[OSM-dev] api0.6 - only one value per key?

[Andreas Kalsch]

marcus.wolschon at googlemail.com schrieb:
> On Wed, 28 Jan 2009 00:07:20 +0000, Simon Ward <simon at bleah.co.uk> wrote:
>   
>> [Moved to dev; followups to dev]
>>
>> On Tue, Jan 27, 2009 at 10:58:25PM +0000, Ævar Arnfjörð Bjarmason
>>     
> wrote:
>   
>>>> I think multiple keys with the same name should be allowed for a
>>>> node/way/relation.  AFAIK it's only the editors that don't currently
>>>> let
>>>> you do this.
>>>>         
>>> Yes, the API and data format supports it, but only for another 2
>>> months or so until we switch to 0.6 where it won't be allowed.
>>>       
>
> I cannot find any such restriction in
> http://wiki.openstreetmap.org/wiki/0.6 .
>
> Could someone please clarify this?
> I implemented no changes to attribute-handling
> for the 0.6-support in my software and need
> to know if I have to explicitely disallow this
> to happen, write test-cases,... .

I would not restrict this. For qualifying keys like "highway" or 
"amenity" it makes sense, but what about "image" - there could be 
several associated to one feature. My proposal is:

- Make keys case insensitive and give them an id internally.
- Make tags from a key id and a case sensitive value, the tag has an id, 
too.

I have implemented this in an experimental way and it makes sense in any 
way. Let me know, if you are interested in SQL. The effort to manage 
this is a little bit higher, but you have a consistent data model which 
is more lightweight and quicker for lookups (PK lookup is better than 
k/v lookup). What about this?

Question: I have found a PGSQL schema for v0.6 where key and value are 
TEXT fields. Is the length of 255 still correct for v0.6?
There are some imported values which are longer than 255 characters.

Andi