This dissertation reports on the development of a prototype programming environment for a graphical programming language to support a data-driven style of computation. Emphasis is on the need for tools to assist in the development of nontrivial graphical programs. Within the scope of programming languages there has been a lot of criticism that the current languages force an unnatural form for solutions, which is difficult to read, and even harder to verify, debug, maintain, and modify. One of the major "culprits" for all of these problems is felt to be side effects; thus there have been several proposals to create functional languages. One class of functional solutions which has received an increasing amount of interest is the area of data ...