[OSM-talk] Potlatch and the evil semicolons

[Mark Williams]

Dermot McNally wrote:
> 2008/5/27 Rory McCann <rory at technomancy.org>:
>> There's a FAQ entry that says that you should use ";" as a value separator
>> (http://wiki.openstreetmap.org/index.php/Faq#What_shall_I_do_for_roads_that_have_multiple_values_for_a_tag.3F).
>> Is this offical OSM policy? If so then, merging ways this way seems like The
>> Right Thing for potlatch to do. Sounds like some renderers can't cope with
>> this. Isn't that a renderer flaw?
> 
> Well...
> 
> Let's start with the simple part. A road is either primary or
> secondary, not both. So while a semicolon might be an interesting way
> to tag such a shared identity, in the real world you won't ever want
> to do so. Predictably, the renderer requires you to commit to one or
> the other, so a semicolon here can be considered breakage.
> 
> I'm going to claim that the same holds true for name. When merging
> ways, a name conflict generally means you shouldn't have merged them.
> In Dublin, there's a long stretch of road that is variously George's
> Street, Aungier Street, Wexford Street and a bunch of others. Merge
> the wrong two ways and you'll end up with both, split by semicolon.
> Once again, there's no good use this could be put to. There is a real
> edge case here, though, such as where you may have "Wibble Terrace"
> sitting on "Foobar Street", wholly contained within it. I've seen
> other discussions on that, but can't see that a semicolon will solve
> the problem.
> 
> Road ref begins to enter the territory where you might consider a
> standard way of handling multi-valued keys. Not all countries support
> multiplexing, but those that do could make use of this. This was the
> possible valid case I had in mind for what Potlatch is doing, but TBH,
> it feels more like something a mapper should have to consciously set.
> Helpfully combining existing values seems a bit wrong.
> 

I too have had to go back & fix several of these concatenations, mostly
in names of roads, where someone has come into a 'done' area with
Potlatch & 'prettified' roads - mostly just doing what bezier hinting
does, but sometimes bollixing things up. There are a number of roads
round my way with London Road ; Tank Hill Road ;  etc type errors - I'm
getting through them... I hadn't realised that's a Potlatch thing
though, I'd just assumed he was a prat.

I'd ask the user but I think he's done round here & wandered off to
bugger somewhere else up now.

It might help if [these people] filled in a bit on their user pages so
we have some idea if it's a local newbie or a vagrant pest?

Mark