This work aims to improve an N-gram-based statistical machine translation system between the Catalan and Spanish languages, trained with an aligned Spanish-Catalan parallel corpus consisting of 1.7 million sentences taken from El Periódico newspaper. Starting from a linguistic error analysis above this baseline system, orthographic, morphological, lexical, semantic and syntactic problems are approached using a set of techniques. The proposed solutions include the development and application of additional statistical techniques, text pre-and post-processing tasks, and rules based on the use of grammatical categories, as well as lexical categorization. The performance of the improved system is clearly increased, as is shown in both human and automatic evaluations of the system, with a gain of about 1.1 points BLEU observed in the Spanish-to-Catalan direction of translation, and a gain of about 0.5 points in the reverse direction. The final system is freely available online as a linguistic resource. solutions to solve these errors. Then, the improved system is carefully evaluated with respect to the baseline system and, finally, conclusions and future work are summarized in last section. Catalan and Spanish belong to the family of Romanic languages, also referred to as Romance or Latin languages. This family also includes other languages, such as French, Italian, Portuguese and Romanian, as it is comprised of all the languages descending from Vulgar Latin, which is, in turn, a branch of the Indo-European language family. Although the evolution of Latin into such Romanic languages occurred at all levels (phonological, morphological, lexical, etc.), the main characteristic of these languages is found at the syntactic level, with the loss of the declension system, which has led to a generalized use of SVO sentence structures with a large amount of prepositions. The Catalan language is spoken by more than nine million people distributed among Catalonia, the Valencian Community, the Balearic Islands, Andorra, and part of Aragon, Sardinia, Southern France and Murcia. On the other hand, Spanish is spoken by more than 400 million people as a native language in Spain and several countries in America, Asia and Africa. Spanish is the second most spoken language in the world after Mandarin Chinese. The main sociolinguistic characteristic of Catalan is the fact that it is found in a socially bilingual environment in all the regions where it is spoken: with Spanish in Spain (Catalonia, Aragon, Murcia) and Andorra, with French in South France and Andorra, and with Italian in Sardinia. This fact highlights the need for bilingual communication in all of these regions, where helping systems and resources have become increasingly popular and necessary. The translation system used in the current study -called N-II 1 -is an N-grambased SMT system developed at the Universitat Politècnica de Catalunya (UPC), trained with the aligned Spanish-Catalan parallel corpus taken from El Periódico 1 http://www.n-ii.org I I N I J J n n x n t t n ES: Nos los tenemos que creer, es lo único que nos falta. CA: Ens ho *tenim que creure, és l'únic que ens falta. We must believe it, it is the only thing we need. It has been seen previously that the verbal periphrasis tener que was translated as tenir que instead of haver de. However, when translating the Spanish form deber, which has the same meaning, the correct expression, haver de, is obtained, but the preposition de is usually missing: ES: Las islas Británicas (…) están teniendo unos meses de junio y julio extraordinariamente lluviosos y frescos por la continua entrada de borrascas atlánticas que, por estas fechas, deberían discurrir por latitudes mayores. CA: Les illes Britàniques (…) estan tenint uns mesos de juny i juliol extraordinàriament plujosos i frescos per la contínua entrada de borrasques atlàntiques que, per aquestes dates, * haurien [] transcórrer per latituds més grans. EN: The British Isles (…) are having unusually rainy and cool June and July months due to the continuous income of Atlantic squalls which, by these days, should be running at higher latitudes. Moreover, the preposition de is also elided when translating desde (from, since) to Catalan, obtaining des instead of des de: ES: Desde el neolítico hasta la actualidad hemos modificado profundamente las plantas y los animales silvestres. CA: *Des [] el período del neolític fins a l'actualitat hem modificat profundament les plantes i els animals silvestres. EN: Since the Neolithic Age era until now we have strongly modified the plants and wildlife. On the other hand, the preposition de falls in front of the conjunction que in Catalan, and this is normally not taken into account by the translator: ES: Tenías que acordarte de que hoy era el día. Havies de recordar-te *de que avui era el día. You should have remembered that today was the day.
In contrast, REF classify the errors that arise during Spanish-Catalan translation at several levels: orthographic, morphological, lexical, semantic and syntactic errors.
Overcoming statistical machine translation limitations: error analysis and proposed solutions for the Catalan---Spanish language pair
Language Resources and Evaluation
Computer Science