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Hi Jason, The difference is: a mobile sitemap is a sitemap showing the URLs of your separate mobile pages. the mobile annotation you mentioned above, for the regular desktop sitemap, is just a way of indicating that there is an alternate version of the desktop page for mobile users (it's basically serving the same purpose as the rel=alternate 'switchboard' tags that go in the desktop page's HTML). You would still need to include the rel=canonical switchboard tag annotation in the mobile page's HTML. Hope that helps!

Hi Jason - we do have some continual improvement plans for OSE and for our metrics. Obviously, the Just Discovered links feature was one of the most recent and valuable ones. We also do refactor and recalculate Page Authority/Domain Authority on a regular basis to make them better correlated with changes to Google. On the longer-term horizon, we're planning a webspam metric, and we may be using more data from social and fresh web to improve PA/DA.