[OSM-talk] Relations not always brilliant

[David Earl]

On 07/04/2008 11:11, Frederik Ramm wrote:
> Hi,
> 
>> But this is kind of the point - if you are able to automatically  
>> create the relations (and presumably automatically fix them if  
>> someone makes the way tags inconsistent with the relation tags)  
>> with very little effort, is there a good reason to create them in  
>> the first place rather than deriving that data as and when you need  
>> it?
> 
> I assume it will usually be easier to check a machine-readable  
> relation than to compare tags. 

And to take the A11/A14 example again, if the A11 in effect disappears 
where it is coincident with the A14, the A11 is discontinuous. How do 
you therefore distinguish from the ref alone that the pieces of the A11 
in the UK are different from the A11 autobahn in Germany. Determining 
which country they are in is hard (even harder when there is no water 
between them). And the European E route numbers cross national 
boundaries (actually there's an example where UK roads really do have 
more than one ref, though it's unlikely we'd tag them because there is 
no evidence of this on road signs).

David