[OSM-dev] Chopped of ways. New flag for OSM XML?

80n 80n80n at gmail.com
Tue Aug 12 17:56:14 BST 2008


On Tue, Aug 12, 2008 at 4:41 PM, Karl Newman <siliconfiend at gmail.com> wrote:

> On Tue, Aug 12, 2008 at 6:50 AM, Jochen Topf <jochen at remote.org> wrote:
>
>> Hi!
>>
>> When creating excerpts of OSM data with Osmosis, Osmosis will (depending
>> on flags) chop of ways, i.e. the output will contain ways with only some
>> of the nodes in the way. But looking at the XML there is no way to tell
>> that this has happened. The way still has the same ID and timestamp.
>> There should be a way of recognizing theses chopped of ways, say by
>> adding an incomplete="true" attribute or something.
>>
>> This question came up on the German mailing list after somebody had used
>> the excerpt as basis for some automated fixing of data. He (IMHO
>> correctly)
>> checked the Osmosis excerpt with current data from the API by comparing
>> the timestamps which were the same. So he assumed nothing had changed
>> and he could safely edit the data. But because of the excerpt process
>> the data he based his decision on, was not correct.
>>
>> This is part of a larger problem. Say you create an extract with only
>> some of the tags or a relation with only some members.
>>
>> Jochen
>>
>
> How about osmosis:mangled=yes? Or what about touching the timestamp of the
> entity?
>

I agree that some kind of attribute would be very useful to indicate that
the data is not complete in this case.  However, I don't think it should be
an osmosis specific one.  So mangled='yes' rather than
osmosis:mangled='yes'.

There could well be other data sources that mangle data, and having to check
all the different possible namespaces would be infeasible:

  osmosis:mangled='yes'
  osmxapi:truncated='1'
  someOtherSource:complete='no'
  etc

The core osm xml schema needs a documented attribute that can be used to
indicate that the data is incomplete.

This can be done immediately as there is no need for any changes to the API,
by definition it currently always returns complete data.  However it would
be nice if some future version of the API were to block any uploads that had
a complete='no' attribute on any element.

(For the sake of clarity, I'm talking about an XML attribute here, not some
additional <tag> entry like <tag k='osmosis:mangled' v='yes'/> which
wouldn't help as it would just end up in someone's database :S ).

80n


>
> Karl
>
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