KML file in Google Earth shows name of entity replacement - kml

Question

I've got a question referring to the BalloonStyle Tutorial in the KML documentiation:
BalloonStyle Documentation
Playing around with this KML file:
<kml xmlns="http://www.opengis.net/kml/2.2">
<Document>
<name>ExtendedData+SchemaData</name>
<open>1</open>
<!-- Create a balloon template referring to the user-defined type -->
<Style id="trailhead-balloon-template">
<BalloonStyle>
<text>
<![CDATA[
<h2>My favorite trails!</h2>
<br/><br/>
The $[TrailHeadType/TrailHeadName/displayName] is <i>$[TrailHeadType/TrailHeadName]</i>.
The trail is $[TrailHeadType/TrailLength] miles. <br/>
The climb is $[TrailHeadType/ElevationGain] meters. <br/><br/>
]]>
</text>
</BalloonStyle>
</Style>
<!-- Declare the type "TrailHeadType" with 3 fields -->
<Schema name="TrailHeadType" id="TrailHeadTypeId">
<SimpleField type="string" name="TrailHeadName">
<displayName><![CDATA[<b>Trail Head Name</b>]]></displayName>
</SimpleField>
<SimpleField type="double" name="TrailLength">
<displayName><![CDATA[<i>The length in miles</i>]]></displayName>
</SimpleField>
<SimpleField type="int" name="ElevationGain">
<displayName><![CDATA[<i>change in altitude</i>]]></displayName>
</SimpleField>
</Schema>
<!-- Instantiate some Placemarks extended with TrailHeadType fields -->
<Placemark>
<name>Easy trail</name>
<styleUrl>#trailhead-balloon-template</styleUrl>
<ExtendedData>
<SchemaData schemaUrl="#TrailHeadTypeId">
<SimpleData name="TrailHeadName">Pi in the sky</SimpleData>
<SimpleData name="TrailLength">3.14159</SimpleData>
<SimpleData name="ElevationGain">10</SimpleData>
</SchemaData>
</ExtendedData>
<Point>
<coordinates>-122.000,37.002</coordinates>
</Point>
</Placemark>
<Placemark>
<name>Difficult trail</name>
<styleUrl>#trailhead-balloon-template</styleUrl>
<ExtendedData>
<SchemaData schemaUrl="#TrailHeadTypeId">
<SimpleData name="TrailHeadName">Mount Everest</SimpleData>
<SimpleData name="TrailLength">347.45</SimpleData>
<SimpleData name="ElevationGain">10000</SimpleData>
</SchemaData>
</ExtendedData>
<Point>
<coordinates>-121.998,37.0078</coordinates>
</Point>
</Placemark>
</Document>
</kml>
When you remove one of the SimpleData elements, Google Earth shows the Entity Replacement from the Balloon Template. For example you remove the line <SimpleData name="ElevationGain">10000</SimpleData>
it shows up in the Balloon like "The climb is $[TrailHeadType/ElevationGain] meters." Which doesn't look very nice.
Any idea how to tell Google Earth, that it shouldn't display the line from the balloon, if there is a missing SimpleData?
Thanks in Advance

Answer 1

I don't think* you can do what you are asking here - i.e. apply conditional logic within this style text. I have had a similar requirement in the past (certain pieces of data were missing from some of my placemarks) and I ended up applying different styles for each of the possible scenarios of missing information when generating the KML.
It felt both very clunky and if you have a large number of scenarios of one or more items being missing while others exist it could quickly be a mess.
*Would love to be wrong.
UPDATE
Just looked at my code for this, and I actually ended up putting all the text in the placemark fields of my schema, and printing out empty nodes when I did not have data - also less elegant, but did not require additional styles in the end. Based on your example something like:
<BalloonStyle>
<text>
<![CDATA[
<h2>My favorite trails!</h2>
$[TrailHeadType/TrailHeadName/displayName]
$[TrailHeadType/TrailLengthBalloonText]
$[TrailHeadType/ElevationGainBalloonText]
]]>
</text>
</BalloonStyle>
<Placemark>
<name>Difficult trail</name>
<styleUrl>#trailhead-balloon-template</styleUrl>
<ExtendedData>
<SchemaData schemaUrl="#TrailHeadTypeId">
<SimpleData name="TrailHeadName">Mount Everest</SimpleData>
<SimpleData name="TrailLength">347.45</SimpleData>
<SimpleData name="ElevationGain">10000</SimpleData>
<SimpleData name="TrailHeadNameBalloonText"><![CDATA[The trail name is Mount Everest</br>]]></SimpleData>
<SimpleData name="TrailLengthBalloonText"><![CDATA[The trail is 347.45 miles.</br>]]></SimpleData>
<SimpleData name="ElevationGainBalloonText"><![CDATA[The climb is 10000 meters.</br>]]></SimpleData>
</SchemaData>
</ExtendedData>
<Point>
<coordinates>-121.998,37.0078</coordinates>
</Point>
</Placemark>
Then when you have no data you leave that item blank:
<Placemark>
<name>Difficult trail</name>
<styleUrl>#trailhead-balloon-template</styleUrl>
<ExtendedData>
<SchemaData schemaUrl="#TrailHeadTypeId">
<SimpleData name="TrailHeadName">Mount Everest</SimpleData>
<SimpleData name="TrailLength">347.45</SimpleData>
<SimpleData name="ElevationGain">10000</SimpleData>
<SimpleData name="TrailHeadNameBalloonText"><![CDATA[The trail name is Mount Everest</br>]]></SimpleData>
<SimpleData name="TrailLengthBalloonText"></SimpleData>
<SimpleData name="ElevationGainBalloonText"></SimpleData>
</SchemaData>
</ExtendedData>
<Point>
<coordinates>-121.998,37.0078</coordinates>
</Point>
</Placemark>

Answer 2

As my data are changing somehow quite often, I'm now providing a xml file linked to an css file and embed it as an iframe in the description. For offline use, create a kmz and put the xml and css into it.
For a small tutorial have a look here:
http://www.w3schools.com/xml/xml_display.asp
In the kml, it looks as follows:
<description>
<![CDATA[
<iframe src="http://www.w3schools.com/xml/cd_catalog_with_css.xml"></iframe>
]]>
</description>