invoked the user is prompted to select the elements of the contracted node. If a null group or single block is selected then the contraction |
