[OSM-talk] Tagging schema

Lester Caine lester at lsces.co.uk
Mon Oct 5 12:25:37 BST 2009


David Earl wrote:
> On 05/10/2009 11:43, Lester Caine wrote:
>> Rather than all these separate elements, tag values should form part 
>> of the tagkey object, and descriptions can be added at any level. I 
>> need to find the link to a good example, but
>>
>> <tag name='barrier' type='value' relevantto='node'>
>>      <tagvalue name='gate' />
>>      <tagvalue name='bollard'/>
>>      <tagvalue name='bollards'/>
>>      <description lang='en'>one or a series
>>      of short posts for excluding or diverting motor vehicles from a
>>      road, lawn, or the like</decription>
>> <tag/>
>>
>> But I suspect this is just a misunderstanding, as a scheme needs to be 
>> defined in .xsl. 
>> http://www.cabinetoffice.gov.uk/media/260545/BuildingStructure.xml is 
>> a good example of a definition of a building with enumerated tag 
>> values. I was trying to find the one that goes with 'landuse' but I 
>> don't have time ... need to be on the road by 1 ...
> 
> You're probably right - this was only a first attempt at suggesting the 
> principle.
> 
> In practice, the actual representation would be as database tables, and 
> this gets exposed through the API as XML. I would think the values would 
> typically be in a separate table, which is why I wrote it the way I did, 
> but the API doesn't have to deliver it separately as I wrote it.
> 
> I think you'd still want to be able to filter descriptions and possibly 
> other aspects by selected language to limit the size, but that's a minor 
> detail.

If one ignores the 'XML' then things are very much easier, and yes there 
would be table for 'descriptions', with a language flag as well as the 
'id' for the description. Lookup would return a selected language or 
English if there is no alternative. THIS table would simply be used by 
anything that need to return a text string - and needs it translating - 
not just descriptions ;)

I think though - we need to define a proper xsl schema wjjjjjich can be 
used WITH the tag data :(

-- 
Lester Caine - G8HFL
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