[Openstreetmap-dev] Strange data allowed?

[Immanuel Scholz]

Hi,


>> > > - tracks without any line segments
>> > no, it shouldn't
>> So as Frank asked already: What to do if you delete the last segment
>> from a track.
> The last segment from a street? The street doesn't get shown any more,
> but it's still there to get back if you want.

Then why do you reject the import of an empty track? If a track is legal,
you can allow users to import them. Or else the user could start importing
tracks with dummy segments that get deleted just after import.

I don't know why an user may want to import empty tracks, but I don't
think you should putting him stones on his path he can easily jump over.

Maybe if you first specify all bus routes, and then starting assigning
segments to them or wait for others to assign their bus stops...? ;-)


> It works the same way if you remove a node from a segment.

Second... you can remove a node from a segment? What should that look
like? Segments must have 2 nodes all the time, so what does the server do
if you delete a node from a segment?


>> > > - line segments that are not part of tracks (not possible in GPX)
>> > no
>>
>> So this means, if the user delete a track, all line segments that are
>> not part of any other track are deleted as well? Then similar problem as
>> above (deleting the last line segment of a track) happen.
>
> The street is just a set of segments. Deleting the street drops the
> relation between the segments, it doesn't delete the segments themselves

So same problem as above. If you want to have some segments without tracks
in the server, you have to upload a dummy track and then delete that
track.



>> > > - areas with fewer than 3 points
>> > no
>> Then the problem "deleting anything from anything" occours.
> Not sure what you mean.

- If you allow an user to delete a node from an area with only 3 nodes
left, then you can allow him to upload 2-node-areas as well.
- If you auto-delete the malformed area after the user deletes one node of
a 3-node-area, then you complicate things like reassigning nodes.
- You could disallow the deletion of a node from an 3-node-area. ("Node is
used. Please delete the area 'Central Park' first.")


> You see, all the data is wiki'd so it's all still there to get back.

The bookkeeping of the wiki is not for general edit purpose.

I think, if a client has to revive an object from the wiki's history
automatically in its normal working progress, something is wrong.

But since you tend to tolerate malformed objects in the database, this is
no problem anymore. If nothing gets deleted automatically, the clients
don't need to automatically revive anything ;-)



> I used to work writing polyhedra software and there are people on this
> list with better computational geometry skills than me.

Cool, so I can close this problem. Then I'll stea..., err, inspire your
area checking code for JOSM later then ;-)


Ciao, Imi.