Around the year 1999, I was talking with a potential investor about the marvels of markup and the implications for the world of GIS and the World Wide Web. I scribbled on the paper something like:
The investor looked at me with dubious smile. Later that day I tried my wife, who told me I should focus on something useful. In spite of these early negative experiences we persevered and finally (in 2000) there was GML. Neither the investor, nor my wife were any more impressed. Nonetheless GML development continued. Fast forward to 2005. My wife calls to tell me to look at Google Earth – it was apparently "revolutionary". Later that day I encounter that same investor with the same "look at Google Earth" mantra. I was intrigued to say the least. So I did. Impressed, I looked below the surface and read the KML tutorial (and later the KML reference guide at http://www.keyhole.com/kml/kml_doc.html ), What did I find?
As a looked further I realized that the entire geometry model of KML – this revolution of 2005, was an idetic copy of the geometry model of GML v1.0. Other parts of Google KML are snippets (identical) to parts of GML 3. (e.g. TimePosition etc.). Still further I noted that KML had introduced application schemas, not by using XML Schema as in GML, but by introducing a new schema language (as was tried an abandoned in GML v1.0).Â So is this a revolution or not? If so what is the revolutionary part of it? Is it all just timing?
After some thought I have decided that this is indeed a revolution and for many of the same reasons that drove my thinking in 2000. But before we get to that – why the success of Google Earth thus far? It surely is not just because of markup?
I think the success of Google hinges on a few things – most of which are not really connected with markup.
- It provides global coverage of the earth using both maps and satellite inages. I think this is the biggest single factor.
- It provides a slick user interface.
- It enables you to place your information (Placemarks) on the map (here markup IS USED).
- It allows your information (your placemarks) to be fetched from a remote site.
- It provides a single engine that takes your information, styles it and presents it on their site. It is in effect a single, geographic application.
So where is the revolution? I think there are several parts to the answer.
- Google Earth is revolutionary because it brought an awareness of the accessibility and utility of geographic information to a wide commercial audience.
- By providing an integrated publishing site – in our terms a style engine and a backround map server with global coverage – it allowed people to create simple markup that DID something – i.e. they could see it visualized in a meaningful context on their screen.
Google Earth illustrates the power of dynamic geographic data publication. This is for me the real revolution – the one we dreamed about back in 1999. Here we have the first signs of life. From here the way forward seems more well defined.