After some useful comments on my last post on the subject, and having emailed Jeremy Keith, who spoke about microformats at SxSW, I've thought about the ancestor microformat some more.
Jeremy suggested that amalgamating several microformats together should probably be called a macroformat, and although he didn't say as much, I think maybe my idea wasn't such a good one.
Until I decide how to proceed properly, I've added an hCalendar event to each grave where dates are visible; the event is basically the person's life, with birth being the "from" date, and death being the "to" date. Here's an example, which is picked up by the Tails Firefox extension.
It's not ideal, but it's a start.
[Tags: microformats genealogy jeremykeith macroformats hCalendar]