SuhelJaber1andRodolfoDelmonte1
                                                                          
                                  1
                                   UniversityCa'Foscari,Dept.LanguageSciences,LaboratoryComputationalLinguistics,
                                                    Ca'Bembo,Dorsoduro1705,30123Venezia,Italy
                                                              {jaber,delmont}@unive.it
                                      
InthispaperweproposeanewapproachtothedescriptionofArabic
                                      morphologyusing 21tape finite state transducers, based on a particular and
                                      systematic use of the operation of composition in a way that allows for
                                      incrementalsubstitutionsofconcatenatedlexicalmorphemespecificationswith
                                      their surface realization for non1concatenative processes (the case of Arabic
                                      templaticinterdigitationandnon1templaticcircumfixation).
                                      	Arabic,morphology,non1concatenative,finitestate,composition.
                               		
                                 InthispaperweproposeanewapproachtothedescriptionofArabicmorphology
                               using21tapefinitestatetransducers,basedonaparticularandsystematicuseofthe
                               operation of composition in a way that allows for incremental substitutions of
                               concatenatedlexicalmorphemespecificationswiththeirsurfacerealizationfornon1
                               concatenative processes (the case of Arabic templatic interdigitation and non1
                               templaticcircumfixation).Thenwecompareitwithwhatinouropinionrepresentsthe
                               state1of1the1art among the 21tape finite1state implementations, that of Xerox [1],
                               which is mainly based on the operation of intersection. We intentionally limit
                               ourselves to the evaluation of 21tape strictly finite1state implementations for this
                               paper,leavingoutn1tapeimplementationssuchas[2]and[3],andthosebasedon
                               extendedfinite1stateautomata,suchas[4].Inanycasewebelievethatourapproach
                               couldbetriviallyadaptedton1tapeimplementationsaswell.
                                 Inthispaperwearguethat:
                                 
                               1.
theuseofcompositionallowstoovercomecertaintechnicalproblemsinherentto
                                 theuseofintersection;
                               2.
themethodofincrementalsubstitutionsthroughcompositionsallowsforanelegant
                                 description of all main morphological processes present in natural languages
                                 includingnon1concatenativeonesinstrictfinite1stateterms,withouttheneedto
                                 resorttoextensionsofanysort;
                               3.
ourapproachallowsforthemostlogicalencodingofeverykindofdependency,
                                 including traditional long1distance ones (mutual exclusiveness), circumfixations
                                 andidiosyncraticrootandpatterncombinations;