LT XML is an integrated set of XML tools and a developers' tool-kit, including
a C-based API.

The LT XML tool-kit includes stand-alone tools for a wide range of processing
of well-formed XML documents, including searching and extracting,
down-translation (e.g. report generation, formatting), tokenising and sorting. 

Sequences of tool applications can be pipelined together to achieve complex
results. 

For special purposes beyond what the pre-constructed tools can achieve,
extending their functionality and/or creating new tools is easy using the
LT XML API. Minimal applications require less than one-half page of C code
to express. 

LT XML provides two views of an XML file; one as a flat stream of markup
elements and text; a second as a sequence of tree-structured XML elements.
The two views can be mixed, allowing great flexibility in the manipulation
of XML documents. It also includes a powerful, yet simple, querying language,
which allows the user to quickly and easily select those parts of an XML
document which are of interest. 

WWW: http://www.ltg.ed.ac.uk/software/xml/