Interesting thought to add time ranges to tags, re "All changes to attributes
as described above must each have a time associated with them.".
And I like Christian's suggestion of modifying existing tags, in a similar way
to name localization. That makes sense in the OSM universe.
It can also apply to uses of entity, like a building that starts off as a
historic home, becomes a museum or an office.
And to link an entity that changes geometry over time, well, relations could be
adapted for this.
Confidence factor is important to record, and that could sit fine in tags as
well.
The trick for all this is how does it can translated into schemas for
rendering, geocoding, etc. What's an efficient way to represent these things in
postgres, in order for mapnik to make tiles?
Once we get the infrastructure ready, I'm going to work on a very small area
right in my neighborhood. http://www.si.edu/oahp/holthous/start.htm
There's a private house, that became offices for the National Zoo. And
post-Emancipation black cemetery, now controversially a park and boundary area
to the zoo.
-Mikel
ps On a non-geographic tangent, I was thinking about the different names given
to the same historic event in different languages/nations/cultures. For
instance, Russian calls World War 2, the "Great Patriotic War". The
Palestinians call the founding of Israel the "Nakba". Has anyone seen any open
collection of the different linguistic perspectives of history?
* Mikel Maron * +14152835207 @mikel s:mikelmaron
>________________________________
> From: Brad Thompson <[email protected]>
>To: [email protected]
>Sent: Monday, January 21, 2013 8:32 PM
>Subject: Re: [Historic] Temporal Tagging
>
>
>The issue of how to handle changes in names, locations, and shapes (for
>territories, building footprints, etc) has been a favorite topic of mine in a
>few discussions to date. The problems can quickly become complex, but I think
>a simple schema could encompass all possible historical scenarios. I'm happy
>to share the observations / conclusions, which have generally been the
>following:
>
>
>1) Unlimited Changes to All Attributes: The schema should allow the recording
>of an unlimited number of changes to any attribute of any entity. No attribute
>can be used as a unique identifier, like 'name' or 'address' or even
>location-based attributes, because throughout history, all of these things can
>change. Therefore, a truly unique identifier must be assigned to each entity.
>Additionally, buildings are moved, streets are renamed, rerouted, and
>renumbered. Tim, as you've pointed out, this has happened many times to some
>entities. Therefore, a schema that simply allows for a single 'old-name' isn't
>flexible enough. All changes to attributes as described above must each have a
>time associated with them.
>2) Confidence Factors: Because historical data inherently entail uncertainty,
>there should be a method of assigning a confidence factor to any attribute.
>(This feature has no purpose in realtime mapping, because all data can be
>verified against actual conditions.) This confidence factor would be
>applicable both to attributes like names as well as times. For names, for
>example, "we think the name of this hill was Telegraph Hill, but there are
>conflicting reports that claim it was called Signal Hill, so we assign a 60%
>confidence factor to Telegraph Hill and a 40% confidence factor to Signal
>Hill". The renderer could then decide how to display the name(s). For times,
>for example, "we know this hill changed name from Loma Alta to Telegraph HIll
>sometime between 1848 and 1852, but we don't know for certain when, so we
>assign the date of the change as January 1, 1850 and give it a confidence
>factor of 4 years (creating a buffer with a temporal diameter of 4
years around that date). This idea is critical, because it allows conflicting
reports and developing research to be displayed alongside well-established
facts.
>3) Spatial and Non-Spatial Entities: Because shapes (nodes, etc.) cannot be
>used as unique identifiers the way they can for realtime mapping, there exists
>a need to create a distinction between spatial entities and non-spatial
>entities. This way, each spatial permutation (or version) of an entity, like a
>building or a road or a territorial boundary, can have a distinct shape that
>is still linked to the nonspatial entity that represents the concept of its
>agreed-upon identity. For example, 'United States of America' would be a
>nonspatial entity with a start date of 1776 and no end date. But linked to
>that entity would be dozens of spatial entities, because the boundaries of the
>United States have changed dozens of times, therefore changing the shape,
>through small border edits or territorial acquisitions. Each of those shapes
>would have its own start and end time, and the map would display the correct
>shape as determined by the time being viewed.
>
>
>Obviously, we're talking about a dramatically different way of recording place
>data, but in my view, these levels of detail are critical to making a viable
>historical mapping platform where multiple types of data can be shared and
>displayed. Looking forward to hearing everyone else's thoughts on this.
>
>
>Brad Thompson
>Pastmapper
>_______________________________________________
>Historic mailing list
>[email protected]
>http://lists.openstreetmap.org/listinfo/historic
>
>
>
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