		Restricted Dependency Grammar
            -- An overview and program file list --

1. An overview of the software
   RDG (Restricted Dependency Grammar) is a Japanese dependency
grammar for syntactic analysis. In RDG, a constituent composed of a
sentence is called a phrase. RDG makes a dependency structure. It is
not a tree but a connected graph structure.


Japanese word order is said to be free, thus, dependency grammar, in
which only the relation between two arbitrary constituents is focused
on as a syntactic structure in a sentence, has been well studied. Many
natural language processing systems for Japanese have adopted the
dependency paradigm as an approach for syntactic analysis.

In general, two types of syntactic constraint are available for the
determination of dependency structures. One is the structural
constraint and the other is the linguistic constraint. The structural
constraint is how to make an arc which connects a pair of
constituents. The linguistic constraint is whether we can make an arc. 
The problem caused by these constraints is that useless solutions are
generated. These bring about a combinatorial explosion. Because
whether one constituent of a sentence modifies another constituent
concerns only localized information between the two constituents, such
as the selectional restriction between a verb and its complements.

We propose a dependency grammar formalism for Japanese called
Restricted Dependency Grammar (RDG). In RDG, a constituent of a
sentence is called a phrase. The structure of a sentence can be
produced by analyzing the binomial relation between phrases. One
characteristic of RDG is that the interpretation of whether one
constituent modifies the other or not depends on global information,
which makes use of the constraints among connections between a pair of
phrases in a sentence. So, we can suppress the generation of useless
solutions. Another characteristic is that every constituent of a
sentence except the last should modify at least one constituent on its
right. Thus, some linguistic phenomena, themes or ellipses can be
treated easily in our approach. In RDG formalism, every phrase and arc
has a rank value. The phrase rank is the classification of the phrase
based on the modifiability number. The arc rank is the classification
of the arc based on the connectivity between a pair of phrases. When
these values are satisfied, we can get the dependency relation between
the two phrases.

In the following sections, we will show the configuration of RDG and
a list program files.

2. Configuration of RDG and program file list
   RDG is currently implemented in SICStus Prolog Ver 0.7. In addition
to RDG, the parser program and input data are provided. The parser
employs a bottom-up parsing algorithm based on a parse table which
records the partial results produced during parsing. The parser
produces all possible dependency structures that satisfy RDG
constraints. The input data is the sample input data of RDG. The list
of program files is as follows.

(a) parser.pl
    Bottom-up parsing program

(b) rdg_gram_sem.pl
    RDG program

(c) dic.pl
    Program for dictionary

(d) 1002v03.dic
    Dictionary

(e) asahi.txt
    Sample for Japanese newspaper

(f) control.pl
    Program for input/output

(g) util.pl
    Utility program

3. How to install RDG
   The programs mentioned in section 2 are to be installed on a UNIX machine.

4. References

   F. Fukumoto, H. Sano, Y. Saitoh and J. Fukumoto
   A Framework for Dependency Grammar based on the word's
   modifiability level - Restricted Dependency Grammar -
   Trans. IPS Japan, Vol. 33, No. 10, to appear.
