[zozbot234]

UML is non-rigorous and has a whole lot of pointless incidental complexity. Intuitive representations of parallelism are fairly natural in data flow, but that is precisely dual to flowcharts; you can not represent both on the same 2D diagram without some very precise rules about what portions of the diagram are intended to represent each. Proof nets give you something not unlike this.

[AnimalMuppet]

Oh, I never said UML was ideal. I merely said that, if you squint, you could see it as a clumsy, inadequate, and probably unintentional half-step in the direction of crimsonalucard's idea.