optimization for very large, flat documents

I'm trying to process a very large (600 MB) flat XML document, a
bibliography where each of the 400,000 entries is completely independent
of the others.  According to the Saxon web site and mailing list, it'll
take approx. 5-10 times that (3 GB) to hold the document tree in memory,
which is impractical.  The Saxon mailing list also has some tips about
how to accomplish this, but my question is: Why doesn't XSLT provide a
way to specify that a matched node can be processed independently of its
predecessor and successor siblings?  Alternatively, couldn't an XSLT
processor infer that from the complete absence of XPath expressions that
refer to predecessor and successor siblings?

-- 
Kevin Rodgers