Wednesday, February 01, 2006

What's the big deal about KML format?

Looking over some different blog posts about the wonders of the KML format, I am left scratching my head as to what is so great about it. Certainly, it is nice to have a way to specify certain geospatial features, camera values, overlays, etc.. along with network links to other information in the same file in XML format. But each of these features are pretty obvious in themselves.

It's always the user interface that is the make or break issue of any software application. KML is pretty good at specifying what you are going to see and from where you will be looking. However, there is a disconnect in how this information is used by the underlying graphics engine and how those files and their contents can be managed and manipulated by the interface. The My Places/Temporary Places link area is very klunky and limited in my opinion.

As a format, GML is more precise and complete and would be a better basis for a feature format. One is a very nice number, having all of the information you need in a single file is very compelling from a standpoint of simplicity. The network link allows data from various sources to be cobbled together, very powerful, just like HTML. Could this be improved upon?

The idea I have for EarthBrowser is of a self contained data package that contains different elements such as features, camera settings, overlays, image files of various formats, shapefiles, engine scripts in separate files (or together if it makes sense) all packaged together in a zip file (or my favorite a bzip2'ed tar file). This reduces the number of network connections needed, consolidates the data so you won't have a situation where a critical part of the data is missing due to a download failure and eliminates the program states where only partial data is available. The engine script can use the a pre-existing user interface system to decide how it will display itself in the interface. For very large data packages, it becomes feasable to share them as a .torrent file amongst other EarthBrowser users, reducing the server load for popular packages and improving availability for end-users. One negative is that since you need the whole package, there is no way to display information as it arrives like a web page. However for 3D environments it may not make much sense, or be possible, to display partial information like HTML.

4 comments:

Anonymous said...

I think the "big deal" about KML is that it is easy for beginners and well publicized. You have tons of people building KML files who never knew such things existed before Google released Google Earth. It has to do more with "how to get new users involved quickly" and eventually those people may get to the point where they migrate to other formats.

matt_giger said...

Hmmm. Well there is certainly a lot to say about simplicity for the users being pretty much *the* big issue for most software. I guess my point was that the KML format, by itself, is not at all revolutionary or even inspired. The concepts that can be represented in it are widely known and available elsewhere.

It's seems similar to the way people went "ga ga" over HTML in the 90s, even with all of it's shortcomings. It's just the standard format for the "it" program and people feel empowered to be able to generate content on it and make the computer do what they want. I suppose I don't get the same feeling of empowerment from doing scripting since I mostly get that from C++.

Thanks for the perspective.

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