How should NASA's World Wind handle the introduction of a shapefile layer? Well, I can think of two reasonable ways to do this.
- somewhere there exists a .zip file containing the three component files of the shapefile. A third party has written an XML which describes how they want that shapefile drawn (e.g. with and without labels). Their XML file specifies the URL of the shapefile.
- somebody wants to publish a shapefile directly usable by WW. They
create the .zip with the three shapefile files, and add to it the .xml
needed by WW.
I can think of only one benefit to #2: you don't have to deal with telling your webserver that a .xml file is an XML file rather than some kind of mutant HTML. A big advantage of #1 is that anybody can describe anybody else's file for use in WW, *and* they don't have to host that shapefile.
We could support both formats, of course. If you tell WW to use a shapefile, WW could look at the filetype / extension. If it's XML, then the XML specifies the shapefile with a URL. If it's .zip, then the .zip contains the XML file.
Now, the second question is how to handle versions. Is there any reason to keep permanently a shapefile given that WW doesn't permanently keep any imagery data? Basically, WW is an online data viewer and only caches imagery data. Why should it save a shapefile? Thus, whenever you turn on a shapefile, WW should re-fetch the shapefile (checking the HEAD just as a web browser does). If somebody *really* wants to display local data, they can specify file:// as the URL.