[OSM-dev] Binary OSM; the first pass encoder

[Stefan de Konink]

Marcus Wolschon wrote:
> cool to see some progress here.
> If you decide on an index-format I can implement a DataSource for
> Traveling Salesman for it (however any updates can only be appended).

The two problems I see;
- In order to allow updates there should be some form of 'updatable space'.
- If this space is not present it might be good to have one file that 
contains *all* strings, another one that contains the rest of the data, 
and maybe a final client-side generated index on both of them.

> Did you have a look at
> http://wiki.openstreetmap.org/index.php/User:MarcusWolschon%5Cosmbin_draft
> ? 

Your format, as well the mobile format is not data compatible with the 
XML file. And impose limits on attributes. Next to this my overhead per 
tag is one byte, and length is impled for the record.

> I am trying something similar but with fixed length records and back-links
> from node to way to allow updates to be applied to the file.
> 1.4GB-135MB is nice but you still don't want to download 135MB every day to
> have an up-to-date netherlands-file (let alone to do this for the planet).

135MB (gzip XML) -> 78MB (bzip2 bin)

We are just looking at the possibilities to binary diff the files, just 
to allow partial updates. By XORing them on the source present at the user.

> I was quite occupied with another open-source-project of mine and
> switching jobs but now I should have the time to finish implementing
> my own  proposal in code and test it's performance.

:) good luck :) if you want to team up to write the ultimate code, just 
send a private mail.


Stefan