[OSM-talk] Suggestion: fallback tag

[Steve Bennett]

On Fri, Dec 18, 2009 at 6:16 AM, Tobias Knerr <osm at tobias-knerr.de> wrote:

> that, and that would be appropriate for reserves, too. But some other
> renderer might write "park" all over the area or do something else that
> makes the rendering completely inappropriate for the feature. What if I
> use "beach" as the fallback for my golf bunkers and get ice cone and
> beach ball icons, rather than the yellow area I had expected?
>
> Another problem with your approach is that it only works in renderers
> designed with the intention to display /everything/. I'd expect good
> rendering styles to be limited to a selected subset of the available
> information.
>
>
Two good arguments against my proposal.

Richard Fairhurst wrote:
>This is just redundancy on a massive, massive scale. You're inserting the
>same "hint" millions of times when you should be inserting it once. If
>landuse=park always approximates to leisure=park, then that either needs to
>be in the renderer stylesheets themselves (and it'd be one line in the
>Mapnik stylesheet or osm2pgsql setup), or in a general equivalence document
>that all the renderers can use (Shalabh's tree thingy).

>Rendering information, of any stripe, does not go in the database. That is
>absolute.

More good points.

>So the right way to solve it is to lower the barrier to getting Your
>Favourite Feature rendered. Fortunately this is happening.

Yes. Rather than the right way to solve it being, say, "do what the rest of
us do, install mapnik and start hacking on stylesheets".


>Cartagen is an instant-gratification JavaScript renderer. It's awesome.
>Halcyon is the Flash one I'm working on and if you'll permit the immodesty,
>I'd say it's ok, too.

I wouldn't say it's ok, I'd say it's great - even at this early stage. Very,
very cool indeed. And it totally works for reducing the barrier to entry for
tweaking rendering: I already used it to demonstrate a proposal for divided
ways.

However, by "instant gratification", I don't just mean "I get to see, on my
desktop, the map rendered how I want". I mean, "I get to know that
*everyone* will see the map rendered nicely".

I was thinking last night that there are four different goals/approaches
that one could be heading for in helping OSM:

1) Doing stuff that helps you directly. For example, tweaking a stylesheet
to render a map for yourself, adding tags that are only meaningful to you.
2) Doing stuff that helps others directly. For example, mapping a new area
in a standard way, adding styles to a standard stylesheet.
3) Doing stuff that helps others to help themselves. For example,
documenting ways to install the software, adding renderer support for
obscure tags.
4) Doing stuff that helps others to do things of benefit to others. For
example, working on improving processes, documenting tags, trying to
increase compatibility between renderers etc.

Some of the solutions proposed in this thread were essentially 1. Whereas
I'm mostly interested in 4 - it's just what motivates me. Getting a nicely
rendered map is nice. But multiplying that up, so that everyone is helping
everyone get nicely rendered maps - that's what motivates me.


>This leads to a virtuous circle: one renderer supports the tag -> tag more
>widely used -> more renderer support -> and so on.

Yeah, I'm still exploring this circle and looking at ways it can be
improved. Maybe it can be made more efficient, maybe it can happen with less
mistakes, maybe it can happen faster...etc. Better feedback in both
directions will help.

>Andy first started
>rendering ncn_ref on OpenCycleMap several years ago, when OCM was just a
>little local project rather than the world-conquering behemoth it is today.
>Now there are cycle renderers for local areas, for Garmins, for routing,
and
>so on. It really works.

Yeah, cloudmade routing is awesome.

So, thanks Tobias and Richard for very constructive responses which convince
me that my proposed fallback:* tag is too much of a hack to be worth
pursuing. I'll keep investigating the idea of a centralised rules table
though.

Steve
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