Not-so-free data flow in a visual data flow programming language

Three main benefits of visual dataflow programming languages (VDFLs) are the asynchronous and parallel program execution and the concrete representation of program code. In a real world, optical communication is a good example of free and parallel data flow. Therefore, we considered a VDFL as a practical tool for visualizing an optical communication flow. However, in a VDFL data flow can become synchronous and discontinuous by reasons represented in this article. The problem arises from the fact that there are no programmable control mechanisms to handle partially dependent data that appear commonly in an optical communication flow. This problem can be generalized to programming situations where a computational node of a visual dataflow program should be modified during its runtime. In this article, we introduce three solutions to the problem: dummy packets, an event switch and a dynamic computational node (DCN). Dummy packets are empty packets enabling continuous data flow of a program. The event switch is based on the use of an event handler and a property node. The DCN is also a theoretical solution as well. With the help of dynamic input and output terminals the behavior of a DCN can be modified during the runtime.