OpenStreetMap
I wonder if people use these tags, and how? I usually use them to tag landuse=construction to mark when the construction work started and when it is estimated that all work will be complete.
When end_date=* comes I usually check again and change the tag from landuse=construction area into a playground, a highway or something similar. I also change the start_date key.
Discussion
Comment from Zverik on 21 October 2011 at 18:46
In Russia, we use opening_date=* to mark the end date of road works (as stated on an information board), and check_date=* to store the date of last status check.
Comment from balrog-kun on 22 October 2011 at 00:43
I think the idea of start_ and end_date was so that you could leave this landuse=construction in the database forever, as well as map the playground before it even exists, and have all of the programs concerned with just the current data ignore them at any time outside of the start_date - end_date period. At the same time programs which are concerned with historical information could use this data in different ways.
Obviously there are many arguments against doing that or against historical mapping inside the OSM database and it's hard to decide one way or another. For construction works I have seen a more plausible tagging proposal somewhere on the wiki, using the three tag suffixes:
:ata_create=
:ata_modify=
:ata_delete=
and the tag ata_delete= which would list operations that should automatically happen to a given tag or the entire object on a given date. Someone could then run a bot to execute those commands. Again there is a couple of arguments against this, but I've seen it used sometimes.
Comment from balrog-kun on 22 October 2011 at 00:45
(The values of all of these tags would contain a future date for the operation, I wrote that using angle brackets and they were filtered out of my comment above)
Comment from EdLoach on 22 October 2011 at 08:01
I don't use them, but was considering trying to get in touch with local historians to get them to give me approximate years of build of houses (and roads?) so I could tag them in some way to show how the town has grown over time by creating an animation from the OSM data. Perhaps built_date would be appropriate. As I've not done it yet, I've not searched to see whether there is any tag already suggested for year of build in the wiki.
Comment from emj on 22 October 2011 at 08:02
@Zverik Maybe opening_date is interesting, but there are not docs on it. Do you mean that you tag ongoing works with opening_date=* to signify when the construction works are supposed to be finished and the road will be open for traffic?
@balrog-kun: Since that use of end_date is not possible at the moment, I've used it to leave a reason why I delete something. So I might do this:
1. tag "way 12345" with end_date=2011-09
2. upload
3. delete "way 12345"
or as I did above
1. tag landuse=construction with end_date and start_date
2. when end_date comes change the tags to be playground without an end_date
This makes it possible to have different versions, if you use history extracts.
I don't know where those ":ata_*" keys are documented, and I'm not much for bot deletion, since construction projects, as many other kind of projects, tend to be delayed.
Comment from emj on 22 October 2011 at 08:39
@Edloach: Yeah built_date is interesting, but when working with houses in a city you will have some buildings which have been rebuilt..