[Tagging] better classification systems

[Fernando Trebien]

On Fri, Feb 12, 2021 at 2:00 PM Colin Smale <colin.smale at xs4all.nl> wrote:
> What do we want to be able to get out of OSM?

This is always evolving, new applications come and go. [1]

> however OSM is mature now

Where there are many mappers (Europe and the Anglosphere), yes. In
most parts of the world, [2] no.

> Historically OSM has always wanted to make life easy for non-expert mappers and tended to exclude the needs of data consumers.

You can write complex software in a matter of days or months, but
mapping the world takes a lot more effort.

> OSM is relatively unique in that it tries to find global tagging for region-dependent concepts. Highway types for example use a list of values originating in the UK, and now we force every other country to fit into that system. Concepts like "unclassified" need explaining time and time again. We still don't have a mechanism for having defined regional defaults or implications (like highway=motorway implies foot=no in many places) other than the odd note in a wiki page, but that doesn't lend itself to automated processing.

This is one of the most debated topics. Years ago, I tried to study
the problem and come up with general rules, [3] but I was just trying
to figure out what would be best for mapping the area where I live.
Functional classification is adopted by the European Commission and in
North America, and as a result also in many other countries, which
turned out to be a rational choice in my area, and functional classes
can be somewhat easily mapped to the UK system. The problem is that
"function" is not as tangible as other characteristics, but it seems
to be what the commercial maps are trying to do. Years ago, OSM
started to classify roads by intended use and importance, [4] which is
closely related to the idea of function.

You can also create and use tags in OSM that reflect the data model
used in your own country. For example, you could actually add a
highway: [country code]=* with country-specific values. You can then
use this data to generate a map of your country.

> There are continuous discussions about how to put addresses in OSM. It doesn't take long to discover that the UPU, the Universal Postal Union, has already defined a universal data model for addresses, and for each country a map exists to and from the local address model to the canonical model (and also templates for layouts on envelopes etc). This universal data model may seem quite complex to some. I can handle it because I have an IT background, but many people may see it as over-engineered because they are only interested in the simple addressing used in (for example) Belgium. UPU S42 details here: https://www.upu.int/en/Postal-Solutions/Programmes-Services/Addressing-Solutions

This should probably be turned into a tagging proposal. [5]

> In summary, I think we need:
> 1) acceptance that the data is for computers and not intended for direct human consumption

Mappers are humans. Many of them are prosumers, that is, they consume
the data they produce. The data is for computers and for humans. [6]

> 2) more attention to what we want to get OUT of OSM and relatively less about putting stuff in there

Anything one wants. [7] Although the idea is that mappers will try
something new and interesting and, after a period of trial and error,
when their idea is finally mature, the leftovers will be cleaned
(sometimes very slowly).

> 4) a mechanism for defining a hierarchy of regional characteristics (defaults, implications etc)

Doesn't that already exist? However, like everything in OSM, it is
still a WIP. [8][9]

[1] https://wiki.openstreetmap.org/wiki/List_of_OSM-based_services
[2] https://wiki.openstreetmap.org/wiki/Humanitarian_OSM_Team
[3] https://wiki.openstreetmap.org/wiki/User:Ftrebien/Drafts/Generic_highway_classification_principles
[4] https://wiki.openstreetmap.org/wiki/Key:highway#Assumptions
[5] https://wiki.openstreetmap.org/wiki/Proposal_process
[6] https://en.wikipedia.org/wiki/Human-readable_medium
[7] https://wiki.openstreetmap.org/wiki/Any_tags_you_like
[8] https://wiki.openstreetmap.org/wiki/OSM_tags_for_routing/Access_restrictions
[9] https://wiki.openstreetmap.org/wiki/OSM_tags_for_routing/Maxspeed

-- 
Fernando Trebien