[Tagging] is tourism a good category for everything cultural?

[Ross Scanlon]

On Tue, 24 Aug 2010 10:03:42 +0200
Ulf Lamping <ulf.lamping at googlemail.com> wrote:

> Am 24.08.2010 09:36, schrieb Ross Scanlon:
> >> Well, I will take a change to 'troll' again about it. This discussion
> >> comes up again and again because we don't have:
> >> a) clear tagging guidelines (*not* rules)
> >> b) mechanism to replace tags
> >
> > Agree totally.
> >
> > This (b) would be easily recitified by normalising the database in regards to tags.
> 
> So how do you easily: "normalise the mappers minds, renderers, editing 
> software in regards to tags"?!?
> 
> Over several years past now, I have seen this discussions come and go. 
> When someone was actually doing something, it usually ended up in a mess 
> of wiki, mappers, editors and renderers disagreeing how to tag 
> something. A confusion causing a *lot* more harm than any good.
> 
> It's simply a misconception, that just "cleaning up" the tag names will 
> lead to an easier mapping experience.
> 
> Regards, ULFL

You have no idea about normalising a database do you.


It has nothing to do with what you have above.


Rather than storing a tag as a key=value, you store it as a unique identifier.

The identifier is then referenced in another table in the database which will provide the key and value.


Lets take an example.


Currently in osm we have a road tagged with the following:

name="A street"
highway=residential
source=xyz


If the database was normalised then the following would occur.

name="A street"
tag_id=1000000
tag_id=1000001

The tagging table would have in it:

for a tag_id of 1000000

tag_id=1000000
key=highway
value=residential

for a tag_id of 1000001

tag_id=1000001
key=source
value=xyz


Now say that we decide that we no longer wish to call residential ways "residential" but a new name of "house streets".

To change the current database it would take a lot of effort but with a normalised database all we have to do is change the "value=residential" in the tagging database to "value=house_streets" and every way that was tagged residential is now tagged "house streets".


Tags like name would not have a tag_id as they are not unique.

The renderers would simply have to look in the tagging table to see what needs to be displayed.


-- 
Cheers
Ross