libexpat1-dev - 2.5.0-1 main

This package contains the header file and development libraries of
expat, the C library for parsing XML. Expat is a stream oriented XML
parser. This means that you register handlers with the parser prior
to starting the parse. These handlers are called when the parser
discovers the associated structures in the document being parsed. A
start tag is an example of the kind of structures for which you may
register handlers.