Dependencies vs. unknowns when sequencing

A good question came up from a long-time Shape Up adopter:

I’ve noticed you mention two slightly different methods for sequencing:

- The interrelationships diagram
- Getting to the most unknowns first

Have you landed on a preference yet? Are there circumstances where one is better than the other?

To answer, here's an example from a project I'm working on now.

I have six scopes left. This project is very time sensitive, and I'm afraid that if I hit a problem too late or in the wrong order I'll regret it. So first I did interrelationship:

Then I foliated it to a causal diagram, by starting with the the things that have no outputs and working upwards from them:

This showed me what had to be done first in terms of dependencies.

But notice how `Pitch display` `Clean up` and `Step robustness` were all possible starting points. Which one should I work on first to allow the most time to solve it?

At this point I switched gears and asked about unknowns.

It turned out that the `Pitch display` path was well understood but `Step robustness` had a big unknown. If I didn't solve `Step robustness`, the whole project wouldn't work!

So I flagged that as unknown and moved it up in the sequence:

I hope this clarifies how dependencies and unknowns both play into sequencing. They're like two different dimensions that affect the decision.

Sometimes I only emphasize asking about unknowns because I assume programmers already think about dependencies. In cases where the dependencies aren't obvious, I reach for the interrelationship tool to spell them out.

(The translation from interrelationship to causal diagram is something new I'm experimenting with. For more on the interrelationship tool see Small Tools for Shaping and this LinkedIn post by Chris Spiek.)