[OHM] Identity through time

[Richard Welty]

my quick thoughts...

names can be duplicated, so removing the years is just fine. start_date and
end_date need to be set. in Ghost Tracks, i have code in my javascript
display
widget that adds the years to the name for display purposes; if i put on my
RDBMS hat, duplication of data is bad so including years in the name when
they are already in start_date and end_date must be bad too.

consider using relations to combine related objects; it's also ok to use
super
relations to contain groups of relations that belong together. and feel free
to think about tagging beyond what is in the OSM wiki. OHM is going to need
tagging beyond OSM tagging for a lot of the temporal concepts, and right
now, when OHM is still small, is the to experiment.

so if you create a relation for a parish at a point in time, you can then
create a super relation to contain all variants of that parish. OSM does
something similar with the Interstate and US highway systems in the
US; the relations are generally broken at the state boundaries and
there is a superrelation for each numbered route containing all the
state-by-state relations. what i'm suggesting is simply a vertical
grouping through time rather than a lateral grouping in space.

On 4/29/15 5:05 AM, SK53 wrote:
> H Mattias,
>
> Just as OSM has no notion of a named road (it can be lots of linear
> pieces) and the named road is deduced by proximity, so in OHM we have
> no notion of a single object changing through time, instead such links
> need to be done by both geographical and chronological proximity.
>
> Te reason for this is fairly straightforward. In a full relational
> model the pieces of a road would be in a 1:m relationship with the
> road object. Similarly in a temporal relational database for a
> boundary there would be many entries each with a distinct
> non-overlapping time range. This type of direct relationship is not
> possible with tags, although you could use relations.
>
> What we do not know is how easy it is to pull boundaries for different
> time periods together.
>
> Jerry
>
> On 29 April 2015 at 05:20, H MK <sockenkartor at gmail.com
> <mailto:sockenkartor at gmail.com>> wrote:
>
>     Hello everybody!
>
>     In the Stockholm area there are now boundaries for many
>     ecclesiastical parishes. In the city of Stockholm, the census
>     districts for the time they existed (1877–1926) should be done,
>     even if they need a lot of fact checking.
>
>     In order to separate different areas of the same entity, I have
>     named both the parishes and the census district with the years
>     they had that territorial extension. This is not satisfactory.
>     Reasonably, a parish is the same object after a minor territorial
>     change. As it is now, they become a new object whenever there is a
>     change. Or, is it ok to have several objects with the same name? I
>     would like to strip the years from names.
>
>

-- 
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