XML tools and big documents

Henry S. Thompson ht at cogsci.ed.ac.uk
Thu Sep 3 18:08:17 BST 1998

Nigel Kerr <nigelk at umich.edu> writes:

> 	"what's the most immediate containing element of offset X in
> 	file Y?"
> 	"traverse up the logical structure from offset X until a DIV
> 	element with a HEAD is found, and return me the offsets of
> 	that HEAD"
> Exact expression language is, uh, gee.  These are the kinds of
> questions we could ask with "some XML query language", but if i have a
> gigabyte or so of variously-structured English text marked up this
> way, i really don't want to have to parse the document entity just to
> answer these kinds of simple questions.  This is a weak specification
> of what I'm trying to do, i realize.  (this all largely because i am

Our LT XML tool set and API were designed for precisely this sort of
application (we regularly work with >1GB language SGML-encoded corpora
such as the BNC).  We get good performance because

1) Our parser is written in C, our search and retrieval tools use it
   directly via a stream-based API, only custom UI tends to get
   written in a scripting language which looks at whole trees;

2) We only produce tree fragments when we get to the interesting bits:
   our query processor is optimised to avoid building large amounts of
   tree unnecessarily;

3) For REALLY big datasets, we do produce and use offset-based

For more information, see http://www.ltg.ed.ac.uk/software/xml/.

  Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh
     2 Buccleuch Place, Edinburgh EH8 9LW, SCOTLAND -- (44) 131 650-4440
	    Fax: (44) 131 650-4587, e-mail: ht at cogsci.ed.ac.uk
		     URL: http://www.ltg.ed.ac.uk/~ht/

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