Since ARABIC is a rich and highly inflected language [3], there are grammatical categories in ARABIC which do not exist in other foreign languages such as in ENGLISH [4]. For example, there is an ARABIC category called 'MAFOOL MOTLAK' which has no equivalent in ENGLISH. Moreover, there are syntactic categories in ARABIC which could themselves be a whole sentence or even a prepositional phrase . An example of such a category is the adverb . In addition, there are other differences in the order of the constituents within the sentence. For example, in ARABIC, adjectives follow the noun which they modify.

different from ENGLISH and hence, requires a different treatment.

LINGUISTICS

As the need increases to a model of ARABIC, ARABIC linguists try to re-organize the grammatic system in a way that may help the researchers in the field of computational linguistics. Linguists is traditionally concerned with formal, general, structural models of natural language. Linguists, therefore, have tended to build formal models which allow to capture, as much as possible, the regularities of language and make the most appropriate linguistic generalizations. Little or no attention has been paid to characterize the language itself, ignoring the mechanism that produce it or decipher it.

So, the researchers spent most of the time in re-building the models given by the linguists. Their aim was to make these models acceptable in computational field (synthesis, generation and translation).

We have Eight structures covering all the categories of noun phrases. FIVE of these structures are given here.

The notation used in describing these structures is brackets could be repeated more than once.

brackets could be repeated but it should exists once at least.

Representation is in

Chomsky's Normal Form and should be interpreted from right to left .

The structures given here consist mainly of NOUN (N) as the basic unit and its maximum allowable post-modifiers which could follow it These post-modifiers have a specific sequence which is the key to construct these structures and according to the number of these post-modifiers, the structures vary . The NP structures as well as some of the ARABIC categories they constitute, are given in Fig.(1) .

Example of a simple Arabic verbal sentence is given in Fig.(2) . In this example, the object of the sentence has all the post- modifiers given in the structure NP1 and It is clear that some of these modifiers have their own embedded structures shown in the embedded rectangles .

A. MODIFICATION

•MAFOOL ~'~MOTLAK' is a special modifier in Arabic which has a different forms depending on its post-modifiers. We have first [5] considered its structure as:

But later on, we have found out that both NC and ADJ can not exist simultaneously and only one of them should exist alone. So, we have split this structure to three structures

NP3, NP4 and NP.'S published here.

ACKNOWLEDGMENT

I would like to thank Dr. T. ANBER-' for her valuable discussion and support . Also, I would like to thank Dr. H. MAHGOUB(2' for his comments reviewing the paper and who, first, implemented most of the structures given here.

CONCLUSION

We have tried here to present the paper in a frame work showing that the study of computational modeling of ARABIC faces many problems. It is evident that the ARABIC possesses a certain symmetry as regards its structure, which leads itself easily to computation. This work is the basis of any further computational processing of ARABIC, leading to semantic analysis and eventually machine translation .