OSM XML
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Basics
XML is a so called meta format to provide even human readable data interexchange formats. Various file formats use this HTML tree like structures to embedd their datas like SVG, ODT,...
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OSM XML file format
The major tools in the OSM universe use an XML format following this XML schema definition that was first used by the API only. Basically it is a list of instances of our data primitives (nodes, ways, and relations) that are the architecture of the OSM model.
Here is a shortened example of a complete OSM XML file:
<?xml version="1.0" encoding="UTF-8"?> <osm version="0.6" generator="CGImap 0.0.2"> <bounds minlat="54.0889580" minlon="12.2487570" maxlat="54.0913900" maxlon="12.2524800"/> <node id="298884269" lat="54.0901746" lon="12.2482632" user="SvenHRO" uid="46882" visible="true" version="1" changeset="676636" timestamp="2008-09-21T21:37:45Z"/> <node id="261728686" lat="54.0906309" lon="12.2441924" user="PikoWinter" uid="36744" visible="true" version="1" changeset="323878" timestamp="2008-05-03T13:39:23Z"/> <node id="1831881213" version="1" changeset="12370172" lat="54.0900666" lon="12.2539381" user="lafkor" uid="75625" visible="true" timestamp="2012-07-20T09:43:19Z"> <tag k="name" v="Neu Broderstorf"/> <tag k="traffic_sign" v="city_limit"/> </node> ... <node id="298884272" lat="54.0901447" lon="12.2516513" user="SvenHRO" uid="46882" visible="true" version="1" changeset="676636" timestamp="2008-09-21T21:37:45Z"/> <way id="26659127" user="Masch" uid="55988" visible="true" version="5" changeset="4142606" timestamp="2010-03-16T11:47:08Z"> <nd ref="292403538"/> <nd ref="298884289"/> ... <nd ref="261728686"/> <tag k="highway" v="unclassified"/> <tag k="name" v="Pastower Straße"/> </way> <relation id="56688" user="kmvar" uid="56190" visible="true" version="28" changeset="6947637" timestamp="2011-01-12T14:23:49Z"> <member type="node" ref="294942404" role=""/> ... <member type="node" ref="364933006" role=""/> <member type="way" ref="4579143" role=""/> ... <member type="node" ref="249673494" role=""/> <tag k="name" v="Küstenbus Linie 123"/> <tag k="network" v="VVW"/> <tag k="operator" v="Regionalverkehr Küste"/> <tag k="ref" v="123"/> <tag k="route" v="bus"/> <tag k="type" v="route"/> </relation> ... </osm>
See Data Primitives for details of the object categories.
See Map features about how real world objects are modeled and categorized.
The structure is the following:
- an XML suffix introducing the UTF-8 character encoding for the file
- an osm element, containing the version of the API (and thus the features used) and the generator that distilled this file (e.g. an editor tool)
See the /XSD, and /DTD pages for details of attempts to define the format in those languages.
Assumptions
If you develop tools using this format, you can be sure that:
You can not be sure that:
- blocks are there (e.g. only nodes, no ways)
- blocks are sorted
- element IDs are non negative (Not in all osm files. Negative ids are used by editors for new elements)
- elements have to contain tags (Many elements do not. You will even come across Untagged unconnected nodes)
- visible only if false and not in Planet.osm
- id or user name present (Not always, due to anonymous edits in a very early stage)
- Changesets have an attribute num_changes for (This was abandoned from the history export tool because of inconsistencies)
- version ordering is sequential (doesn't have to be)
JOSM uses an 'action' attribute instead of timestamp, version or changeset for new objects
Some #flavours might have other restrictions.
Tools
See Planet.osm and Import, Export, Convert
Flavours
There are a few different file formats currently in use, all with slightly different goals.
JOSM file format
Main article: JOSM file format
The file format was designed by the author of JOSM. It basically is a logical extension of the data sent from the server. What it adds is an indication of the origin of the data and the bounding box it comes from (if possible). It is actually more of a storage format of data downloaded along with changes made by the user.
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Supported by:
- JOSM
- Bulk_upload.py (read-only)
- Geo::OSM library
- osmconvert
- osmfilter
osmChange
Main article: OsmChange OsmChange is a file format was created by the author of osmosis and is a more general format for representing changes.
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When sorted properly this file is a continuous stream of changes that can be played in order. In osmosis the option --sort-change will put the change into streamable order. |
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Placeholders are proposed as an extension though they are not widely supported.
Supported by:
- Osmosis
- Bulk_upload.py (read-only)
- Geo::OSM library
- osmconvert
- osmchange (read-only)
- osmfilter
Technical features of change formats
This a list of things that are desirable in a change file format for exampe change sets
placeholders
Placeholders are a feature where objects that are created in the file can be used in the creation of the objects that depend on them. So a single file can create two nodes and join them with a segment without knowing beforehand the final IDs.
indication of origin
IDs used in OSM files can not be shared between servers. IDs are allocated by the server, not by clients. Thus it is useful if the change file indicates the source of any IDs used in the file.
streamable
Whether the file can normally be processed in a stream, without breaking referential integrity.
