[OSM-talk] Orphaned Relations

MP singularita at gmail.com
Mon Jul 18 22:28:54 BST 2011


On Mon, 18 Jul 2011 16:05:29 +0100, Ed Loach wrote:
>> Relations
>> without
>> members can be used intentionally,
>
> Can you give an example, please? Because I've tried and failed to
> think of any. Perhaps I'm just getting hung up on the name "relation"
> as something which groups its related members in some way defined by
> the relation's tags (while not being used as a category).

For example in Prague there is relation for transport network which 
contain empty relation for some tram lines - those are not operational 
currently due to some constructions, but once these constructions are 
finished, they can be easily restored to previous state (just dig up 
some older version of the relation from history, check it and save it)

There are quite rare uses for empty relation (but being a member of 
other relation) and mostly these uses are temporary.
Since if you download some data by some given bbox, you will get that 
empty relation (along with some other data).

But relations that contain no members and themselves are not members of 
nay other relation are "invisible" - they are not contained in any 
bounding box, they do not affect rendering, routing or anything and 
basically you can download them only by ID (or parse them from planet 
dump). So these are basically useless ....

Martin



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