Time-varying symlink-like logging of one entity to two paths

[genemerewether]

Would it be possible to express the following without logging the same data twice on two paths:

At time t0, entity E refers to sample A
At time t1, entity E refers to sample B

Sample A is only logged at t0
Sample B is only logged at t1

Concrete use case:
A & B are training samples. We'd like to both:

1. be able to check performance on A & B over time (visualize A, or visualize B - timeline would indicate when they were presented during training)
2. see the samples in the order they were presented during training (visualize E and seek through time)

[Wumpf]

Looks like we haven't written this down anywhere yet, but logging of links is something that came up internally a bunch of time already 👍