In many ways XML seems to be the future of DocBook: more (free) tools are developped for XML, and it begins to be widely used in the Internet land in contrary of SGML that grows slowly. A possible reason of this situation is that the XSL stylesheet format is easier to understand and to learn than the DSSSL format; thus, stylesheet customization (at least for a beginner) is encouraged with XML.

At the writer level, there is no main differences since the defined elements are the same, even if SGML is more flexible (i.e. the ability to minimize or omit tags). The main point to decide whether using XML instead of SGML is if the DocBook's SGML branch is planned to be obsoleted one day or not.

Even if XML seems to be very promising, it is not mature enough, especially for printing documentation. Printed documentation tends to move one more toward DSSSL processors for output, and solid SGML tools chains exist that work as soon as it is installed. For instance the DocBook DTD / DocBook DSSSL / jade / [jadetex, pdfjadetex] chain is provided in the Red Hat distribution and works without big problems.

It seems that there are more XML tools, but the main problem is to make them work together! One step is to configure each of them, the other step is to manage specific configurations that make one work with another. For instance the XSL stylesheets provide some java archives, to add to the CLASSPATH to make the XSL processor used work!