Thank you! Your detailed explanation is very helpful! Do you know of any application which uses negative version or changeset numbers? Negative ids are common (e.g. JOSM outputs) but are there negative versions/changesets?
-------- Original-Nachricht -------- > Datum: Wed, 01 Jun 2011 15:34:13 +0200 > Von: Frederik Ramm <frede...@remote.org> > An: dev@openstreetmap.org > Betreff: Re: [OSM-dev] Difference between osm and osmChange formats > Hi, > > On 05/31/11 23:43, Sergey Galuzo wrote: > > Obvious differences between full and change are explicit > > create/modify/delete tags. > > We have full history OSM files and normal OSM files (both use .osm > extension and <osm>...</osm>), and we have simple diffs and replication > diffs (both use .osc and <osmChange>...</osmChange>). > > Normal OSM files never have a "visible" attribute, and they contain at > most one version of every object. > > Objects in full history OSM files contain a "visible" attribute, and > these files may contain different versions of the same object, with at > most one having visible=true. If there is a version with visible=true, > it will be the highest numbered version of that object. They do not > necessarily contain a full sequence of versions, i.e. you could have a > full history file that only has versions 2 and 5 of something. > > (There are also .osm files as written by the JOSM editor; these do not > have a "visible" attribute but may have an "action" attribute which, if > set to "delete", has a similar effect. This is a niche case.) > > The diffs contain <delete>, <modify>, and <create> blocks. A version in > <create> is usually 1. (Current implementation means it is *always* 1 > but this could be changed; it is not specified in the API that the first > version of something must always be 1.) A version in <create> or > <modify> can never have visible=false. > > If you have full replication diffs then one diff can contain the same > object multiple times, with different version numbers. It is possible > for the same object to appear in the <create>, <modify>, and <delete> > section of the same replication diff. Versions are not guaranteed to be > sorted, i.e. you could first encounter version 6 in a <delete> block and > later encounter version 5 in a <modify>. > > Since multiple edits are conflated in a simple diff, it is possible that > a simple diff contains an object as version 2 in a <modify> block but > the consumer has never before seen that object (because the version 1 > that would have been in a <create> has happened in the same diff > interval as the modification to version 2). > > In short, your assumption > > var changeTag = !Visible ? "delete" : Version == 1 ? "create" : "modify"; > > is mostly true but it depends very much on the context in which you want > to use it; there's a lot of things to trip you over. > > Bye > Frederik > > _______________________________________________ > dev mailing list > dev@openstreetmap.org > http://lists.openstreetmap.org/listinfo/dev _______________________________________________ dev mailing list dev@openstreetmap.org http://lists.openstreetmap.org/listinfo/dev
