RE: Why are there no XSLT processors implemented in XS

> Roger -- Consider whether SQL processors are normally written in SQL, or
> unix shells in the languages they define.

This is not completely fair argument - I think it is not even theoretically
possible to write an SQL processor in SQL - I suppose that just parsing SQL
would require a language with greater expressive power. Also SQL expression
is not a set of relations, whereas XSLT input is XML.
On the contrary, XSLT surely is theoretically capable of making an XSLT
compiler. It might be an interesting, but hard exercise.

> Programs written to process XML should be implemented in XSLT.

"should" is very strong word, it almost seems as if you are implying that
people who are not writing XSLT compilers in XSLT are doing it wrong :).
The problem is that a large part of the compiler deals with internal
structures, lookup tables etc., which are produced after the first step of
processing - and those are easier to manipulate when stored as in-memory
objects than as XML data. 

Jakub.