I found a big problem in OHM: the dates.
What the documentation says
In fact, when we check the wiki for know how tag the value changements of a key, we found this page: Comparison of life cycle concepts - OpenStreetMap Wiki
This page proposes some way to do, but doesn’t say explicitly wich one should be used.
So, I tried some of them (for exemple on this way), but it doesn’t appear on the map.
I think this subject is necessary to clarify in order to harmonize the way to map, and the possibilities to reuse the datas.
Actually, the tags whose working with the map are
start_date=. But the problems for these tags are that they define the strat-date and the end-date of the totality of the object, however, we need some tags for tag each small change of the object. The most currency exemple is the name of the objects, wich cans change many times. But this is valid too for each tag of a object.
An exemple of the size of the problem
Here is an exemple:
This objet is a French railway. During his “life”, it knew a lot of changes:
- around 6 different signallings
- around 10 differents maxspeed
- a different number of track
- a different type of electrification
- a different loading gauge
- differents ref
So, for me, it’s urgent to clarify the situation.
Personally, I think that the keyname:DATESPEC= concept is the more advanced and clear one, because it permit to precise every different tags and changements.
However, I think it’s necessary to develop the concept for map objects with an uncertain date, like something where we know a century of beginning, but no more precise.
For exemple, we could tag the start date of an road created in the 3rd century like that:
Before Jesus Christ (or our era)
Today, this system propose to write a tag like that:
KEY:YYYY-MM-DD-YYYY-MM-DD=VALUE, with the first YYYY-MM-DD as the start date, and the second as the end date.
If we wanna tag an object from before JC, or the year 0, this concept doesn’t give the way to do.
So, the first idea should be to add an “-” symbole before the year. In this case it give something like that:
KEY:-YYYY-MM-DD–YYYY-MM-DD=VALUE (in the case where the start date and the end date are before JC).
Here is my problem and the solution I propose.
Please forgive my English mistakes, and I’m impatient to read you answers.