Developments in Open Source Textbooks: mathbook XML

Rob Beezer at University of Puget Sound is spearheading the development of MathBook XML, which is "a lightweight XML application for authors of scientific articles, textbooks and monographs."  I'm seriously considering a conversion from Mathematica Notebooks to this new format. I spend a bit of time playing with the current version this week and converted a very small web page with a few sage cells. Then I exported to html. It wasn't obvious to me what code should appear in the output field of the sage sections, which would be all graphics in this case.  It isn't a problem for the html version since the cells can be evaluated.  Converted to LaTeX, the lack of output is a problem, but it still looks good.