Re: XML Encoding of XPath: Examples

[Murata Makoto <mura034@attglobal.net>]

Eric van der Vlist wrote:
> Evan Lenz wrote:
> > I haven't worked out the implications of doing this, but it would feel more
> > natural and look more familiar to users of, say, TREX.
> 
> Yes, I hadn't expected it, but this is interesting to explore.
> 
> I find it amazing that this syntax that is a straight reformulation of
> XPath shows similarities between TREX (rules expressed in a XML syntax)
> and Schematron (rules expressed in XPath syntax) that were hidden before
> by the different syntax...

In the string case, regular expressions and finite automata (or regular 
grammars) look very different, but they are equally expressive.

In the tree case, we have a similar result.  The expression approach 
such as XPath (and thus Schematron) and the automaton approach such 
as RELAX and TREX are inherently equivalent.

More about this, see my PODS (Principles of Database Systems) 2001 
paper at:

	http://www.geocities.com/murata_makoto/podsMURATA.pdf

Cheers,

Makoto