first let me introduce myself quickly - my name is Thomas Geiger, currently a CS student at the Vorarlberg University of Applied Sciences (
http://www.fhv.at).
By begin of February I'll start working on my diploma thesis which aims to integrate GNU Octave into a grid environment (based on Globus Toolkit -
http://www.globus.org/toolkit/) and - as you could imagine - this road map might also include XML support (read/write) for Octave.
Just my two cents on XML - after having taken a look at the XML threads of this list, my favorite approach is 6 (a custom written parser,
http://wiki.octave.org/wiki.pl?XML-tools-for-Octave). The proposed solution would make use of a well performing parser like expat (benchmarks neet to be done on this choice), and follow 4 (geodise toolbox) from a functionality point of view.
For an initial version I'd suggest to stick on a Octave only format (validated by XSD), the import of other formats/standards (also MatLab?) could be handled by usage of XSLT transformations/further hacks later on (hopefully).
Important for me to know - is already someone working on this, otherwise I'd like to - of course there needs to be some more detailed negotiation regarding the features.