That's simple; there is no common format today. If the OS manufacturer doesn't set an example why should anyone else.BHpaddock said:What's stopping Outlook and Sunbird from using a common format today?umerh said:*snip*
Nothing. Except the same thing that would stop them from using a common schema in WinFS.
However if there had been a WinFS common object format, with scope for extensibility then you may well have seen it used.