When Microsoft says the next version of Office is its most important revision in over a decade, it’s not kidding. New XML-based default file formats and a major interface revision are intended to make the market-dominating productivity suite more flexible and accessible than ever … But lurking behind the scenes is a change that may ultimately prove even more significant than the interface makeover: Microsoft’s replacement of its current proprietary default file formats (.doc, .xls, .ppt, and so on) with new compressed XML-based file formats, denoted by the addition of the letter x to the traditional file extensions.

