[Potlatch-dev] map_features.xml: <tag ... v="*">

[Steve Bennett]

Here's the question/issue I was trying to ask on IRC: what are the
plans for the v="*" attribute on <tag>, when it comes to creating an
object? My scenario:

1) Define a feature, traffic_calming, as follows:

 <feature name="Traffic calming">

    <category>transport</category>
    <icon image="icons/speed_hump.n.16.png"/>
    <help>
      http://wiki.openstreetmap.org/wiki/Key:traffic%3Dcalming
    </help>
    <point />
    <tag k="traffic_calming" v="*"/>
    <input type="choice" key="traffic_calming" name="Obstacle type"
category="Traffic calming" presence="onTagMatch">
      <choice value="yes" text="Unspecified"/>
      <choice value="bump" text="Short bump" description="A sharp
speed bump, typically slowing cars to 15 kph or less."/>
      <choice value="hump" text="Speed hump" description="A gentler,
longer bump, typically slowing cars to 30 kph or less."/>
...
    </input>

  </feature>

2) Instantiate it by dragging/dropping
3) Now we have an object with "traffic_calming=*" set literally.

In other words, the "*" works fine for matching, but it shouldn't be
used as a literal value when the object is created. Thus a way is
required to distinguish between the tags that are recognised as this
feature, and the tags that are created by default for this feature. I
was thinking maybe this:

<tag k="traffic_calming" v="*" default="yes" />

(create it with a value of "yes", but recognise any value)

or conversely:
<tag k="traffic_calming" v="yes" match="*" />

or much more powerfully, something like:
<tag k="traffic_calming" v="yes" />
<match>
  <tag k="traffic_calming" v="*" />
</match>

I notice that someone has apparently run into this issue with
building: if you create an area, and select Building > Building as the
feature, you get an object with a literal "building=*" tag.

Thinking a bit further ahead, has anyone thought about what to do when
two features coexist? A common situation (at least in my geographical
area) is something like "highway=tertiary;railway=tram". Should the
pane on the left be split horizontally, allowing multiple feature GUIs
to stack on top of each other...

(If I'm not using the terms feature, object, instantiate, tag, value
etc correctly, let me know so I can speak the same language...)

Steve