A Formal Description of Arabic Syntax in Definite Clause Grammar 
Hisham E1-SllisMny 
IBM Scientific Center, 56, Gameaat El-Doual EI-Arabeya St. 
Mohandesseen, Cairo, Egypt 
Abstract 
Arabic has some special syntax features 
which lead to complex syntax structures. 
We have developed a formal description 
of Arabic syntax in Definite Clause Gram- 
mar. This grarnrnar is characterized by its 
high descriptive power due to its dual for- 
mulation in terms of functions and in 
terms of grammatical categories. The de- 
veloped grammar has a high coverage of 
Arabic language and has context sensitive 
capabilities. It is suitable for the advanced 
applications of natural language process- 
ing. 
1o Introduction 
Arabic has some features which lead to 
comlpex syntax different from those of the 
European languages. Moreover, Arabic 
grammar exists cmly in a descriptive form 
and there is no comprehensive formal rep~ 
resentation for it so far. 
The few attempts to give a formal mod- 
e~ for Arabic sentences were based on 
transformational generative grammar - 
\[111, \[2\], \[3\] and others-but some linguists 
adopted more recent linguistic models 
such as Lexical Functional Grammar \[4\], 
dependency grammar \[5\] and functional 
grammar 16\]. 
Selecting a suitable grammar formalism 
for Arabic and the formulation of the 
grammar itself is the subject of a big de- 
bate in the Arab countries nowadays. Our 
descriptio:n of Arabic syntax in Definite 
Clause Grammar is different from the at- 
tempts undertaken so far. 
2. Deft,ire clat,se gram,,ar for Arabic 
syntax 
In this grammar, the arguments of non 
terminals are used to hold special features 
of Arabic words such as the definitely or 
indefinitely determined feature of norms 
which is essential to recognize many 
structures. Also, the ability of Definite 
Clause Grammar to provide a general 
treatment of context sensitivity through 
the proper use of arguments of non termi- 
nals makes it easy to account for agree- 
meats such as number, gender and person 
agreements. 
Another important characteristic of 
l)efinite Clause Grammar, which suits Ar- 
abic, is the possibility of imposing extra 
conditions on the constituents of a phrase 
which must be satisfied for a rule to be 
valid \[7\]. 
3. The develol,ed /ormal g,'ammar 
Due to the fact that there is IIO single 
basic word order for Arabic sentences, 
three basic sentence types were defined: 
a. Nominal sentence: a sentence that does 
not contain a verb or contains a verb 
which follows the subject. 
b. Verbal sentence: a sentence that con- 
tains a verb which precedes the sub- 
ject. 
c. Sentences with special structures such 
as vocative sentences. 
Sentences are further classified func- 
tionally and according to their modalities. 
Larger sentences are also described in 
this grammar by conjoining sentences or 
embedding simpler sentences. 
We have used the grammatical catego- 
ries together with the functional roles to 
define the syntactic structures. Grammati- 
cal categories alone were considered not 
sufficient to describe all the structures 
345 
since word categories in Arabic are global- 
ly classified into verbs, nominals and par- 
ticles only. Nouns, adjectives and adverbs 
for example are differentiated in tt'te sen- 
tence according to their functions. 
This dual formulation increases the de- 
scriptive power of the grammar. In order 
to use this dual formulation to define the 
syntactic structures, some non standard 
definitions of grammatical categories were 
used. 
A nominal sentence (ns) is defined for- 
mally as composed from a 'mobtadaa' 
phrase, mbp, and a predicate phrase, 
predp: 
ns(ns(MBP, PREDP)) -~ mbp (N,G,m, 
-., MBP), predp (N,G,n,PREDP). 
A mbp is defined as a noun phrase (np) 
that can have 'motaalkat' which are either 
a prepositional phrase (PP) or adverbial. 
A predp can be one of the following: 
• a noun phrase that can have 'motaal- 
kat' 
• a prepositional phrase or adverbial 
- a sentence which can be : 
- a verbal sentence 
- a nominal sentence (under certain 
conditions). 
Verbal sentences (vs) can be followed 
by either a subject phrase, sp, or a subject 
phrase and a complement phrase, cop: 
vs(vs(VP))-~ vp(T,V,S,I',VP). 
vs(vs(VP,SP,COP)) + vp(T,a,S,P,VP), 
sp(-,-,S,-,P,SP),cop(M,COP),{M=<T} 
cop(o,cop(\[ 1)) -~ I 1. 
For verbs in the passive voice the sp is 
replaced by 'naabfael' phrase (nsp), which 
can be either a np or pp. 
For non-terminal argument definitions 
the reader is referred to sections 3.1.1., 
3.1.2 and 3.1.3. Tlle values of the argu- 
ments indicated above are: a for active 
voice, n for indefinite determination, m 
for definite determination and - for accep- 
tance of any value. 
Verb phrases (vp) are defined as follows: 
vp --~ (cop), (particle), verb, (cop). 
whereas noun phrases (rip) are defined as 
follows: 
np -~ (particle), noutL (post- 
moditiers). 
Subject phrases are noun phrases 
whereas complement phrases modify the 
verbs and are one or more noun phrases 
(such as tile direct object) and/or preposi- 
tional phrases. 
The cop category is used to cater for the 
cases where the sp separates the verb 
from some of its modifiers, which is a 
characteristic of Arabic syntax. 
Sentences with special structures haw,, 
different structures which vary from one 
case to anotller. 
Sp and cop can be relative pllrases and 
in some cases the predp can precede the 
mbp. Categories with no equivalent in 
English are indicated between single 
quotes and categories inside the brackets 
are optional. 
3.1. Non Terminal mgu,tents 
Non-terminal arguments are used to 
hold features of Arabic words necessary 
for recognizing some structures and for 
allowing agreements between the differ- 
ent costituents of the sentence. Arguments 
are introduced in the lexical entries of 
words and are inherited by the phrase in 
which the words are constituents, h't this 
grammar, arguments are defined as fol- 
\]OWS: 
3.1.1. Arguments associated With verbs 
T transitivity, V voice, P person, S se- 
mantic feature. 
3.1.2. Arguments associated with nouns 
N number, G gender, D definite or in- 
definite determination, I:' person, S seman- 
tic feature. 
3.1.3. Arguments associated with pronouns 
N number, G gender, P person. 
M is an argument associated with senre 
non-terminals to test the possibility of 
modifying a verb witll objects. 
3.2. Use of semantic features to reduce 
ambiguity in Arabic senstences. 
Semantic features art, used with verbs 
346 
and nouns in order to test the subject verb 
semantic agreement. 
The use of the described semantic fea- 
tures in the developed grammar helps in 
the diifferentiation between the subject 
and the object in Arabic sentences, since it 
is not possible on purely grammatical ba- 
sis (except in some exceptional cases) to 
differentiate between them. 
3.3. Examples 
In this section, examples of the syntac- 
tic structures of a nominal sentence and a 
verbal sentence according to the devel- 
oped grammar are given. 
3.3.1. Example of a nominal sentence: 
Which means: 
the big dog is in the garden. 
In arabic, the definite article is a prefix, 
there is no copulative verb and direction 
of writing is from right to left. 
SIS /\ 
pF p 7 p 
pp np 
~ p ad} noun 
I I I I 
the garden in big the dog 
3.3.2. Example of a verbal sentence: 
Which means: 
the boy drinks the water in the house 
v,~ 
cop sp .- 
cop 
I 
PP /\ 
np np np p 
I r I 
the water the child the house in 
v 
L 
drinks 
4. Conclusiml 
This grammar has been implemented in 
a syntactic analyzer \[8\] developed in Pro- 
log on a 1'C/XT-286 and tested on a large 
number of Arabic sentences. 
It is hoped that the developed grammar 
will contribute to the efforts undertaken 
recently in the Arab countries towards the 
development of a comprehensive, agreed 
upon, formal grammar for Arabic syntax. 

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