[OSM-dev] Complete history of OSM data - questions and discussion

[Lars Francke]

>> I understand that a lot of this data is
>> available throughout the web using old snapshots and diffs but this
>> comes in outdated formats and is by no way complete or easy to use.
>
> Keep in mind that while a full database dump will give you some things that
> are not in the old planet files, but the reverse is true as well - there is
> information in the old planet files (pre-0.5) that is not in the database
> and thus will not be part of a history dump. Specifically this applies to
> pre-0.5 way history. This is not really a big deal execpt for those who
> would hope to make "OSM history animations" going back farther than API 0.5.

I had not thought of that. When I first used OSM, segments were long
gone so I tend to forget those. There are a few planet dumps from
those time but none before 060403 and no diffs (which would be
required to fully reconstruct the history). While I'm of course
interested in the most complete history possible I don't know if this
data would be easy to integrate. As I understand it all the old
segments that weren't part of a way were converted to a way and all
0.4-ways were just migrated to 0.5-ways (segments to node reference).
I suppose segments that were part of at least one way were not
converted to a way?

So we'd need to:
- Find the segments for "previously unwayed segment"-ways and
incorporate their history into the way. As the new way starts at
version 1 this would have to be a hack (version 0, counting backwards
or something like that).
- For ways we'd need to find the history data of the segments they
were made of and "merge" that into the history of the way, again
requiring versions before "1"

I don't know if it is worth the trouble but on the other hand it would
be nice to have a complete history. Especially as this would have to
be done only once. But as I said: My knowledge of pre 0.5 times is
limited at best and I'd be happy if you/someone else could tell me if
what I wrote makes sense. I'd certainly be willing to have _a look_ at
this, too.

Thanks for pointing this out!

Lars