A Formal Description of Arabic Syntax in Definite Clause Grammar

Arabic has some special syntax features which lead to complex syntax structures. We have developed a formal description of Arabic syntax in Definite Clause Grammar. This grarnrnar is characterized by its h igh descriptive power due to its dual formulat ion in terms of functions and in terms of grammatical categories. The developed g rammar has a high coverage of Arabic language and has context sensitive capabilities. It is suitable for the advanced applications of natural language processing. 1o Introduction Arabic has some features which lead to comlpex syntax different from those of the European languages. Moreover, Arabic g rammar exists cmly in a descriptive form and there is no comprehensive formal rep~ resentat ion for it so far. The few at tempts to give a formal mode~ for Arabic sentences were based on transformational generat ive g rammar [111, [2], [3] and o t h e r s b u t some linguists adopted more recent l ingu is t i c models such as Lexical Functional Grammar [4], dependency grammar [5] and functional g rammar 16]. Selecting a suitable g rammar formalism for Arabic and the formulat ion of the g rammar itself is the subject of a big debate in the Arab countries nowadays . Our descriptio:n of Arabic syntax in Definite Clause Grammar is different from the attempts under taken 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 de termined feature of norms which is essential to recognize many structures. Also, the ability of Definite Clause Grammar to provide a general treatment of context sensit ivity through the proper use of arguments of non terminals makes it easy to account for agreemeats such as number, gender and person agreements. Another important characteristic of l)efinite Clause Grammar, which suits Arabic, 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 contains a verb which precedes the subject. c. Sentences with special structures such as vocative sentences. Sentences are further classified functionally and according to their modalities. Larger sentences are also described in this g rammar by conjoining sentences or embedding simpler sentences. We have used the grammatical categories together with the functional roles to define the syntactic structures. Grammatical categories alone were considered not sufficient to describe all the structures