Re: Loss of information going from SGML to XML
Yes XML isn't full SGML but that is by design not accident. While we have lost "expressive" power, like being able to omit tags, we have something that itself is far simpler to express and will make it possible for information delivered over the web to "express" itself. This is what we should focus on not bemoaning the fact that "information" is lost in a "down translation" from SGML.
XML *is* SGML. No down translation required - as long as you stay within the lines.
If you can't live without the great intricacies of SGML, tar, gzip, and ftp work quite well for delivering a wad of SGML over great distances. Unfortunately, full-up SGML isn't particularly amenable to the Web and that's why we're here. XML is designed to bring the benefits of SGML to the Web in a manner that can be understood by mere mortals. This will allow more information to be delivered in meaningful ways than is possible with current web practice.
I don't view this as information loss, but rather information gain. We aren't down translating SGML, we're uptranslating the Web.
Sorry to take up your time with this but I've been a bit frustratedby this topic.