I have thought that Sci-Fi / speculative fiction stories are in a really good position to be categorised by something similar to Aarne–Thompson–Uther index.
Consider some basic stories like:
* a person travels backwards through time to prevent a tragedy.
- By doing so they cause the tragedy to occur.
- On returning to their own time they discover the tragedy was necessary for their society.
* a person travels backwards in time to meet their hero.
- they discover the person didn’t exist and become them.
- they discover the person isn’t as heroic as they hoped and coach them.
Just four examples, but I’m sure you can see how many stories fit into each.
Another interesting classification discovered from Propp's Wikipedia entry: Aarne–Thompson–Uther Index of folktale types: https://en.wikipedia.org/wiki/Aarne%E2%80%93Thompson%E2%80%9...