RFC: MetaWeblog API. "It's time to broaden the XML-RPC pipe that tools use to connect to Radio, and in doing so offer an evolution to the art of scripting weblog tools." [Scripting News]

To add a sprinkle of the semantic web to the api: Instead of the postid, use permalinks. The cool thing is that permalinks are globally unique. So maybe you could call getPost to a community server, which knows where to get the posts. And an edit tool using the api can provide a link to the online version of the post. Blogid could also be changed to the home url of the blog, but I'm not yet sure if that will actually help, or if it is possible for every blogging software.

To clarify my previous post, I made a little demo that transforms OPML to XML. You can see how you can add opml:text and xlink:href attributes to any XML file. Note that OPML is just fine. It's just me enjoying the exploration of theoretical alternatives.