This is a great site, explaining very familiar concepts of dataflow diagrams for designers firsthand. Leveling is an interesting chapter there, I’m not sure if it completely fits with the use of “Clusters” in Grasshopper but it is obvious that the complex systems should be well organized not only to be perceptually “better” ones but also to develop a way to use parts of definitions again and again in different situations.

…How do you actually DO the leveling of DFDs? The discussion thus far has been misleading in a rather subtle way: while it is true that the DFDs should be presented to a user audience in a top-down fashion, it is not necessarily true that the systems analyst should develop the DFDs in a top-down fashion. The top-down approach is intuitively very appealing: one can imagine beginning with the context diagram, and then developing Figure 0, and then methodically working down to the lower levels of detail.<ref>It’s very appealing to project managers, also. A project manager on one large project was heard saying to her project team, “I want all of you to bubble on down to the next level of detail by the end of this week!”</ref> However, we will see in Chapter 17 that there are problems with this approach; a more successful approach is to first identify the external events to which the system must respond, and to use those events to create a rough, “first-cut” DFD. In Chapter 20, we will see that this first-cut DFD may have to be partitioned upward (to create higher-level DFDs) and downward (to create lower-level DFDs). For now, it is sufficient that you simply realize that the organization and presentation of a leveled set of DFDs does not necessarily correspond to the strategy for developing those levels in the first place…

Generally, “spaghetti” Grasshopper diagrams are more appealing for architects and designers maybe because they somehow deliver the message that the designer is so “smart” that he/she can handle this complex diagram. They are even parts of the architectural and design posters purely as graphics, without carrying any clue on what is going on with the algorithm there. Anyway, maybe I should also force myself more on the use of clusters in Grasshopper.