Here is more confusing goodness
I just read this at ibm developer works...
"if you're migrating from an EPUB 2 to EPUB 3 workflow, consider starting by converting from existing NCX documents. Because both input and output documents are XML, this is a perfect application for XSLT."
What in the world is XML and XSLT??
So now we have HTML, HTML5, XHTML, EPUB2, EPUB3, XML, and XSLT!
Sigh.
Carlos