<html><body><div style="color:#000; background-color:#fff; font-family:times new roman, new york, times, serif;font-size:12pt"><div><span>Interesting thought to add time ranges to tags, re "</span><span style="font-family: arial, sans-serif; font-size: 13px;">All changes to attributes as described above must each have a time associated with them.". </span></div><div></div><div>And I like Christian's suggestion of modifying existing tags, in a similar way to name localization. That makes sense in the OSM universe. </div><div><span style="font-size: 12pt;">It can also apply to uses of entity, like a building that starts off as a historic home, becomes a museum or an office.</span><br></div><div><br></div><div>And to link an entity that changes geometry over time, well, relations could be adapted for this.</div><div>Confidence factor is important to record, and that could sit fine in tags as well.</div><div><br></div><div>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?</div><div><br></div><div><br></div><div>Once we get the infrastructure ready, I'm going to work on a very small area right in my neighborhood. <a href="http://www.si.edu/oahp/holthous/start.htm" style="font-size: 12pt;">http://www.si.edu/oahp/holthous/start.htm</a></div><div>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.</div><div><br></div><div>-Mikel</div><div><br></div><div>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?</div><div><br></div><div>* Mikel Maron * +14152835207 @mikel s:mikelmaron<br><blockquote style="border-left: 2px solid rgb(16, 16, 255); margin-left: 5px; margin-top: 5px; padding-left: 5px;"> <div style="font-family: 'times new roman', 'new york', times, serif; font-size: 12pt;"> <div style="font-family: 'times new roman', 'new york', times, serif; font-size: 12pt;"> <div dir="ltr"> <font size="2" face="Arial"> <hr size="1"> <b><span style="font-weight:bold;">From:</span></b> Brad Thompson <brad@pastmapper.com><br> <b><span style="font-weight: bold;">To:</span></b> historic@openstreetmap.org <br> <b><span style="font-weight: bold;">Sent:</span></b> Monday, January 21, 2013 8:32 PM<br> <b><span style="font-weight: bold;">Subject:</span></b> Re: [Historic] Temporal Tagging<br> </font> </div> <br>
<div id="yiv793738463"><div dir="ltr"><div class="yiv793738463gmail_extra"><span style="font-family: arial, sans-serif; font-size: 13px;">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:</span><div style="font-family: arial, sans-serif; font-size: 13px;">
<br></div><div style="font-family: arial, sans-serif; font-size: 13px;">1) Unlimited Changes to All Attributes: The schema should allow the recording of an <b>unlimited</b> number of changes to <b>any</b> 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.</div>
<div style="font-family: arial, sans-serif; font-size: 13px;">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.</div>
<div style="font-family: arial, sans-serif; font-size: 13px;">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.</div>
<div style="font-family: arial, sans-serif; font-size: 13px;"><br></div><div style="font-family: arial, sans-serif; font-size: 13px;">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.</div>
<div style="font-family: arial, sans-serif; font-size: 13px;"><br></div><div style="font-family: arial, sans-serif; font-size: 13px;">Brad Thompson</div><div style="font-family: arial, sans-serif; font-size: 13px;">Pastmapper</div></div>
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