# Objective
Our strategy for storing observers is made up of several moving parts,
which are ultimately fairly simple nested HashMaps.
These types are currently `pub`, but lack any meaningful way to access
this data.
We have three options here:
1. Make these internals not `pub` at all.
2. Make the data read-only accessible.
3. Make the data mutably accessible.
## Solution
I've opted for option 2, exposing read-only values. This is consistent
with our existing approach to the ECS internals, allowing for easier
debugging without risking wanton data corruption. If one day you would
like to mutably access this data, please open an issue clearly
explaining what you're trying to do.
This was a pretty mechanical change, exposing fields via getters. I've
also opted to do my best to clarify some field names and documentation:
please double-check those for correctness. It was hard to be fully
confident, as the field names and documentation was not very clear ;)
## Testing
I spent some time going through the code paths, making sure that users
can trace all the way from `World` to the leaf nodes. Reviewers, please
ensure the same!
## Notes for reviewers
This is part of a broader observer overhaul: I fully expect us to change
up these internals and break these shiny new APIs. Probably even within
the same cycle!
But clean up your work area first: this sort of read-only getter and
improved docs will be important to replace as we work.
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