[Tagging] Data metamodels

Colin Smale colin.smale at xs4all.nl
Sat Jun 6 14:36:38 UTC 2015


On 2015-06-06 15:55, Daniel Koć wrote: 

> W dniu 06.06.2015 11:29, Colin Smale napisał(a):
>> Time to work towards an updated metamodel, with:
>> * Multiple values (lists of values - sorting out the semicolon
>> business?)
> Sure!
>> * Complex values (data structures - formalising the namespace syntax?)
> Any example? I don't know what are you talking about.

Take addresses as an example. An address is composed of a set of fields,
like house number, postcode etc. These are mapped into the OSM tags
"addr:street", "addr:postcode" and so on. You can consider an "address"
to be a reusable definition, which can be used in many contexts. The
current OSM syntax using the colon says that *this* use of "street" is
in the role of a part of an "addr", and is semantically distinct from a
"street" used as part of some other collection of values. All the data
fields which are part of an "addr" are grouped together by the common
prefix "addr:". But this usage of the colon to separate the namespace ID
from the field is not actually part of the data metamodel. The key
"addr:housenumber" is just a string and the colon is nothing special at
the moment. It all hangs together with a sort of unwritten gentleman's

>> * Simple Polygon as a basic type ("under construction" without any
>> tangible progress for years)
> What do you mean? This issue maybe?:
> http://wiki.openstreetmap.org/wiki/The_Future_of_Areas [1]

That is exactly what I mean. That article was created in 2011 and has
essentially gone nowhere since then. 

> These are all real-life things that cause a lot of energy to be
> expended in OSM, simply because we don't have a way of representing
> them in the metamodel.

> You're right. I also argue we need better category system, exactly because we loose a lot of energy for trying to put some real-life objects into too narrow and fixed categorization model.
> Time to take things to the next level!
> Any practical hints how to do it?

This is where it gets problematic. Any attempt in this direction will
necessarily restrict the freedom of mappers, by saying there is a right 
way and a wrong way to do something. The theoretical side of creating an
information metamodel is the easy bit. Getting the community to buy in
something that will need support from every stakeholder in the OSM
ecosystem is a challenge that is better picked up by someone else with
diplomacy and patience than me... It's part of what I do for a living,
and I try to pick my battles carefully. 


[1] http://wiki.openstreetmap.org/wiki/The_Future_of_Areas
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