I didn’t see it at XML Europe 2004 (in fact, I didn’t go, though I wished I could have), but according to Eric van der Vlist, Alexander Peshkov of RenderX, Inc. gave a presentation on writing a RELAX NG schema for XSL-FO.
This leads me to a question: I wonder why the W3C did not provide a schema for XSL-FO 1.0 written in XML Schema? A search of the XSL-FO 1.1 working draft yielded no reference to XML Schema, so I am not sure such a schema is in the queue. I guess if someone needed it, he or she could use Trang to convert Mr. Peshkov’s RELAX NG schema to XML Schema.
Schemas can do more than just validate instances. They can concisely express to the human reader (in this case, a reader of the XSL-FO spec) just how to put a working XSL-FO document together. Ordinary English does not always do the trick (have you read the RSS specs?) I would hope that the W3C would provide a schema, in either RELAX NG or XML Schema, along with the XSL-FO spec in the future.
Do you think, like I do, that the XSL-FO spec begs for a supporing schema?