I received an email from Ian Griffiths who informed me that the "Xaml spec refers to Xaml as Xaml, and not XAML." because Rob Relyea didn't like the "shouty caps" look of all upper case.
After some back and forth, I contacted Rob, who wrote back that Ian is right (no surprise there) but that Rob is "…starting to use XAML" as that ship has sailed.
I don't know, Rob is pretty amazing, (the image below is a link to his blog), and I'm inclined to agree with him that Xaml is a lot classier looking than XAML.
I suggested that I would put the following note in Programming Silverlight
A quick note on the capitalization of Xaml. Ian Griffiths (who truly knows everything) sent an email that Rob Relyea submitted the official specification with the capitalization as Xaml rather than XAML. While even Rob agrees that all upper case is the popular usage, his blog, Xamlified (http://tinyurl.com/6h6rr5) is an oasis of camel case, and high quality information. This book will use both capitalizations for the sake of inconsistency.
Maybe we can start a movement. I'm going to try. If nothing else, this discussion has led me to find YAAM (Yet Another Amazing Microsoftie) which makes it worthwhile. Keep an eye on his blog; there are gems there.
For those of you about to write that this is a trivial and meaningless distinction not worth the time to blog about… I pretty much agree.