A brilliant note from Rick Jelliffe of Topologi, on the subject of W3C XML Schemas, from which I excerpt: Any sufficiently monolithic technology is indistinguishable from spaghetti. Once a large technology is made from sufficiently intertwined parts, there is no way to order an exposition of it such that strongly-connected ideas are always close together. Spaghetti doesn't want to be free. (At least, "no way" to order the exposition with HTML-style pages: maybe WXS needs something more like Nelson's transclusion, where you can pull in fragments (without losing their context) and embed them into running text, without the maintenance penalty of duplicated sections.) Indeed, I think that is a forgotten rationale for XML over SGML: dumbing down an intertwined technology so that it could have a spec straightforward-enough that people could conveniently read it.
