[Rebuild] About keeping and removing tags

Frederik Ramm frederik at remote.org
Fri Mar 2 17:53:05 GMT 2012


    my WTFE algorithm currently does this: "if the current version of 
the object has a tag with a key that was initially added by a decliner, 
then remove that tag".

This means that if a decliner added a "name" tag, with whatever value, 
then the "name" tag will be removed, even if it was subsequently changed.

The reason for this rather cautious approach is that I thought it is too 
difficult to determine whether the decliner's work was nullified by the 
later change, or built upon.


decliner adds "name=Pepe's"
agreeer changes to "name=Pepe's Pizza"

certainly we cannot say "the agreer has overwritten the decliner's 
contribution and we can keep the name" in this case.

In a recent discussion on talk-at, people were a bit unhappy about this, 
saying that even in cases where the name was clearly changed we'd be 
removing it, eg:

decliner adds "name=Hill Road"
agreer changes to "name=Blueberry Valley Drive"

They suggested that we use a more fine-grained approach that would 
somehow compare the strings, and only remove the name if the current 
version had sufficient similarity.

I think this is worth discussing.

There are other tags where the situation is just as difficult. If 
someone tags "addr:housenumber=45" and someone later changes that to 
"13" then the value 13 can hardly be a derived value but what if the 
original is 45 and the corrected version is 450?

There are also tags where the situation is much easier. For example, any 
change from one of the ~ 20 common "highway" values to another one of 
these values could surely be said to remove the original mapper's 
copyright on the highway type because changing that is hardly possible 
without first-hand information. Or is it?


Frederik Ramm  ##  eMail frederik at remote.org  ##  N49°00'09" E008°23'33"

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