[OSM-talk] 'Allowed data'

[Andy Street]

On Thu, 05 Dec 2013 15:20:58 +0000
Lester Caine <lester at lsces.co.uk> wrote:

> Martin Koppenhoefer wrote:
> >     I would like to request that 'start_date' is automatically
> > populated with ad the very least, the current date, but with an
> > option to update it based on what is being traced from?
> >
> > if you are refering to the tag "start_date" than I strongly oppose
> > this idea. Hardly ever will the start_date of an object be the same
> > than the time the mappers adds it.
> 
> I am referring to using 'start_date' is it is currently documented
> http://wiki.openstreetmap.org/wiki/Key:start_date
> At a very minimum putting a current timestamp in will give a starting
> point since we know it is valid today, although a future start date
> is also possible. It is creating the habit of populating it and
> encouraging the addition where it is known.

The start_date is the date that it feature came into existence not the
date it was mapped so automatically populating it will just lead to
junk data that is indistinguishable from the real valid data. What you
really asking for is an auto-generated start_date_sometime_before tag
but that data is already logged in the changesets.

There is also the matter of *what* started. Take the following example:

building=yes
amenity=pub
name=The Mappers Rest
start_date=2013-11-15

Was the building first opened on that date? or was it when the pub began
trading? Perhaps that was when the name changed? To do this properly
you'll need to automatically add a start_date_sometime_before tag for
every tag in the database!

-- 
Regards,

Andy Street