How do I find out who deleted a relation?

You may be right. chipsterxx has been a member since Feb.2011. I'll need to know how to reverse that changeset and what it means for other edit within that said changeset. He'll probably ask me to do it for him and I have never done it before. There may be a language problem as well!

As far as "this tool" is concerned, I could not see how I could reincarnate the relation number.

If possible, it might be nice to avoid reverting the whole changeset, since there are v1 objects in there. It might be possible to use the RawEditor, but that takes a bit of practice (since you'd need to set the versions to what the API expects, and ensure that since-deleted ways no longer feature). There's also JOSM's revert plugin, which was much improved the last time that I used it, although (as with any revert operation) you'd need to be careful about exactly what you were reverting.

One thing that would also work would be to ask in one of the IRC channels (there's also a web interface if you don't have an IRC client to hand) - someone there would be able to help, I'm sure.

It is not going to be easy. chipsterxx has combined ways whereas only a portion of them belong to the relation. I do not have the required feelings like - "oh dear, something appears to have gone wrong" - It took me two weeks to walk this 120km (actually 240km walking distance) portion of the "Via Algarviana" with a drive of up to 1.5 hours to get there. How do I rate chipsterxx's contribution against mine? Are his v1 contributions worth more than the Via Algarviana relation? A continual influx of vibrant newbies, eagerly wanting to contribute, will always be a problem for the OSMF.

I have received a reply from chipsterxx and would like it to be generally known:

Dear dcp,

it appears you were upset that i deleted a part of your work on the Via Algarviana. Until your notice, i wasn’t aware such thing even happened. If i was actually the “perpetrator“, i duly apologize. It must have happened inadvertently, because i try to make sure no work by fellow mappers is damaged. From my own experience i know how much it takes to make these things happen and work. I spend endless hours at the computer trying to do as precise and accurate a job as possible.

Therefore, should that deletion be my fault, i apologize and would like to offer my help to restore the deleted relation to its former beauty.

I believe in cooperation, and therefore, especially in a project as complex and challenging as making a map of the world (or at least of the part of the world that concerns us), it is paramount that we work together as one.

Once again, dcp, let’s combine our efforts to make the best map possible! Tell me where work needs to be done and i’ll give my best effort to restore any lost relations.

It seems we are of the same breed: perfectionists. I suspect the mistake happened exactly because i perused an area that i perceived as less than precise and tweaked minor ways. So far i have no idea in what area said deletion took place. Maybe you can give me more info on that.

In any case, i’m sure together we will work it out. (And, as you can see, the language barrier really doesn’t exist!).

Sincerely, ChipsterXX