FLOW is a flowchart graph library. Unlike other graphing libraries, this one focuses on nodes in a graph having distinct ports through which connections to other nodes are formed. This helps in many concrete scenarios where it is important to distinguish not only which nodes are connected, but also how they are connected to each other.

Particularly, a lot of data flow and exchange problems can be reduced to such a flowchart. For example, an audio processing library may present its pipeline as a flowchart of segments that communicate with each other through audio sample buffers. Flow gives a convenient view onto this kind of problem, and even allows the generic visualisation of graphs in this format.