An Application of Lexicalized Grammars in English ... - CiteSeerX

morpheme named Enclitic Particle in Persian that forces to attach aletter "i" to the end of a noun that is referred to by a relative clause.We extracted the value of this feature from all elementary treesrelated to the relative clauses; these trees are well-defined in theEnglish-Persian S-TAG notation.structure and order of Persian words. After these phases, all wordsare in their root form, which need to be inflected by the appropriatemorphological rules. For example, there is a morphological rulecalled "ezafe" that attaches the suffix "-e" to the end of the firstword of a compound NP.3.3 Morphological Rule ApplierSNPNPVPNPNPThe final phase of translation, which happened to be the simplestone, involves the application of Persian morphological rules. Afterperforming feature transformation, some modifications are appliedto individual words by using some morphological rules. The mainproperty of this phase is the locality of its action: each rule appliesonly to a single word, and does not affect the long distant words.We have implemented all those morphological rules that have beenexplained in [12].NP 0 ↓ VPNP 1 ↓V◊(α 1 )SNP 0 ↓ VPNP 1 ↓ ra(Fα 1 )(α 2 )Ν◊Ν◊NP ∗(β 1 )AUX◊VP ∗(β 2 )VPAUX◊VP ∗(Fβ 2 )4 A COMPLETE EXAMPLEIn this section, we introduce a complete example of English-Persian translation. The sentence pair is:(3) Our software solutions can create customized packages foryour special needsrah-ehal-ha-i narm-afzar-i ma mi-tavan-ad basteh-ha-ivizheh ra barai-e niaz-ha-i khas-e shoma tolid kon-adsolutions software our can packagescustomized for needs special your createBy applying a TAG-based parsing algorithm to the aboveEnglish sentence, the derivation tree shown in figure 4 is obtained.Each node of this tree refers to an elementary tree with its lexicalvalues associated to its anchor.The list of elementary trees with their associated Persianelementary trees is shown in figure 5 6 . For every elementary tree,the prefix letter F refers to its associated Persian one. Note that,there are usages of Noun and Adjective adjunctions in the auxiliarytrees β 1 and β 4 . The Persian forms of these trees are generated bychanging the order of their arguments. There is also a usage ofauxiliary verb in auxiliary tree β 2 . Persian supports these kinds ofcombinations with the same order and semantics. Prepositionadjunction can be handled by using the auxiliary tree β 3 . The word"ra" in the elementary tree Fα 1 , refers to a preposition that is usedafter objects of some verbs.Figure 5. English and Persian elementary trees used for sentence (3)V◊NP(Fα 2 )Ν◊NPNP ∗ (Fβ 1 )Ν◊NP ∗0 PPNP 1 ↓P◊(β 3 )NPNP ∗0 PPP◊NP 1 ↓(Fβ 3 )Α◊NP ∗(β 4 )NPNP ∗ (Fβ 4 )Α◊5 CONCLUSIONWe reported our implementation of an English-Persian translatorby using the S-TAG formalism. Although we focused ontranslation from English into Persian, the ideas of this paper canalso be applied to the reverse direction. However, the lake of acomprehensive computational grammar for Persian is the mainobstacle in this regard.In our experiments, we’ve used 860 sentences shorter than 16words. For English TAG, we’ve extended the XTAG data set afterselecting 150 elementary trees from the total number of 1227elementary trees, which have been used for parsing the samplesentences [17].By using the introduced transferred approach, we are now ableto translate all sentences with different syntactical structures suchas passive/active forms, and different tenses and persons.Although S-TAG seems to be a suitable method for syntacticand semantic transformation, the little information that is used inthe semantic interpretation of the context, makes it weak inencountering complex contexts. For example, there is no way todistinguish between the following sentences, by just using the S-TAG notion:β 1 [our]α 2 [solution]β 1 [software]α 1 [create]b2[can]β 1 [your]β 3 [for]α 2 [needs]α 2 [package]β 1 [special]β 4 [customized]Figure 4. The derivation tree of sentence "Our software solution cancreate customized packages for your special needs"Using the mentioned S-TAG, and by transforming thederivation trees shown in figure 5, we can derive the correct6 For simplicity, the Persian trees are shown in the reversed form (i.e., fromleft to right, similar to English).(4) "John asked a man"John az yek mard porsidJohn a man asked(5) "John asked a question"John yek soal ra porsidJohn a question askedThe difference between these two translated sentences is relatedto special prepositions associated with direct/indirect objects. InPersian the preposition "ra" appears after a direct object, whilesome others preposition such as "az" is placed before an indirectobject [4].ACKNOWLEDGEMENTSWe would like to thank the anonymous reviewers of the paper fortheir invaluable suggestions and comments. This work is partiallysupported by the Iranian Telecommunication Research Center(ITRC).