[Tagging] Feature Proposal - RFC - sluice_gate

[Paul Norman]

> From: Steve Bennett
> 
>   On 5/01/2011 3:18 PM, John Smith wrote:
> > Perhaps a more generic approach would work, eg waterway=flow_control
> > flow_control=weir|sluice_gate|flood_gate|spillway_gate|....
> Yeah something like that would be reasonable. What I'd like to see a lot
> more of is planning ahead: coming up with a scheme into which all future
> subtags can be slotted. It's very hard to change a tag once it's become
> popular. So perhaps:
> 
> waterway=dam (a wall with water on one side) waterway=weir (a wall with
> water flowing over the top) waterway=flow_control (an opening through
> which water sometimes flows).
> flow_control=sluice_gate|flood_gate|spillway_gate|lock_gate...
> 
> Then we get people who know this stuff to try and find exceptions that
> don't fit into the above scheme, and redesign it.
> 

I've been looking into this. How does this sound?
waterway=dam and waterway=weir remain unchanged. 

waterway=flow_control - a device for controlling the flow of water

flow_control=sluice_gate|discharge|...

sluice_gate: a sluice gate.

discharge: A discharge point like
http://en.wikipedia.org/wiki/File:Howell-Bunger_valve.jpg

The question is, what else would go there? Flood gates don't belong there -
that's the *usage* of the gate, not the *type* of gate.