Those are just a pull variant of a SAX parser.

People at BEA have done some work on that (They call it token stream):

Daniela Florescu, Chris Hillery, Donald Kossmann, Paul Lucas, Fabio 
Riccardi, Till Westmann, Michael J. Carey, Arvind Sundararajan, Geetika 
Agrawal: The BEA/XQRL Streaming XQuery Processor. VLDB 2003: 997-1008

http://www.informatik.uni-trier.de/~ley/db/conf/vldb/vldb2003.html#FlorescuHKLRWCSA03

The XTiSP system which was presented at PLAN-X in January seems to have
something similar as well:
# XTiSP presented by Keisuke Nakano (UTokyo) http://xtisp.psdlab.org/ 

XML pull token streams also used extensively inside the Galax's query 
engine.

There are probably other projects using those.
- Jerome

caml-list-admin@yquem.inria.fr wrote on 02/22/2005 12:07:18 PM:

> Hello world!
> 
> I have recently found a features in PXP named "pull parser", "event
> interface". I hope these things can help me with such a problems as xmpp
> streams parsing or huuuuge files parsing using Ocaml lazy streams (to 
avoid
> "Out of memory" errors). Can anybody suggest an url/other place to read
> more on these? I'm now reading the pxp source comments and version infos
> from it's site.
> 
> Thanks.
> -- 
> Yours truly, WBR, Paul Argentoff.
> Jabber:   paul@jabber.rtelekom.ru
> RIPE:   PA1291-RIPE
> 
> _______________________________________________
> Caml-list mailing list. Subscription management:
> http://yquem.inria.fr/cgi-bin/mailman/listinfo/caml-list
> Archives: http://caml.inria.fr
> Beginner's list: http://groups.yahoo.com/group/ocaml_beginners
> Bug reports: http://caml.inria.fr/bin/caml-bugs