It was suggested that I add this following background comment: I've been a Mathematica user since version 2. I have even written to Stephen Wolfram suggesting a front-end supporting my vision. I love Mathematica, and do not wish to disparage it, but it is not an ideal authoring tool for my purposes. All of my daily study note live in Mathematica notebooks, but, on those rare occasions in which I wish to produce a traditionally structured mathematical document, I use LyX.
I have a long-standing dream of producing object-oriented mathematical documentation using XML. This might be a combination of customized DocBook and MathML. Creating such a documentation system would include both defining document types and having a reasonably usable editor which would allow the author to focus primarily on the mathematical and verbal content, not on the details of the underlying XML representation.
Having an editor which supports the creation of well-disciplined XML documents with MathML support, including a usable equation editor, would be a huge step in that direction. Is there a WYSIWYM editor which supports the production of, say, clean xhtml/MathML documents? I am particularly interested in open source, though proprietary system are also of interest.
If you are familiar with LyX which produces LaTeX documents, that will give you a good idea of the kind of interactivity I am seeking.
As a motivation for how we might use such a documentation system, consider how we might represent a theorem. We create a <theorem\>...content...</theorem> element which could include such elements as <dependencies/> which would be all theorems, definitions, etc. needed to prove the theorem. There would be an element for the statement of the theorem, as well as an element for the proof of the theorem. At those points in the theorem where some precursor element is referred to, we could display a numbered reference with a mouse-over and hyperlink to that element.
It would be very easy to process such a document to produce a derivative document listing only the theorem statement, without the proofs. Chapter, section, equation, definition, theorem, etc., numbering would be automatic. Index entries could be tracked using attribute tags.
The font-face and decoration of mathematical symbols could be determined by style sheets. For example, we might want vectors to appear in bold-faced Latin in one context, but with an over-arrow in another. The document would not have to be rewritten in order to effect that change. It would be accomplished globally by changing the style sheet.