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					                        ‫ٔذٛ ذٌٛ١ذ آٌٟ ٌٍّصطٍذاخ اٌؼشت١ح‬
‫الدكتور / سعد بن خالد الجبري (*)‬



‫ً‬                                                            ‫ّ‬
                                                             ‫ظ‬          ‫بن‬
‫ذّراص اٌٍغح اٌؼش ٠ح َ ث١الذٙا اٌ اِ١ح تكٚج االػذماق اٌصشفٟ، ٚفٟ ٘زٖ اٌٛسلح ٔمذَ ذص ٚسا‬
                                 ‫ؽد‬         ‫ٞ‬                                      ‫ًٞ‬
   ‫حعثٗ جد دا فٟ ٔظشذٗ إٌٝ اٌذالٌح اٌصشف١ح اٌّثٓ ج ػٍٝ اال لاق. ٚ٠غذّذ ٘زا اٌرصٛس ػٍٝ‬         ‫ْ‬
     ‫ًٌ‬                                                        ‫تٟ‬                       ‫ٞ‬
‫ِغرْٛٞ ِٓ اٌذالٌح ٠ُ وٓ اٌرّ١١ض ّٔٙا ػٕذ ذذٍ١ً دالٌح االؽرماق، أٌّٚٙا اٌذالٌح اٌُ صا دثح ج رس‬
   ‫ٚاٌثأٟ اٌذالٌح اٌّصادثح ٌٍص١ؾ اٌصشف١ح . إْ ذفاػً ٘زٖ اٌّغدٚ٠اخ اٌذالٌ١ح ٠ٌٛذ ِفا٘١ُ ِرىاٍِح‬
                                                                         ‫ٟ٘ج‬
                                                         ‫٠ُ وٓ اعر١ؼاتٙا ػٍٝ ئ ِؾرماخ ػشت١ح .‬
   ‫ٌٚؼً اٌٙذف ِٓ ٘زٖ إٌظ سج إٌٝ اٌذالٌح اٌصشفٟ ج ٠ىّٓ فٟ اٌرؼشف ػٍٝ عثً اٌشتط ت١ٓ‬
                                                        ‫خ‬
 ‫ا َ فا٘١ُ اٌذالٌ١ح ٚاٌىٍّاخ اٌؼشت١ح ف١ّا ػٛسف ػٍ١ٗ فٟ ػٍُ ذٌٛ١ذ اٌٍغح تاعُ االخر١اس اٌصشف‬   ‫ي‬
   ‫اي‬      ‫خ‬                                ‫ٞ‬
                                            ‫ب‬
 ‫ٌٍّفشداخ ‪ٚ .Lexical choice‬ذجذس اإلؽاسج ٕ٘ا إٌٝ اٌط عج اٌخاصح ٌٍغح اٌؼشت١ح وٍغح اػ لال١ح ٚ ذٟ‬
                                                                    ‫ذً ً‬           ‫ئ‬
‫ذرطٍة ٚعا ي أخشٜ ؽ٠ش ن ٚفشخ ٌٍغاخ واإلٔجٍ١ض٠ح ِثال. ٚ٠ؼذ االخر١اس اٌصشفٟ ٌٍّفشداخ ِٓ‬
                                                                      ‫خ‬
  ‫األِٛس اٌالصِح ألٔظّح اي سجّح ا٢ٌ١ح ٚٔظُ ذٌٛ١ذ اٌٍغح ، ٚ٠رطٍة ذٕف١زٖ خٚفش اٌٛعائً اٌالصِح‬
     ‫اٌد‬                            ‫ذظ ٖ‬          ‫ٞ‬            ‫تٟ‬
 ‫ٚت١ح) ٌٍشتط ْ ِغٔٝ ِغ ْ ٚوٍّح ذٛعب فٟ ٌغح اٌٙذف، ٚػٍ١ٗ فإْ ٌٚ١ذ‬            ‫(ٌغٛ٠ح وأد أَ داط‬
     ‫ي‬
‫ٞ ٌٍّـصطٍذاخ اٌؼشت١ح ألشب ِا ٠هْٚ فٟ طث١ؼرٗ إٌٝ االخر١اس اٌصشفٟ ٌٍّفشداخ ٔظشا ٚدذج‬         ‫ا٢ي‬
                                                                    ‫اٌٙذف ٚاٌّفَٗٚ اٌٍغٛٞ ٚاٌرك‬
                                                                  ‫ٟٔ.‬
                                                                                ‫اي‬
   ‫ٚفٟ ٘زٖ ٚسلح ذُ اٌرؼشض ٚ تؼوً ِٛ جص إٌٝ ايِٛاصفاخ اٌذالٌ١ح ٌٍّؾرماخ اٌؼشت١ح ِٚٓ‬
‫ظّٕٙا اٌّصطٍذاخ إظافح إٌٝ اٌرمٕ١اخ اٌّشذثطح ٌٙزا اٌُ ج اي، ٚذُ الرشاح ذص ٚس جد٠ذ ٠طا ي‬
              ‫ٚري‬
 ‫ٞ ٟٔ ػٍٝ دالٌح االؽرماق، ٚاٌطشق اٌّّىٕح ٌرٕف١زٖ آٌ١ا ن تثٕاء ؽثىح‬ ‫االخر١اس اٌصشفٟ اٌؼشب اٌّة‬
                                           ‫ف‬                    ‫ا٢ي‬             ‫ؤ‬
  ‫دالٌ١ح ٚاسث١ح خِٓ اٌرصٕ١ف ٞ ٌٍّذخالخ ػٕذ ذٓ٠ز٘ا تٛاعطح أٔظّح ذّث١ً اٌّؼاسف ٚخاصح‬      ‫خ‬
                                                                ‫خ‬        ‫خ‬
 ‫ػائٍح ‪ KL-ONE‬وّا ذُ ٚظ١خ ٚج٘اخ اٌرصٛس اٌز ٞ ذمذِٗ ٘زٖ اٌٛسلح تأِثٍح ٌّذ خالخ دالٌ١ح‬
  ‫اٌٙذف ِٕٙا ذٌٛ١ذ تؼط اٌّصطٍذاخ اٌؼشت١ح، ٚ جسٜ اٌرٕف١ز ػٍٝ ٌِٛذ آٌٟ ٠غرخذَ لاػذج ِؼشف١ح‬
                                                   ‫ِثٕ١ح ػٍٝ دالٌح االؽرماق فٟ اٌصشف اٌؼشتٟ.‬




                                                                                             ‫*‬
          TOWARDS THE AUTOMATIC GENERATION OF
                                ARABIC TERMINOLOGY
                                                                                Saad K Al-jabri'1




         Abstract: in this paper we show that semantic specifications can be described for Arabic
derivation. Moreover, semantic interactions that hold between features associated with moulds and
meaning representations expressed by roots can be exploited in the process of Arabic lexicalisation.
Such a process, with no doubt, will benefit the automatic generation of Arabic terminology. We
discuss current approaches to lexicalisation and show that Arabic requires a new framework that is
consistent with its nature as a derived language. Our analysis covers linguistic issues as well as
computational ones on the linguistic side, we study Arabic derivation from a semantic point of
view. On the computational side, we show that semantic aspects of Arabic derivation can be
expressed as a semantic taxonomy. Taxonomic organisations are implemented by KR systems that
support automatic classification. Such systems are useful when implementing Arabic derivation in
which they allow for the KB to be free from redundant information and derivation occurs at
classification time. Finally, we demonstrate our approach to Arabic lexicalisation by generating
some terminological terms using a generator that is based on semantic principles discussed in this
paper.




1
    Data Processing Center-KFSC, Kingdom of Saudi Arabia,
I Introduction                                       languages such as Arabic runs against the

      In this paper we introduce a new               spirit of the language and leads to a great

framework for systems that perform Arabic            redundancy in the knowledge-base.

lexical   choice     focusing       on     Arabic          In Arabic, derivation is a major word-
terminology.     Lexical choice also called          formation process that relates words in the
Lexicalisation, is the process of mapping            language. Generally speaking, Arabic words
semantic representations onto lexical items          are built around consonantal roots which can
(words in the language).          While native       be linked to core meaning representations.
speakers of a language seem to face no               The consonantal roots are modified by
difficulties in finding the words to express         derivational     processes    using    derivational
themselves, computer-based systems need to           affixes.   Derivational affixes, in turn are
address the complex character of the task.           associated with general semantic features.
Lexical choice is at the heart of generation         When a derivational process occurs the
and having good lexicalisation systems is            physical shape of the root will be altered and
important for systems that will convey ideas         so as its meaning representation.              The
in   natural    languages      (e.g.,     Machine    interactions between roots and derivational
Translation (MT) and Natural Language                affixes allow us to study derivation not only
Generation (NLG) systems). The present-day           from a structural point of view but also from a
frameworks for lexicalisation have all been          semantic       one.       Semantic     interactions
originally developed having English as a             motivated by derivation can be exploited in
target language in mind.         English has a       the process of Arabic lexicalisation.         This
morphology which is not as productive in its         implies utilising such interactions in building
overall    derivation     as      some       other   semantic networks that support the mapping
morphological systems such as those found in         between meaning representation and Arabic
Semitic languages.      This may explain the         derived words including terminology, This
absence    of      derivationally        motivated   paper is organised as follows:
approaches to the problem of lexicalisation
                                                        Section 2 introduces Natural Language
even for some very productive processes
                                                     Generation and its components focusing on
expressed by English.       Applying existing
                                                     lexicalisation        techniques      and   their
approaches, which treat words as isolated
items, to the lexicalisation of highly derived
applicability       to    Arabic   as   a   derived     to express them as sentences in the target
language,                                               natural language. The consensus view as to
                                                        what processes generation looks as follows
     Section 3 provides an overview of
                                                        (McKeown88,Reiter94,Nicolov96]:
Arabic     derivation       and    introduces   our
approach to derivation as a semantic                          Content Determination: The meaning
process.     This section describes also the            to be conveyed is determined taking into
derivation of Arabic terminology and their              account the communicative goals.                  The,
semantic specifications,                                semantic      structure       produced   might     be
     Section 4 describes the computational             annotated by rhetorical structure theory
model which includes building a semantic                relations.
taxonomy and describing possible ways for                     Sentence          Planning:    Splitting     the
implementing the taxonomy.                              relatively big semantic structure at the output
     Section 5 concludes the paper by                  of the previous stage into units that can be
summarising the ideas presented so far,                 expressed as sentences (or clauses).
2 Lexical Choice in NLG Systems                               Lexical choice: Choosing content words

       Natural language generation (NLG) is             and (abstract) grammatical relations.

the process of realizing communicative                        Surface realisation: Choosing syntactic
intentions as text (or speech). Generation is           structures and introducing closed class words
often split into strategic generation (what to          (auxiliaries, prepositions).
say) and tactical generation (how to say it)                  Morphology: Performing declination of
[Thompson, 77]. In choosing what to say a               words.
generation system will need to consider how
                                                              Synthesising              speech/Formatting:
the      original        communicative      intention   Producing speech from the syntactic tree
determines the meaning to be conveyed, and              Alternatively,     systems      producing   written
then how this meaning can be organized as a             output might perform some kind of formatting
sequence of sentence-sized meaning units and            at this stage.
how these can be structured. In choosing how                  In this paper we address lexical choice
to say it a generation system will take the             in   Arabic      that    is   well-known    for    its
sentence-sized meaning units and will attempt           derivational productivity. We first look more
closely at the standard notion and techniques       current lexical choosers are still far from the
of lexical choice and then discuss how dealing      performance of humans. Lexical choice is at
with a productive derivation such as Arabic         the heart of generation and having good
derivation requires a different model of            lexicalisation     systems   is     important   for
lexicalisation.                                     systems that will convey ideas in natural
                                                    languages (e.g., Machine Translation MT
2.1 Lexicalisation Techniques
     Lexical choice (lexicalisation) is a           systems and NLG systems).
process of mapping meaning representations
onto lexical items (words in the language). A             Early approaches in NLG assumed very

generation system will need to identify (all)       simple connections between words and

possible words and choose among them the            concepts (one-to-one mappings, which have

best candidate in a particular situation.           sometimes been referred to as capital letter
Performing lexical choice is non-trivial            semantics). A more sophisticated approach
because the meaning representations are not         was exemplified by the development of
directly linked to words (i.e., a large number      discrimination nets (also called (d-nets)
of words may apply in any situation) and            [Goldman75], which map a concept to one of
choosing the right word requires knowledge          the near-synonymous words that represent
not only about the semantics but also about         possible realisations of that concept. This is
syntax and pragmatics.       In general, lexical    achieved by providing for each semantic
choice communicates with other processes            primitive a decision tree with possible words
and decisions in an interactive way and the         attached to its leaves.      Accordingly, every
consequences of choosing a word might be            word sense has associated with it a set of
far-reaching and not immediately apparent           defining         characteristics.           These
[Zock9O,Nogier92).                                  characteristics are predicates which must be

      Native speakers of a language seem to         satisfied    by       the    input      conceptual

face no difficulties in finding the words to        representation in order for the input to be

express    themselves,     yet     computer-based   realised using that word. For example, the, d-

systems    need   to     address    the   complex   net for the primitive concept INGEST can be

character of the task. At present, researchers      related to different verbs such as eat, drink

have no good insights or indications as to how      and inhale. When trying to map a concept to

humans perform lexical choice so easily and         one of these verbs, the d-net is traversed to
determine the realisation of the concept based       called frames which represent classes or
on a sequence of queries regarding the               objects. Each frame has a number of data
instance being ingested.        Accordingly, the     elements called slots.      Each slot contains
concept will be realised as eat if the object is     information about attributes such as values
solid or drink if the object is liquid and so on.    and restrictions on possible fillers [Woods92].
However, the use of highly abstract semantic         The DIOGENES system provides a frame for
primitives in d-nets has made them less              every lexical item in the Knowledge-Base
popular in recent NLG systems. Nevertheless,         (KB) in which each frame specifies a concept
d-nets have proven to be highly influential for      along with some restrictions on particular
subsequent work in generation [Stede95].             roles of the concepts [Nirenburg88).         For
                                                     example, the frame for the word boy has the

      The next generation of lexical choice          following representation:
systems organised lexical knowledge as
inheritance hierarchies in which subordinate              Boy:

concepts inherit the properties of their super-           CONCEPT-SLOT:                    person

ordinates    (e.g.,   the    LOQUI      generator         SEX:                             male

[Horacek87]). As a result, the primitives are             AGE                              12-15

not as abstract as those of d-nets and
inheritance mechanisms are exploited to
                                                          Other restrictions on concepts can be
reduce the redundancy in the representation.
                                                     described in a similar way. Typically a frame
However, the semantic primitives described
                                                     system will include an is-a link (X is-a Y) in
for concepts remain in general sin-War to
                                                     terms of pointers to more general frames or
those of d-nets. The need to constrain
                                                     frames from which additional slots with
concepts by means of restrictions (motivated
                                                     default values and other information may be
by the participant roles of more complex
                                                     inherited. However, in frame-based systems,
concepts     describing     different   types   of
                                                     there is no formal criterion for when such
situations) encouraged some researchers to
                                                     links should be added to a frame. It is simply
explore the possibility of using frames in
                                                     up to the designer to decide where a concept
representing concepts expressed by lexical
                                                     should be inserted into the hierarchy. When
items.      Typically, a frame-based system
                                                     choosing a word, all frames and their slots
consists of a collection of data structures
    need to be examined to filter out unrelated                            This concept can be subsumed by a
    frames. While more structure is brought to                       concept expressed by the word man which
    the concept representation by this approach                      has the following definition:
    the   computational           cost        resulting     from
                                                                           PERSON with attributes sex: male, age-
    examining        all      frames          is     too    high.
                                                                     status: adult.
    Furthermore, unlike d-nets, despite the use of
    fine-grained semantic distinctions for each                            The second concept is more general
    concept there is no guarantee that the system                    since it contains less information, A typical
    will always come up with an answer,                              scenario for language generation present-day
                                                                     is a semantic representation based on some
          As    an         alternative        to     the    above
                                                                     taxonomic knowledge-base which has to be
    mentioned     approaches             to        lexicalisation,
                                                                     verbalised [Stede95]. In contrast to frame-
    taxonomic     knowledge-bases                   have     been
                                                                     based systems, taxonomic knowledge-bases
    introduced to bridge the gap between meaning
                                                                     define the is-a relationships by an external
    representations         and    linguistic          resources,
                                                                     semantic criterion independent from the data
    Taxonomic        knowledge           bases        for   NLG
                                                                     structure [Woods9l].        Some systems utilise
    organise world entitics in semantic networks
                                                                     such representations to implement lexical
    with different levels of abstraction. Concepts
                                                                     choice by means of automatic classification
    appear as classes in structured inheritance
                                                                     (IDAS [Reiter92).2
    hierarchies organised according to their
    generality (subsumption relationships) where                     2.2 Morphological Derivation and Current
                                                                     Approaches
    the more specific classes inherit properties
                                                                           Most       of   the   NLG     research     has
    from the more general ones. Roles can also
                                                                     concentrated on Indo-European languages and
    be defined to describe relationships between
                                                                     within this almost entirely on English. The
    different concepts. As a consequence, there is
                                                                     present-day frameworks for generation--the
    more structure that can be exploited in
                                                                     systemic approach, the functional unification
    lexicalisation [Bateman9l]. For example, the
                                                                     approach and the classification approach have
    concept expressed by the word bachelor can
                                                                     all been originally developed having English
    be defined in a taxonomic K.B as follows:
                                                                     as a target language in mind. Lexicalisation
          PERSON             with attributes sex: male,              models, as a consequence, have been geared
    age-status: adult, marital-status: unmarried,                    mainly towards English. Such models can be


2
 Automatic classification refers to the ability of a system to automatically classify with respect to an existing taxonomy
[Woods 921.
abstractly summarised as mapping semantic,                        applied to highly derived languages such as
configurations onto lexical items (using some                     Arabic. For example, in the derived lexicon
variants of the, techniques described above),                     of Arabic (i.e., a lexicon that contains all
the chosen lexical items in the course of                         words derived from consonantal roots in
surface   realisation       are     augmented         with        Arabic); there are clear derivational links
morphological features; after the syntax tree is                  between      words     and   ignoring     them    in
generated a morphological postprocessor                           generation     (and     more    importantly       in
inflects the words.               This means that
                                                                  lexicalisation) runs against the spirit of the
morphological         derivation     has      not     been        language and leads to a great redundancy in
considered in the existing approaches to                          the KB.
lexicalisation.        For example, present-day
                                                                  3 Arabic Derivation
generators      (e.g.,    the      Penman           project
                                                                        Arabic derivation forms stems (verbs
[Bateman95]) do not consider the lexical
                                                                  and nouns) by means of consonantal roots and
relatedness       between         verbs      and      their
                                                                  derivational affixes, A single root can give
derivatives such as write and writer despite
                                                                  rise to different derivationally related stems,
the productive nature of this derivation in the
                                                                  As a consequence, the majority of Arabic
English      language.      In      general        Current
                                                                  words (verbs and nouns) are built up from a
approaches to lexicalisation tend to treat
                                                                  relatively small number of roots.                For
concepts as related entities; words, on the
                                                                  example, an Arabic root and some of its
other hand, are viewed as isolated items that
                                                                  derivatives are listed in Table 3. 1:
just happen to be attached to concepts. These
approaches have limitations when they are

Arabic        Transliteration Derivational                    Arabic root English lexeme           English root
Lexeme                        mould
              kataba          fa‟ala                              ktb       to write               write
              katib                 fa‟il                         ktb       a writer               write
              kataba                fa‟ala                        ktb       to correspond          corespond
              maktab                maf‟al                        ktb       an office              office
              maktaba               maf‟alat                      ktb       a libirary             library



                             Table 3.1 : Some lexemes derived from (                      ktb)
      The     sub-regularity      associated     with   a   possible     triliteral   consonantal     root
Arabic derivation led traditional grammarians,          modification.     These moulds are generally
to develop a morphonological theory that                adopted following the work of Arabic
describes Arabic derivation (morphonology is            Grammarians.         The convention in Western
constituted by the interaction of morphology            studies is to refer to them by their Roman
and phonology [Dressler85]). In this theory,            numbers (I - XV) [Wright75]. The derivation
medieval grammarians used notations, which              of quadrilateral verbs and nouns is also
we will call moulds, to mediate between                 described in traditional work.       Moulds for
words and their morphological shapes3 A                 nouns are numerous and less regular than verb
mould is a template that reflects the                   moulds. Unlike verb moulds, noun moulds
occurrence of consonants and vowels in a                have no conventional numbering system.
particular word structure.          In the mould
                                                              Arabic     derivation    associates     verb
system, the consonantal root is represented by
                                                        moulds with semantic features such as
three or four selected letters (         f, l) or (
                                                        causality, intensity, reciprocity, reflexivity and
      f’ll) or depending on whether the root is         human characteristics. For example, mould II

trilateral   or   quadriliteral    (trilateral   root   is always associated with intensity while

consists of three Arabic consonants while a             mould IV is associated with causality. Noun

quadrilateral root consists of four Arabic              moulds are also associated with features to

consonants). Vowels and other derivational              describe objects such as action agents, action

affixes are copied to the mould form                    patients,   tools,    instruments,   places   and

unchanged, For example, the third column in             machines.

Table 3.1 associates all lexemes in the Table
                                                        3.1 The Derivation of Arabic Terminology
with their derivational moulds.
                                                              In this work, we will refer to derivation
      Moulds were introduced, traditionally,
                                                        as the morphological term that describes the
to describe derivation and to account for the
                                                        process of word-formation by means of the
productivity of Arabic word-formation. They
                                                        interactions between roots and derivational
are widely regarded as a classification system
                                                        affixes     (including    infixes)   in     Arabic
for Arabic derived Words. Arabic trilateral
                                                        morphology. In particular, it is equivalent to
root-based verbs are classified into fifteen
                                                        what Arabic grammarians call
moulds. Each mould reflects one instance of
lstiqaq). Derivation, in this context, has been             “Pen case” 76               All these terms and
a major formation process that incorporates
                                                            many more are derived from consonantal
words in the Arabic language.         The set of
                                                            roots according to well defined derivational
Arabic terminology includes many derived
                                                            rules. The nominal derivation plays an
words. Derivation can also be applied to form
                                                            essential role in terminology derivation.
new ones, For example, the following are
                                                            Arabic morphology provides a set of moulds
some derived terms that have been "recently"
                                                            that support the derivation of terminological
introduced in connection with office supplics
                                                            terms under specified Subjects such as
:         Mufakkirat “agenda”,           dabbast
                                                            machine place and time. Table 3.2 lists some
“stapler”,        Taqwym “calendar”,                        noun moulds in connection with their
                                                            semantic features.
kharramat “Perforator and              maqlamat



    Mould          Transliteration        Feature            Example     Transliteration           English
                       Fa‟il            Action-agent                         Katib                An author
                      Maf‟wl           Action - patient                      Maktwb              A document
                       Fa‟‟al         intensified-agent                      „ Ilam                a scholar
                       Maf‟il        an event time/placee                    Maw‟id             An appointment
                       Maf‟al           An vent place                        Maktab                an office
                       Mif‟al            Instrumenrt                         Miftah                  a key
                       Fa‟wl                Tool                             Satwr                a chopper
                      Fa‟‟alt             Machine                            hassabt              a calculator



                      Table 3.2: Noun moulds and semantic features

3.2 Semantic Interactions in Arabic                         States, processes and objects. A consonantal
Derivation
                                                            root accounts for a semantic representation
         Derived words in Arabic are formed by              that appears in a set of derivationally related
applying derivational affixes to consonantal                words.   Roots       in   non   -   concatenative
roots.     Such   words   are   realisations   of           morphology are discontinuous morphemes
independent concepts that describe actions,                 (i.e, they can be interrupted by other
morphemes). It is almost always difficult (if      A semantic feature is a unit of meaning that
not impossible) to describe precisely the          is associated with a mould and that can be
meaning of a consonantal root. We associate        used to distinguish one concept realised by a
consonantal roots with core meanings. A core       word sharing the same consonantal root.
meaning is defined as follows:
                                                         For example, the mould appearing in the
                                                   first row of Table 3,l describes a general
A core meaning is a semantic representation
that appears in a set of derivationally            action as a semantic feature.          Another

related words.                                     semantic feature is associated with the mould
                                                   in the third row of the same table which
      For   example,     the     Arabic   words
                                                   describes a more specific action: a reciprocal
appearing in Table 3.1 share one consonantal
                                                   action.     Reciprocation, in this case, is a
root, that is          k t b      This root is
                                                   semantic feature associated with the mould
associated with a core meaning that has            (         Fa’ala). Semantic features associated
something to do with the activity of writing.
                                                   with moulds can be viewed as semantic
      It is also necessary to consider the         generalisations in the Arabic word-formation
semantics of derivational affixes appearing in     system, Such generalisations usually help
moulds, These affixes represent morphemes          native speakers of Arabic to make educated
that have been added to the mould in a layered     guesses about new words they have never
process. The integration of various layers in      heard before. This would mean that mould
the mould from result in an integration of         semantic features could help in analysing the
different morphemes to describe a set of           Arabic word-formation system not only for
semantic features. A semantic         feature is   the existing words but also for potential new
associated with its mould as a whole unit and      words in the language. In fact, it provides a
cannot necessarily be described by means of        high level representation of semantics that
individual morphemes involved in the layered       integrates words (including new ones) into the
process.    Accordingly, a semantic feature        language system by linking their semantic
accounts for another level of semantic             features.
representation and can be defined as follows:
                                                   3.2.1 Concept Formation
         The above discussion indicates that                              The semantic specifications of derived
forming a concept which is realised by a                           concepts vary from one class of concepts to
derived word requires two major semantic                           another.     The semantic variation between
components, a core meaning and mould                               classes can be identified by the type of
semantic features, Semantically, roots are                         semantic features associated with moulds and
representatives of core meanings in the                            the type of core meanings the modify. We
language.        A single root describes a core                    classify derived concepts into three main
meaning that does not account for the full                         classes, namely, action, state and derived
meaning of a particular concept. in order to do                    object. Semantic features that modify core
this, it needs additional semantic features                        meanings under action include causation,
associated with an applicable mould. Moulds,                       intensification, reciprocation and reflexivity.
on the other hand, are abstractions, which can                     These features are associated with moulds IV,
say something about the common concept of                          II, III and VII respectively4. Semantic features
the meanings of the words that they represent                      under state modify state core meaning to
but cannot tell the whole story. Putting                           generate stative concept such as feeling and
together the two semantic aspects (i.e., core                      emotion (e.g           fariha). Concepts that
meanings and mould semantic features)
                                                                   describe derived object utilise features that are
allows the formation of concepts that describe
                                                                   associated with noun moulds and are linked to
particular situations through the construction
                                                                   both action and state concepts.       To define
of derivatives.         For example, the concepts
                                                                   domains for each class, core meanings are
realised by the Arabic words in Table 3.1 can
                                                                   also classified into action and state core
be represented by means of the semantic
                                                                   meanings. Such classification is motivated by
interactions that hold between the core
                                                                   the appearance of a root in a verb represented
meaning associated with                    k, t, b), on
                                                                   by mould I, whether that verb describes an
the one hand and the semantic features                             action concept or a stative one. Accordingly,
associated with their derivational moulds on                       action concepts apply only to action core
the other.         Thus we are going to view                       meanings while stative concepts apply only to
derivation as a parallel process of word and                       state core meanings.      Derived objects are
concept formation.                                                 linked to both of them.


4
    Not that a feature such as reflexivity could be associated with more than mould.
      When forming a concept from semantic             be used to direct semantic descriptions to the
descriptions, features that can be associated          appropriate classes.
with moulds are linked to their moulds and
representation that can be associated with core        3.3 Productive Concepts
meanings     are   linked   to     corresponding
                                                             Since our concerns are going to be with
consonantal roots. This results in providing a
                                                       the derivation of Arabic terminology, we
mould and a root which are enough to form a
                                                       introduce here productive concepts which can
word by mapping the chosen root into the
                                                       be defined as follows :
selected mould template.         For example, a
semantic      description        that       includes         A productive concept is a concept that
intensification as a feature and computing as          results from the interactions that hold
an activity should be linked to mould II (             between core meanings and the semantic
                                                       features associated with noun moulds.
fa’’ala ) and the root           hsb        The root

then can be mapped into mould II template to                 According to the above definition

form the Arabic word (                  hassaba) "to   semantic interactions that result in forming
                                                       terminological concepts fall under productive
calculate". Further more. The concept that
                                                       concepts as nominal derivation.
includes in its description the same concept
above and, in addition, a pointer to indicate                Traditionally, Arabic nouns can be
that machine derivation is at focus rather             grouped into two classes as regards to their
than the action concept, such a description            origin: primitive and derivative.            The
will result in mapping the derivation into             primitive nouns are all substantive (e.g.,
mould (        fa’’alat) while keeping the root
                                                       ragul “a man”). The derivative nouns may be
as it was before. This leads to the formation of       substantive such as          miftah "a key") or
the Arabic word (                   hassabat) “a
                                                       what corresponds, in English to adjectives
calculator" as a derived object.                       such as (          maryd ",sick) [wrig‫ا‬it51].

      However,     since    semantic        features   Moulds for nouns are numerous and less
associated with moulds are too abstract,               regular than verb moulds.         Unlike verb
participant roles such as actor and actee may          moulds, noun moulds have no conventional
numbering system. The majority of derived                       Place, as defined above, is associated
nouns are linked to verb moulds and their                  with the mould            maf‟al) and is linked to
derivation is described traditionally by means
                                                           default concepts that are represented by the
of modified verb moulds.
                                                           mould I ---         fa‟ala). For example, from
      In this work, productive concepts are                      kataba) " to write,             sakana) " to
regarded as being formed by applying features
                                                           inhabit' and       sariba) “to drink “ we could
associated     with   noun     moulds        to     core
meanings which are realised by derivative                  derive            maktab) "an office”,
nouns as productive stems.              The most
                                                           maskan) "a house" and (                Masrab) “a
common        productive    features    in        Arabic
                                                           place for drinking" respectively.          Arabic
derivation     include     action-agent,      action-
                                                           derivation provides other moulds associated
patient, place, instrument and machine [Al-
                                                           with the location feature. However, they are
Rajihi84].
                                                           rarely used and we do not consider them here.
      In the following we describe the
                                                           3.3.2 Instrument
semantic interaction of the most common
                                                                Instrument as a feature is defined as
productive features that have been used
                                                           follows:
frequently in deriving terminology, namely,
place, instrument and machine.                                  Instrument is a productive feature that
                                                           applies to causative actions to describe
3.3.1 Place
                                                           manual tools that can be used to perform
      Arabic derivational processes provide
                                                           actions without need for external power.
the means for deriving concepts that describe
other aspects of actions such as physical                       Instruments are derived from causative
location.     Place as a semantic feature, is              actions. However, it is obvious that not all
defined as follows:                                        causative      concepts    can   be    linked   to
                                                           instruments. The domain for this derivation
      Place is a semantic feature that
                                                           can be defined by identifying all instrumental
interacts with action core meanings to
                                                           actions as one class. However, identifying an
derive, without any reference to a particular
                                                           action as an instrumental one is a matter of
place, concepts that describe places in which
                                                           the synchronic usage of the speakers of the
actions are contained.
language, and hence, cannot be predicted in           commonplace machines growing, Modern
advance.        Nevertheless,     applying     this   Standard Arabic (MSA) tends to restrict this
derivation to causative actions can be used to        derivation to one form which becomes more
suggest certain derivation realised by words          productive by time, that is      fa”alt). Below
that satisfy the needs for new instrumental
                                                      we give a definition for machine as a semantic
terminology.
                                                      feature:

      Traditional       studies        associate
                                                            Machine is a semantic feature that
instruments with three moulds that are
                                                      applies to causative action to describe a
derived from the causative stems represented
                                                      machine that involves either external power
by mould I, namely,         mifal,           mif‟al
                                                      (such as electricity) or a considerable
and        fa”alat). We, on the other hand,           amount of force when performing an action
associate instruments with the first two
                                                            Machine, as we define it, is associated
moulds. The remaining mould describes, for
                                                      with the mould          faӋlt) which we will
us, a different semantic feature which we
describe later. The moulds with which we              link to mould II but not to mould I (as
associate instrument are linked to             the    suggested by some traditional studies) due to
derivation of verbs under the first mould             the force property expressed by machine

(mould I). For example,              miftah), “a      concepts.   Examples of this derivation are
                                                      found in words such as:       sayyãrat”a car”,
key” is linked to the concept realised by
                                                          Tayyãrat”an "an aircraft",        gassalat
fataha) "to open". Similarly,          miqbad )
                                                      "a washing machine") which are linked to
"a Handle") is linked to the default concept
                                                      intensified concepts derived from      sayyãra
realised by (    ..qabada) "to grasp").
                                                      “to walk/move ,           Tayyãra "to fly",

3.3 Machine                                              gassãla "to wash).

                                                      4 The Computational Model
      Traditionally, machine noun derivation
                                                            in this section we discuss how semantic
is considered to be part of instrument
                                                      interactions expressed by Arabic derivation
derivation. However, with the number of
                                                      can be organised as a semantic network that
support Arabic lexicalisation.               Semantic             of semantic networks known as taxonomic
interactions motivated by derivation as we                        organisations.
describe above, can be expressed into two
                                                                         A taxonomy is a semantic network that
layer semantics. An outer layer dealing with
                                                                  organises knowledge according to its level of
the semantic features associated with moulds
                                                                  generality.   In order to do this, a network
and an inner layer dealing with core meaning.
                                                                  defines some links that relate more specific
The outer layer semantic features, in our
                                                                  classes (represented by nodes at some level of
domain (i.e, terminology derivation), are
                                                                  the    network)    to     more      general   ones
place, instrument and machine.                   These
                                                                  (represented by nodes at higher levels).
features need to interact with action concepts
                                                                  Accordingly, the more specific classes are
(causative and cause neutral).                  Action
                                                                  said to inherit information from the more
concepts, in turn, are formed by means of
                                                                  general classes and the more general classes
interactions between action as an outer layer
                                                                  are said to subsume the more specific ones.
semantic feature and core meanings as inner
                                                                  For example, we could organise our domain
layer   representations,         These        semantic
                                                                  in    a taxonomy to         express     the above
interactions can be organised as a special type
                                                                  relationships as in Figure 3. 1.:




                                                          Thing



                         Situation                                              Core-meaning



        Instrumental-situation                                                  Action-core



                       Place-situation

                                              Action          Causative-core              cause neutral

          Machine-situation

                                     Intensified-action       Internally-caused-action




                                     Figure 3. 1: A prototype taxonomy
In Figure 3. 1, the topmost class is thing          properties from other classes based on its
which subcategorises for two subclasses:            subsumption relation These properties, in our
Core-meaning and Situation. Core-meaning            case, include linguistic properties such as
subsumes inner layer semantic classes while         moulds and roots.
Situation   subsumes     outer   layer   classes.
                                                    4.1 Choice of Formalism
Moreover, Situation is a general class that
interface our domain with the external world              In order to implement lexicalisation
where every derivation in our domain is             based on derivation we looked at various
linked to this class. For example an action         lexical   formalisms     and     explored    the
concept is subsumed by Situation (e.g, the          usefulness of these formalisms with regard to
concept expressed by               hassaba" to      Arabic derivation.       In general, lexical
                                                    representation formalisms can be classified
calculate" which is realised by mould
                                                    into unification-based systems inheritance-
  fa’ala). Similarly, the concept that is linked
                                                    based systems and those that combine both
to the action concept in the previous example
                                                    mechanisms.          Basic     unification-based
and focuses on machine derivation is also
                                                    formalisms do not provide a proper way to
subsumed by Situation (e-g., the concept
                                                    represent non-monotonic inheritance, which is
expressed by          hassabt which is realised     needed to eliminate redundancies in the
by mould       fa’’alat), as shown in Figure 3.1.   representation of semantic aspects of Arabic
                                                    derivation. Systems that are based only on
     In a taxonomy the subsumption relation         inheritance   mechanisms       have   limitations
permits the assimilation of new concepts into       when used to implement the two-layer
it In Knowledge Representation (KR) systems         semantics. Such systems do not support an
attempts have been made to allow the                automatic way to constraint derivation and do
automatic insertion of a given description into     not support automatic classification. When
a structured taxonomy. KL-ONE was the first         looking for a formalism for expressing the
system to allow the automatic classification        semantics of Arabic derivation, we suggest
of new concepts by assimilating them into the       that classification-based systems seem to be
taxonomy on the basis of their subsumption          the best available choice.       Classification-
relationships [Brachman85]. Once a concept          based systems are built around taxonomies
is assimilated in a taxonomy it inherits            and   integrate     knowledge     representation
mechanisms       such        default     and     multiple   identify role relations.     After this initial
inheritance, and structured relations such as               classification, role relations and the core
subsumption.           This integration allows for          meaning are used to build a general-input
expressive       representation           of      Arabic    class that is interpreted as an II class
derivation.      The reasoning mechanisms of                definition. The general-input class is used in
classification-based systems are based on                   another stage of classification to place the
classification         and      inheritance           The   input in the proper place in the situation
                                                            subtaxonomy. After classifying the general-
knowledge-base is easy to maintain and
                                                            input class, inference mechanisms are used to
modify if necessary.           In addition, semantic
                                                            reason about the surface realisation of the
descriptions can be efficiently mapped onto
                                                            classified input (using the inherited root and
language      specific       syntactic    and     lexical
                                                            mould).     Information resulting from this
representations.
                                                            classification process (the output of the proper
4-.2 Building the Generator                                 generation) is pawed on to the user-interface.
      The Generator for Lexemes in Arabic                   The output specifies morphological, syntactic
Derivation (GLAD) is implemented as a                       and semantic information for the classified
prototype to map disambiguated semantic                     input. Morphological information includes a
descriptions      to     Arabic        derived     words    root and an eligible mould.           Syntactic
[AlJabri97]. GLAD is composed of severed                    information describes syntactic arguments for
components a semantic disambiguator, a                      the classified concepts and their case-ending
user-interface, knowledge components and                    marks. Finally, semantic information names
an   automatic          classifier Of      these,     the   the parent(s) of the classified class in the
                                                            taxonomy.
semantic disambiguator is not implemented
and the automatic classifier is the I 1 classifier          4.3 Examples
[Reiter92]. The input to the system consists                      GLAD was originally designed and

of   semantic      descriptions          describing     a   implemented to generate Arabic derived

particular situation. The input specifies a core            words making a distinguish between actual

meaning and role specification sets for                     and potential words [Al-JABRI9]1.        Actual

situation participants. The classifier proceeds             words are those exist in the Arabic lexicon

by classifying role specification sets to                   and, in addition, their use is well established
                                                            by the speakers of the language.      Potential
words, on the other hand, are derived from             We tried GLAD with some semantic inputs
consonantal roots and we cannot judge their            (expressing the principles stated in this paper)
establishment in the language use. To do so            to show the possibility of generating now
we need to consult an MSA corpus. Such a               Arabic     terminology     from      disambiguated
corpus is, unfortunately, not available, The           semantic descriptions Some inputs and their
new Arabic terminology are potential words.
                                                       results     summarised     in      the      following:


Input                                                            Outputs
Core-meaning : rule-1                                            Mould                      root

Features : instrument- situation, action                                      Word

Core-meaning : wash-1                                             Mould                   Root

Features : instrument-situation, intensified-action.                          Word

                                           Table 4. 1: Example 1

                                                       well defined in a way the prevents ill-
        Table 4.1 shows the normal behaviour
                                                       derivation     from      taking      place     during
of the generator when disambiguated semantic
                                                       classification time.      When the first input
inputs are provided to generate actual words.
                                                       mentioned above is given to the generator it
These inputs include a description of a core
                                                       will be classified tinder causative action and
meaning (GLAD KB us" English verbs to
                                                       instrument situation at the same time. The
name core meanings that are associated with
                                                       mould for instrument will override any
roots, the number augmented to each verb
                                                       previous value and the inference mechanisms
indicates the corresponding sense as defined
                                                       will reason about the root.              This will be
in the WordNet [ Miller 95]), and a set of
                                                       followed      by    another       step     from    the
semantic features (usually linked to those
                                                       mechanisms to fill in the mould template
associated with moulds). The reader should
                                                       using root letters.    The result is a derived
note that the generator utilises a complex
                                                       word that describes an instrument. The same
knowledge-base which is different in its size
                                                       process will repeated for the second input.
from what      we have here.          Semantic
                                                       However, the second input describes a more
restrictions in the original knowledge-base are
specific type of instrument than the first one.           machine.     The, root in this case will be
This    is   due   to   the   introduction     of         mapped to the mould that is associated with
intensification in its set of semantic features.          machine     derivation                 faӋlat).
Accordingly, it will be classified under




   Input                                                        Outputs
   Core-meaning : mince-1                                            Mould:             root:

   Features : instrument- situation, action                            Word:

   Core-meaning : mince-1                                            Mould:             Root:

   Features : instrument-situation, intensified-action.                Word:

   Core-meaning : cut-1                                              Mould:             root:

   Features : instrument- situation, action                            Word:

   Core-meaning : cut-1                                              Mould:            Root:

   Features : instrument-situation, intensified-action.                Word:

                                             Table 4. 1: Example2

                                                          linked to      two possible core meanings
       Examples in Table 4.2 are meant to test
the generator with inputs that aim to generate            associated with two roots, namely,           frm

possible terminology for new concepts appear              and         q t „) which appear in the two
in other languages such as the one realised by
                                                          Arabic verbs        farama) "to mince" and
the English word shredder. To do so, we
need to suggest a core meaning that is linked             qata‟a) "to cut". In addition, we associate

to a consonantal root. Moreover, semantic                 each core meaning in the input with two sets

features need to be mentioned in the input in             of semantic features characterised by the

order to allow the derivation of a possible               presence/absence of intensification.         The

mould. In Table 4.2 the specified concept is              output shows four different possibilities
expressed as derived words. However, the               semantic specification of Arabic derivation
concept     realised    by the     English     word    can be exploited to states links between
shredder involves considerable amount of               semantic descriptions and derived words in
force and external power. This means that we           their final forms.
should exclude inputs that do not indicate
intensification.       Accordingly, The correct               The system we proposed in this paper is

derivation can be achieved through mould               meant      to    generate     Arabic      terminology.

           fa'ãlat machine derivation.          The    Arabic derivation provides the means for
                                                       mapping         technological       concepts      under
usefulness of core meanings suggested for this
                                                       specific subjects into certain moulds.               We
derivation should be left to the speakers'
                                                       briefly    discussed        the     specifications   of
common-sense or, alternatively, should be
                                                       semantic features motivated by these moulds.
judged by consulting a modern corpus.
                                                       We demonstrated our approach by some
5 Conclusions                                          examples from a generator that is designed
      In this paper we introduced a new                and implemented based on semantic aspects
approach to Arabic lexicalisation that is based        of Arabic derivation.
on derivation. We argued that Arabic has a
morphology that is different from that of                     The arguments introduced in this paper

English and existing lexicalisation techniques         open      the     door      towards      a   thorough

are   not    necessarily useful      for     Arabic.   investigation of semantic aspects of Arabic

Derivation in Arabic is a major word-                  derivation.       Such aspects, when carefully

formation process that associates derivational         studied will benefit the process of generating

processes with semantic features.             These    Arabic      terminology           and   enhance      the

features       interacts      with         meaning     performance of systems that implement

representations        expressed     by      Arabic    semantic mapping such as NLG and MT

consonantal roots---core meanings.              The    systems.
6 References


   [84             ]                                        [Dressler85] W. Dressler, Morphology : the
             1984                                             dynamic of derivation, Karoma Publishers,
                                                              Inc., Ann Arbor, USA, 1985.
   [76         ]
                                                             [Goldman75]          N. Goldman, conceptual
      1976                                                    generation, In R. Schank, editor, Conceptual In
                                                              formation     Processing,     North         Hoand,
   [Al-Jabri97]             S Al-Jabri, Generating
                                                              Amsterdam, 1975.
    Arabic Words from Semantic descriptions,
    Ph.D thesis, Edinburgh Univ., Edinburgh,                 [Horacek87] H. Horacek, Choice of words in
    UK, 1997.                                                 the generation process of natural language
                                                              interface. Applied artificial intelligence, I-
   [Bateman91]              J.    Bateman,         The
                                                              117-132, Hemisphere Publishing, Washington.
    theoretical status of ontologies in natural
                                                              D. C., USA, 1987,
    language processing, In susanne \peru and
    Brite Schmitz, editors, proceedings of the               (McKeown88]          K. Mckeown and W.
    workshop on Text Representation and Domain                Swatout,      Language      generation         and
    Modelling-Ideas from Linguistics and Al,                  explanation. In M. Zock and G. Sabah editors,
    University of Berlin KIT Report 97, October               Advances     in   Natural     Generation,      An
    9th – 11th, 1991,                                         Interdisciplinary Perspective, volume 1, Pinter,
                                                              London, 1988.
   [Bateman95] J. Bateman. R. Hensschel, and
    F.Rinaldi, The generalized upper model 2.0,              [Miller95] G. Miller, WordNet: A lexical
    GMD/IPSI Project KOMET, Germany, 12                       database for English, Communications of the
    1995.                                                     ACM, pages 39-41, November 1995.

   [Brachman85]             R.   Brachman    and    J.      [Micolov96) N. Nicolov, C, Mellish and G.
    Schmolze.           An overview of the KL-ONE             Ritchie. Approximate Generation from Non-
    knowledge representation system, Cognitive                Hierarchical Representations. In Donia Scott-,
    Science, 9-.171 216,1985,                                 editor,     Proceedings      of       the      8th
                                                              INTERNATIONAL Workshop on Natural
    Language Generation, Herstmonceux Castle,                          Artificial Intelligence Review, 8:309-366,
    UK, 13-15 June, 1996.                                              1995

   [Nirenburg88]                S.     Nirenburg      and    I.      [Thompson77]          H. Thompson, Strategy
    Nirenburg, A framework for lexical selection                       and tactics: A model for language production,
    in natural language generation. In Proceedings                     In Papers from the 13th Regional Meeting,
    of      the     12th        International       conference         Chicago Linguistic Society, pages 651-668,
    onComputational Linguistics, pages 471-475,                        Illinois, 1977.
    Budapest, 1988 (COLING-88).
                                                                      [Wood9l]      W.     Wood,       Understanding
   [Nogier92] J. Nogier and M. Zock, Lexical                          subsumption and taxonomy, In J. Sowa, editor,
    Choice as Pattern Matching, In Timothy E.,                         Principles of Semantic Networks, pages 45-94,
    Nagle Janice A., Nagle Laurie L. Gerholz and                       Morgan Kaufmann Publishers, fNC., San
    Peter     W.,     Eklund,           editors,    Conceptual         Mateo, California, USA, 1991.
    Structures: Current research and Practice, Ellis
                                                                      [Wood92]      W. Wood, The KL-ONE family,
    Horwood Series in Workshops, pages 413-436,
                                                                       In F. Lehmann, editors, Semantic Networks in
    Ellis Horwood Limited, London, England,
                                                                       Artificial   Intelligence,    Pergamon    Press,
    1992.
                                                                       Oxford, 1992.
   [Reiter92]       E. Reiter, C. Mellish and J.
                                                                      [Wright75] W. Wright, A Grammar of the
    Levine.        Automatic generation of online
                                                                       Arabic Language, Cambridge University, UK,
    documentation          in     the     Idas     project,   In
                                                                       1975,
    Proceedings of the third Conference on
    Applied         Natural        Language         processing
                                                                      [Zock9O]      M.   Zock.        La    génération
    (ANLP), pages 64 - 71, 1992.
                                                                       interactive de langage : comment visualiser le
                                                                       passage de l’idée à la phrase., In J. Anis and J.
   (Reiter94]       E. Reiter, Has Consensus NL
                                                                       Lebrave, editors, Text et ordinateurs: guistique
    Generation Architecture Appeared, and is it
                                                                       de Paris X, Nanterre, 1990.
    Psychologically Plausible, In the Proceedings
    of the 7" International Workshop on Natural
    Language         Generation,           pages       163-170,
    Kennebunkport, Maine, U.S, 21-24 June 1994.

   [Stede95]        M.      Stede,       Lexicalisation      in
    natural       language       generation,       A    survey,

				
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