"This business of arrows is a tricky one"

—Dependency Graph for Knowledge

The best discussion I've seen on the challenge of deciding which way to draw the arrows is from Edward Tufte, in the book "Beautiful Evidence" -- and available online here: Links, Causal Arrows, Networks

He centres the discussion on this diagram (this graph, this infographic... what do we call this now? Tufte calls it a diagram and an "art chart" ! nice.)

Arrows in this diagram align with the "arrow of time" - event A caused or contributed to event B.

But thing A did not touch thing B. Thing A could never touch thing B, it was never aware of the existence of thing B, which was in the distant future.

Is it fairer to say that thing B references thing A, and to draw the arrows in the reversed order?

References

• Edward Tufte forum: Links, Causal Arrows, Networks

See also

• Dependency Graph for Knowledge
• 7 Bridges of Königsberg