[OSM-dev] Timestamp in PBF files

[Scott Crosby]

On Tue, Nov 20, 2012 at 6:51 AM, Frederik Ramm <frederik at remote.org> wrote:

> Hi,
>
> (message to dev list but explicitly Cc'ing Brett and Scott because I don't
> know if they follow dev)
>
>    about a year ago, Marqqs tried to have a discussion on how to add
> timestamps to PBF files and hardly anyone was interested.
>
> I've had a couple people ask me whether I could somehow add timestamp
> information to the PBF files that I produce for download.geofabrik.de so
> I'd be interested in solving this somehow.
>
> I really don't mind *how* it's done but I would really love to have one
> agreed way to place a timestamp in a PBF instead of everyone rolling their
> own.
>
> What's the current status of this discussion? Is there already an approved
> way to deal with this?
>

No status, but if anyone wants my opinion, when authoring the format, I
expected us to add metadata to planets, and expected it to be put into
OSMHeader as in the OSRM clone you linked to above. I would vote to
deprecate the use of the ISO timestring encoded into the optional_features
array, but continue to write to it to avoid breaking old installs of
Marqqs's tools. I also think that we have more than one notion of
timestamp. How does this sound:

message HeaderBlock {
  optional HeaderBBox bbox = 1;
  /* Additional tags to aid in parsing this dataset */
  repeated string required_features = 4;
  repeated string optional_features = 5;

  optional string writingprogram = 16;
  optional string source = 17; // From the bbox field
  optional sint64 timestamp = 18; // Unix-Time encoded into varint of
when the file was generated.
  optional sint64 mirror_timestamp = 64; // Unit-Time timestamp of the
last update the source. (used for mirroring)
}


What about adding other metadata or adding in a nanosecond timestamp while
we're at it?

Scott
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