This is dburg, a package that checks whether a tree grammar can be
used for optimal DAG parsing.  You can find a paper on the topic at
http://www.complang.tuwien.ac.at/papers/ertl99.ps.gz.  You can find
information about changes from previous versions in the file NEWS.

This software is copyrighted by Anton Ertl and is distributed under
the GPL (see the file COPYING).

There is no installation necessary. Just download it and unpack it with

tar xvfz dburg-x.x.tar.gz

It runs under Sicstus Prolog 3#6 (and probably other versions). The
source is plain Prolog, but it uses some of Sicstus' libraries.  I
plan to reimplement Dburg for a free language implementation.

The main program is dburg.pl. Six example grammars are included:

486.dburg	adapted from lcc's 486 grammar
examp.dburg	example grammar from the paper
inv.dburg	a grammar where the check fails
mips.dburg	adapted from lcc's MIPS grammar
proebsting.dburg a grammar where the check fails
rafts.dburg	adapted from RAFTS' MIPS grammar
sparc.dburg	adapted from lcc's SPARC grammar

You can run dburg on the examples with

sicstus -l file.dburg

The syntax for the grammars is a Prologified Burg syntax; see the
example files for details (the rewritten version will accept the
unmodified Burg syntax). The output contains some harmless asterisks,
and may contain some warnings and errors, together with information
about the conflicting states (if you read the paper, you may be able
to understand the additional info; better documentation is planned).

You can get the latest version at
http://www.complang.tuwien.ac.at/anton/dburg/
Report problems to anton@mips.complang.tuwien.ac.at.

- anton
-- 
M. Anton Ertl                    Some things have to be seen to be believed
anton@mips.complang.tuwien.ac.at Most things have to be believed to be seen
http://www.complang.tuwien.ac.at/anton/home.html
