A few years ago there was an MIT research project about a visual programming language where the program was represented as directed graphs. Does anyone know of

A few years ago there was an MIT research project about a visual programming language where the program was represented as directed graphs. Does anyone know of such an MIT project from the early 2000s? There were a few things that set this programming language apart from most of visual programming environments. First of all it was a proper programming language and not a toy project. The graph structure visualized recursion and re-use of variables very well. The code could be evaluated and edited at the same time by collapsing parts of the graph. You could collapse every iteration of recursion in the graph. The most striking difference with normal programming languages was that all names were purely optional documentation. Too bad I can't remember the name of this project. I remember seeing a presentation video of this project which got me really excited. It was a language by computer scientists, for computer scientists and not something done for kids or designers to get their first baby steps in programming. Out of the ones on the list, AppInventor/Blockly/Scratch is definitely my favorite. There are different puzzle pieces for different syntactic structures, statements and expressions in particular. The puzzle pieces are colored by the type of the expression they represent. This makes it easy and obvious which piece fits where.