Iteration constructs in data-flow visual programming languages

Many visual programming languages (VPLs) rely on the data-flow paradigm, pr obably because of its simple and intuitive functioning mechanism. However, there are cases where more powerful programming constructs are needed to de al with complex problems. For example, iteration is undoubtedly an importan t aspect of programming, and should allow repetitive behaviors to be specif ied in compact and easy ways. Most existing data-flow VPLs provide special constructs to implement iterations, therefore infringing the pure data-flow paradigm in favor of program simplicity, This paper has three main purpose s: (1) To provide a survey of the mechanisms used by some representative da ta-flow VPLs to carry out iterations; (2) To investigate, given a pure data -flow VPL, what should be the minimum set of characteristics which, after b eing added to the VPL, allow iterations to be implemented; and (3) To show real data-flow iteration implementations which rely on the characteristics pertaining to such a minimum set. (C) 2001 Elsevier Science Ltd. All rights reserved.