Proposal:Composite Tag: Difference between revisions
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Composite tags can be used to add [[Conditional restrictions|time or vehicle class restrictions]] to a tag. |
Composite tags can be used to add [[Conditional restrictions|time or vehicle class restrictions]] to a tag. |
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== Statistics == |
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| {{#tag:osmtaginfo||rtype=composite_Attribute}} || {{#tag:osmtaginfo||rtype=composite_attribute}} |
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== See also == |
== See also == |
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Revision as of 21:16, 10 March 2013
Composite tags can be used to add time or vehicle class restrictions to a tag.
For example:
no cycling 1000 to 1630 no HGVs 2200-0600
They could also be used to create every imaginable grouping of tags, or "structured tags". (This was indeed discusssed when relations generally were still at the "proposal" stage and were called "entities".) For example, if you have a road with an adjoining footway (or cycleway) and you don't map them as individual ways, then you lose the ability of giving differing attributes to the road and the footway. Say the road was asphalted but the surface on the footway was gravel, how would you express that? People have suggested various kinds of tag structuring, like
surface:road=asphalt surface:footway=gravel
or
surface=road:asphalt,footway:gravel
It is, however, also possible to - while not creating a separate geometry for the footway - to create a separate object representing the footway which then contains all the tags which apply only to the footway. So you would have the way describing the road:
Way #123456 highway=secondary surface=asphalt oneway=true nodes=345,789,333,777,444...
and you could use a relation as a generic tag container object to group the footway specific information:
Relation #55434 highway=footway surface=gravel oneway=false
The remaining question is how to link this relation to the way in question. The most straightforward way would be a forward link from the way to the relation, like a tag that contains a relation value: "footway_left=#55434". Since this is not supported, we would have to add a backlink from the relation, such as:
Relation #55434 highway=footway surface=gravel oneway=false members: role=left_of,type=way,id=55434
(Or, perhaps, a better role description...)
Tags
The tags field holds key/value pairs for all the required tags, frequently a period of applicability or time of applicability and the tag(s) to which the restriction should be applied.
| Key | Value | Discussion |
|---|---|---|
| type | composite_Attribute | |
| note |
Members
A list of the ways to which this composite tag applies
| Way or Node |
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Statistics
See also
Conditional restrictions, useful for the "no cycling 1000 to 1630 no HGVs 2200-0600" idea