This section explains the XTAGDerivation output functor.
identifier: output.xTAGDerivation
open method: runs the tree viewer from
the XTAG lem parser package to show the derivation tree corresponding
to the solution. Currently used only for grammars generated by the
XTAG module of the XDK. Arbitrary many tree viewers can be run
simultaneously. For this function to work, the executables of the lem
parser (ftp://ftp.cis.upenn.edu/pub/xtag/lem/lem-0.14.0.tgz)
must be installed in the search path. The executable showtrees
is called.
