Hi, On Thu, 2005-06-30 at 15:52 -0400, Liam R. E. Quin wrote: > On Wed, 2005-06-29 at 15:39 -0400, [EMAIL PROTECTED] wrote: > > > I cannot figure out how to use xPath without loading the entire XML into > > memory. > > This is an implementation-specific question, and for libxml2 the answer > is usually that you will need the whole document in memory. > > If this is a problem (e.g. very large documents) there are other > approaches, especially with XPath 2.0 -- XSLT 2.0 and XQuery which both > use XPath 2.0 can operate over indexed collections of documents, > although there are not yet many implementations of that feature, and > none I think using libxml2. > > The problem is that XPath expressions can easily be written that rely > on the entire document, e.g. count(//*) or section[position() = last()] > or using the ancestor axis to navigate around. A lot of research has > been done on optimising XPath, some of it in the database community, > especially in conjunction with XQuery (www.w3.org/XML/Query). > > Hope this helps although it might not be very encouraging! > > Liam
For people eager to dive into implementing streaming XPath for Libxml2: I found [1], a Java implementation for a subset of XPath, including predicates, to be quite informative for me. But just googling for "streaming XPath" will get you there anyway... [1] http://www.cs.umd.edu/projects/xsq/ Regards, Kasimier _______________________________________________ xml mailing list, project page http://xmlsoft.org/ xml@gnome.org http://mail.gnome.org/mailman/listinfo/xml
