[OSM-talk] 'Allowed data'

[Lester Caine]

Andy Street wrote:
> 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!

Changes to details on the object would be covered by the changelog entries. At 
this stage simply a date that physical building came into existence would be 
nice. That only the current view of the object is provided is what 'The Data' is 
designed to supply, and in this instance the start_date is when the building 
physically appeared ...

You are perfectly correct that there are more start_dates needed, but starting 
today, any information change such as 'The Mapper Rest'->'The Mappers Arms' 
would be fairly accurate using the changelog dates. When it is scheduled to 
change at a future date, we have no means of recording that data. 'The Data' 
does not do history even if it relates to live data? We have to make those 
changes in real time rather than relying on the API serving the time correct view!

-- 
Lester Caine - G8HFL
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