[Tagging] Permanent IDs RFC (was part_of:wikidata)

Yuri Astrakhan yuriastrakhan at gmail.com
Thu Nov 30 19:56:38 UTC 2017

> If you edit a road, a new one would be created and would point to its
> invalidated ancestor. Recursively chasing previous ID pointers, you
> would eventually have an object without an ancestor. ID of that object
> would also be permanent ID of the successor objects. This will also
> solve road split problems as multiple objects can point to the same
> ancestor.

Erikn, if I understood you correctly, you are proposing the data structure
to generate and track IDs.  I think there are several issues:
* determining feature ID requires O(N) - linear search through history.
* given an ID, if you want to examine what it points to, you have to
assemble the whole tree of descendants to determine all of the leafs, and
test if they still exist or were deleted. Which also means that instead of
a human-currated single relation for the multi-segment road, and a single
list of tags, you are now looking at a set of objects, each with its own
list of tags.
* Download must contain an entire OSM change history to work with the IDs
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