Welcome to the SWX discussion and support group/list.

SWX is the native data format for Flash. Data is stored as SWF bytecode (you can't get more native than that on the Flash Platform) that is interpreted by the Flash Player. The SWX format is a subset of the SWF format (just like JSON is a subset of JavaScript).

More information about SWX can be found at http://code.google.com/p/swx-format/.