mirror of
https://github.com/nostr-protocol/nips.git
synced 2024-11-14 07:49:07 -05:00
142 lines
3.6 KiB
Markdown
142 lines
3.6 KiB
Markdown
NIP-xx
|
|
======
|
|
|
|
References to previous events
|
|
-----------------------------
|
|
|
|
`draft` `optional` `author:milahu`
|
|
|
|
Events can contain references to previous events.
|
|
|
|
Implementation
|
|
--------------
|
|
|
|
Each reference to a previous events consists of
|
|
|
|
- the distance between this event and the previous event, as an integer number, greater-or-equal than 1
|
|
- the ID of the previous event
|
|
- optional: relay URL
|
|
|
|
The choice of distances is arbitrary.
|
|
Some choices:
|
|
|
|
- exponentially increasing distances, for example: 1, 10, 100, 1000, 10000, ...
|
|
- linearly increasing distances, for example: 1, 10, 20, 30, 40, 50, ...
|
|
- random distances, for example: 1, 15, 32, 58, 93, 139, 185, ...
|
|
|
|
```json
|
|
{
|
|
"id": ...,
|
|
"kind": ...,
|
|
...,
|
|
...,
|
|
"e_prev": [
|
|
[<previous event distance>, <previous event ID>],
|
|
[<previous event distance>, <previous event ID>],
|
|
[<previous event distance>, <previous event ID>, <previous event relay URL>],
|
|
...
|
|
]
|
|
}
|
|
```
|
|
|
|
Soft chain of events
|
|
--------------------
|
|
|
|
This is useful to build a "soft chain" of events, so the recipient can detect missing events.
|
|
|
|
Events can go missing because of
|
|
|
|
- political reasons (censorship)
|
|
- technical reasons (data loss)
|
|
|
|
Redundancy
|
|
----------
|
|
|
|
Each event can contain multiple references to previous events.
|
|
|
|
The next-previous event (distance 1) SHOULD always be referenced.
|
|
|
|
The number of referenced previous events is arbitrary.
|
|
It can be as low as one previous event, or as high as all previous events.
|
|
|
|
This gives a tolerance for missing events:
|
|
When a previous event is missing, the recipient can seek back to another previous event.
|
|
|
|
Forward search for missing events
|
|
---------------------------------
|
|
|
|
When an event is missing, and cannot be found on any other relay, the recipient will want to "seek forward" from another previous event.
|
|
|
|
Example:
|
|
The last received event `E0` contains references to previous events `[E1, E3, E7]` with the distances `[1, 3, 7]`.
|
|
`E1` is missing (cannot be found on any relay).
|
|
`E3` is found and received.
|
|
|
|
Problem:
|
|
How can we find `E2`?
|
|
We only know the distance `2` (relative to `E0`) of `E2`, but not the event ID of `E2`.
|
|
Usually we would use the previous-event-reference with distance 1 of `E1`, but we dont have `E1`.
|
|
|
|
Solution:
|
|
We ask relays for events with references to `E3` or `E7` (or any other previous event in this chain).
|
|
So relays SHOULD implement a "lookup of events by reference-to-previous-events".
|
|
|
|
Limitations
|
|
-----------
|
|
|
|
Missing events can be detected only for past events, relative to a received event.
|
|
|
|
Adoption
|
|
--------
|
|
|
|
Events created before the adoption of this NIP can be referenced in future events.
|
|
To improve space-efficiency, it can make sense to distribute these back-references across multiple events ("sparse chains", "fragmented chains").
|
|
|
|
Inconsistencies
|
|
---------------
|
|
|
|
There is no guarantee that the merging of multiple previous-events-lists produces a consistent chain of events.
|
|
Eventual inconsistencies can be resolved by sorting events by time or event ID.
|
|
(Multiple diverging chains can be merged by sorting events by time or event ID.)
|
|
|
|
Such inconsistencies allow modification of the chain (insertion or deletion of previous events), so the chain is mutable.
|
|
|
|
Visualization
|
|
-------------
|
|
|
|
Clients should visualize:
|
|
|
|
- the reference to the first previous event
|
|
- missing previous events
|
|
|
|
If there are many missing previous events, these can be collapsed to a "N missing events" block.
|
|
|
|
TODO: rename key
|
|
----------------
|
|
|
|
```json
|
|
{
|
|
...,
|
|
"e_prev": [
|
|
...
|
|
]
|
|
}
|
|
```
|
|
|
|
Rename the key to ...
|
|
|
|
- previous_events
|
|
- e_prev
|
|
- prevs
|
|
- history
|
|
- soft_chain
|
|
- chain
|
|
|
|
Keywords
|
|
--------
|
|
|
|
- blockchain
|
|
- censorship-resistance
|
|
- tamper-proof
|
|
- append-only
|