I was just looking at a set of image files which are used to decorate custom form elements. I was analyzing how best to turn them into sprites1. One particular set of 3 images caused me to dream up a 'new' web standard: a resource tar.
The set was a left end-cap, a right end-cap, and a repeatable middle section to accommodate a control of fixed height but variable width. The end caps were say, 20px wide, but the repeatable middle section image was - and only needed to be - 1px wide. Now, if I were to combine the 3 in a stacked sprite, the 1px wide middle section would have to be stretched to the 20px width to match the end-caps. True, widening the middle section would compress well in PNG or GIF format - as it was destined to become -- but these were just 3 of the 20 or so images. I could make the tiny sacrifices along the way and probably create 7 sprites out of the 20 images .. but that's still 7 http requests.
Maybe right now you're thinking what I was - there should be a way to send all 7 at once. And if there was a way to do *that* - then why muss about with all this sprite nonsense at all2? Just leave the images alone in their 20 separate files, but send them all in one jar. It would be the browser's responsibility to interpret a jar file that came from "http://site.com/path/to/jars/jarfile.jar" and had an internal directory structure of
so that the images could be referenced in CSS as "http://site.com/path/to/jars/img/1.gif", "http://site.com/path/to/jars/img/2.gif"...
So what's with the title phrase "the new WAR"? Sending along the image assets for custom controls is just one application of this new "jar" or "war" file concept. Another is to send a packet that has the base images for a site: the logo and primary site decoration elements. Other people may conceive of other sets of resources that it make sense to combine and send along together in one packet.
1 For an excellent description of sprites, including some fantastic examples, see The Mystery Of CSS Sprites: Techniques, Tools And Tutorials.
2 Ok, the reason to still create the sprites is so that 'older' browsers - you know, the ones that don't have this as-yet unproposed feature - will still have 7 http requests instead of 20 (instead of the 1 they could have with this!)