[josm-dev] Another 66 relations bite the dust

[Sebastian Klein]

Richard Fairhurst wrote:
> But it appears to be a similar issue to these postings which posit 
> possible causes:
>    http://lists.openstreetmap.org/pipermail/josm-dev/2010-April/004276.html
>  
> http://lists.openstreetmap.org/pipermail/talk-gb/2010-February/005359.html

The first two links refer to the problem that a conflict on relations 
can easily lead to removal of all members, so I guess it's a different 
topic.

> http://lists.openstreetmap.org/pipermail/talk-gb/2010-February/005363.html
>  
> http://lists.openstreetmap.org/pipermail/talk-gb/2010-February/005368.html

These posts describe a well known problem [1], but no one came up with a 
solution for it so far. With the current API it seems to be practically 
impossible to have a complete list of referrers for all the objects in 
the data set. This causes holes in route relations, but it shouldn't be 
a 'relation killer'.

> FWIW I suspect it isn't a _bug_ as such, but rather that the UI is 
> unclear (at least to novice users) such that it is too easy for the user 
> to mistakenly delete/blank the relations. Again, deleting many (66) 
> relations that you haven't intentionally touched, or entirely deleting 
> large (893-member) relations, is likely to be an error in most 
> circumstances: the user should be made aware of what they're doing in 
> terms they are likely to understand.

Without good user feedback it's not easy to remove these traps.

But anyway, it shouldn't hurt to add some heuristics that detect unusual 
pattern (like deleting a whole bunch of large relations) and give a 
second warning before upload.


Sebastian

[1] http://trac.openstreetmap.org/ticket/2652