[OSM-talk] Historical Data in OSM database

[Laurence Penney]

On 10 Nov 2010, at 23:31, David Murn wrote:
> Just out of interest, are you 100% against OSM keeping recent history
> data?  If a building is demolished, do you believe that deleting the way
> should remove any trace of that from OSM, or do you believe that OSM
> should retain a history?

Of course the history trace is a very valuable thing about OSM. By contrast, adding things which don't exist any more - mapping the past - is, as Richard Weait says, orthogonal to OSM.

> How long should that history be retained? In 10 years, would you advocate that any historic data (objects deleted over n years ago) be deleted, to avoid cluttering the database?  If OSM had existed 20 years ago, would you be advocating that the database be kept clean, so that only current data is in it?

As with any wiki, keep all the edits you can until they overwhelm you.

It's not a question of how long to retain edits. I'm no backup expert. FWIW I don't think it's vital that every transformation to every entity in OSM is kept forever. I have no idea how much of a burden it is to the db admins to maintain the history, nor what their projections are for the situation 20 years hence. A proposal that involved selective forgetting of edits would surely be far more subtle and respectful than dumping based merely on age.

> OSM, by its nature, is excellent for retaining historic data, for
> example if a road is realigned, you have a history that shows how it was
> realigned, or if a road changes name, there exists a history of previous
> names.

Yes, that's a fantastic thing about OSM.

>> I'm not sure what you're saying - that 18,000 tag usages is
>> insufficient for someone to try to sort out a mess of tag values?
> 
> I read it more as 'this tag already has a range of values and other
> uses, do you really have to use it?'.  You also have to wonder, of those
> 18,000 tags, how many are in your area of interest, and what percentage
> of nodes in that area are tagged?  Maybe .1% if youve been busy.

I understood the tag was started by Frankie Roberto who was specifically interested in adding historic data to OSM. Whether most people are using it in the way he hoped I do not know. What's the relevance of my "area of interest"? Most of the edits there are "(big)", performed by bots whose authors have determined that a tag is being used incorrectly without asking me or other Bristolians. They seem to be doing a good job.

- L