On Mon, May 13, 2013 at 7:58 AM, Steve Bennett <stevag...@gmail.com> wrote:
> On Fri, May 10, 2013 at 8:24 PM, Richard Fairhurst <rich...@systemed.net>
> wrote:
>
> > So for the tiny number of renderers/routers which want to show bridge
> types
> > differently - and my canal renderer will be one of them! -
> differentiating
> > based on a single bridge= tag is plenty easy enough. For the majority of
> > renderers/routers, "it's a bridge" will suffice.
>
> In this case, "movable" is such an obvious place to break the
> hierarchy down. It's very easy to imagine a non-specialist map would
> want to show movable bridges slightly differently. It's much harder to
> imagine many maps caring about the difference between bascules and
> drawbridges.
>
Agreed.
> Similarly, the bridge_type=* is a convenient place to get all the
> bridge nerdery out of the way of normal data consumers. (But I'd
> quibble: I'd promote "floating" and "culvert" as a fundamental kind of
> bridge, and demote "trestle" and "cantilever" as bridge_types).
Well, bridge_type or bridge:structure or whatever isn't *just* for
offloading technical detail of limited rendering value; it's also a
conflict-prevention measure. Demoting "cantilever" into that key, for
instance, makes it impossible to express both "cantilever" and "truss"
simultaneously, which presents a problem. Now, I've realized that
"bridge=covered" is actually superfluous to "bridge=yes; covered=yes"; if
that goes away, several of the values ("trestle", "viaduct", "movable",
"cantilever") sort of have a loose association in describing how the spans
are supported or mounted. So promoting "floating" up there would make sense
to me, but I wouldn't demote "cantilever" and I'm inclined to keep
"trestle" together with the nearly synonymous "viaduct".
Because it's almost always tagged on the lower, rather than the upper, way,
I'm inclined to drop "culvert" entirely barring a strong argument to keep
it.
--
Chris Hoess
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