=Paper=
{{Paper
|id=Vol-2252/paper3
|storemode=property
|title=Statistical Machine Translation for Greek to Greek Sign Language Using Parallel Corpora Produced via Rule-Based Machine Translation
|pdfUrl=https://ceur-ws.org/Vol-2252/paper3.pdf
|volume=Vol-2252
|authors=Dimitrios Kouremenos,Klimis Ntalianis,Giorgos Siolas,Andreas Stafylopatis
|dblpUrl=https://dblp.org/rec/conf/ictai/KouremenosNSS18
}}
==Statistical Machine Translation for Greek to Greek Sign Language Using Parallel Corpora Produced via Rule-Based Machine Translation==
https://ceur-ws.org/Vol-2252/paper3.pdf
Statistical Machine Translation for Greek to Greek Sign
Language Using Parallel Corpora Produced via Rule-
Based Machine Translation
Dimitrios Kouremenos1, Klimis Ntalianis2, Giorgos Siolas3 and Andreas Stafylopatis4
1 School of Electrical & Computer Engineering
National Technical University of Athens
15780 Athens, Greece
dkourem@gmail.com
2 Department of Business Administration
University of West Attica
Athens, Greece
kdal75@gmail.com
3 School of Electrical & Computer Engineering
National Technical University of Athens
15780 Athens, Greece
gsiolas@islab.ntua.gr
4 School of Electrical & Computer Engineering
National Technical University of Athens
15780 Athens, Greece
andreas@cs.ntua.gr
Abstract. One of the objectives of Assistive Technologies is to help people
with disabilities communicate with others and provide means of access to in-
formation. As an aid to Deaf people, we present in this work a novel prototype
Rule-Based Machine Translation (RBMT) system for the creation of large qual-
ity written Greek text to Greek Sign Language (GSL) glossed corpora. In par-
ticular, the proposed RBMT system supports the professional translator of GSL
to produce high quality parallel Greek text - GSL glossed corpus, which is then
used as training data by the Statistical Machine Translation (SMT) MOSES [1]
application system. It should be noted that the whole process is robust and flex-
ible, since it does not demand deep grammar knowledge of GSL. With this
work we manage to overcome the two biggest obstacles in Natural Processing
Language (NLP) of GSL. Firstly, the lack of written system and secondly the
lack of grammar and finally we have been able to lay the foundations for an au-
tonomous translation system of Greek text to GSL. Evaluation of the proposed
scheme is carried out in the weather reports domain, where 20,284 tokens and
1,000 sentences have been produced. By using the BiLingual Evaluation Un-
derstudy (BLEU) metric score, our prototyped MT system achieves a relative
average score of 60.53% and 85.1%/65.5%/53.8%/44.8% for for 1-gram/2-
gram/3-gram/4-gram evaluation.
Keywords: machine translation, Greek, Greek Sign Language, GSL, Deaf peo-
ple communication, SMT, Moses, Phrase model.
2
1 Introduction
Translation helps people to communicate across linguistic and cultural barriers. How-
ever, according to Isabelle and Foster [2], translation is too expensive, and its cost is
unlikely to fall substantially enough, to constitute it as a practical solution to the eve-
ryday needs of ordinary people. Machine translation can help break linguistic barriers
and make translation affordable to many people. This situation is especially important
for Deaf people, since translation supports the communication between Deaf and
hearing communities and provides Deaf people with the same opportunities to access
information as everyone else [3].
1.1 Sign Languages – The Greek Sign Language
Sign languages (SLs) exploit a different physical medium from the oral-aural system
of spoken languages. SLs are gestural-visual languages, and this difference in modali-
ty causes SLs to constitute another branch within the typology of languages. Howev-
er, there are still many myths around SLs. One of the most common and enduring
myths is that the SL is universal; however, in reality, each country generally has its
own, native sign language [4, 5].
This paper focuses on the Greek Sign Language (GSL), which is a complete lan-
guage using the same grammar mechanisms incorporated by the oral language 1. Ac-
cording to the Greek law no. 2817/20002, GSL is the official language of the Greek
Deaf community3, while in 2013 the Greek Deaf Federation has published a formal
announcement demanding the institutional recognition of GSL 4. Currently more than
40,0005 people use GSL. Additionally, another common myth is that there is a corre-
lation between the Greek spoken language and GSL. However SLs do not derive from
spoken languages, but, as natural languages, they are influenced by their contact to
other languages, allowing the development of dialects and varieties [6].
1.2 Problems of SLs
According to Porta et. al. [6] regarding the fundamental problems of SLs, most con-
temporary works on SLs have adopted language theories created for the spoken lan-
guage instead of developing new theories. From the point of view of natural language
processing, SLs are still under-resourced or low-density languages – that is to say,
little or no specific technology is available for these languages, and computerized
linguistic resources, such as corpora or lexicons, are very scarce.
Additionally, another major problem of SLs is the lack of a writing system. Strictly
speaking, the only way to represent SLs is by using video and this is why there is lack
1 https://goo.gl/pAemOJ, https://en.wikipedia.org/wiki/Greek_Sign_Language
2 https://goo.gl/oItdK0
3 https://goo.gl/GGPIUo
4 http://www.omke.gr/anakoinwseis/diakirixi-syntagmatiki-anagnwrish-eng/
5 https://goo.gl/OZPAX5
3
of large corpora. The limitations in composing, editing and reusing SL utterances as
well as their consequences for Deaf education and communication have been system-
atically mentioned in the SL studies literature since the second half of the twentieth
century [7]. However, several notational systems exist. The most important include
Stokoe [8], SignWriting [9], HamNoSys [10] and Neidle [11]. SignWriting was con-
ceived primarily as a writing system, and has its roots in DanceWriting [12], a nota-
tion for reading and writing dance movements. HamNoSys was conceived as a pho-
nological transcription system for SLs, with the same objective as the International
Phonetic Alphabet (IPA) for spoken languages. A very promising system is SiGML
[13], which represents the 3-D properties of SLs. Last but not least, the “si5s” writing
system [14] has been proposed for the American Sign Language (ASL).
Furthermore, regarding GSL and to the best of the authors’ knowledge, currently
no Language Model exists. To confront the aforementioned problems, in this paper an
innovative RBMT system is proposed, which quickly produces high quality large
glossed GSL corpus. In particular, the focus is primarily on syntax, so glosses are
used instead of phonological notation. Glossing is a commonly used system for ex-
plaining or representing the meaning of signs and the grammatical structure of signed
phrases and sentences in a text, written in another language. However, glossing is not
a writing system that could be understood by SL users. For this reason, a novel gloss
system is proposed based on the Berkley system (for the ASL), which is also decorat-
ed with Non Manual Component Sign (NmCs) tag features. The proposed scheme
also enables the production of a simpler version of gloss without NmCs tags, adopted
from the Deaf Community and especially from the bilingual deaf people who use a
similar written Greek system in the Social Media.
To sum up the main innovations of the proposed scheme include:
The implemented GSL MT System is based on open source Toolkits.
The overall scheme, with the help of a professional translator, can produce differ-
ent kinds of large quality GSL Glossed Corpus that can be used for several purpos-
es.
The performance of the proposed GSL scheme is evaluated by the BLEU metric
score [15].
The rest of this paper is organized as follows: in Section 2 we present a sketch of GSL
and presets a review of Rule-based SL MT Systems. In Section 3 the related work is
analyzed and we describe how our prototyped RBMT system produces a parallel
Greek text with GSL glossed corpus and finally train the SMT Moses system. In
section 4 we evaluate the proposed SMT MOSES system. Finally, in section 5 con-
cludes this paper, providing also some directions for future work.
4
2 Literature review of SL MT systems
2.1 Background
Machine Translation (MT) of spoken languages has its roots in the 1940s, with a sig-
nificant expansion of interest in the late 70s and 80s [16]. A similar level of develop-
ment cannot be said for SL MT. Widespread research in this area did not emerge until
the 1990s, where linguistic analysis of SLs has appeared [17]. Despite this late ven-
ture, the development of SL MT systems has roughly followed that of spoken lan-
guage MT from ‘second generation’ rule-based approaches towards data-driven ap-
proaches. The ‘second generation’ or rule-based approaches to MT, emerged in the
1970s/1980s with the development of systems such as Meteo [18, 19] and Systran
[20]. These systems are examples of the first commercially adopted MT systems to
successfully translate spoken languages.
Fig. 1. The Vauquois Pyramid
Rule-based approaches may be sub-classified into transfer– and interlingua–based
methodologies. The Vauquois Pyramid, shown in Fig. 1. [21], is widely used in MT
circles to demonstrate the relative effort involved in translation processes. Transfer
approaches, being language-dependent, need to know the source and target languages.
Interlingua approaches tend to enact a deeper analysis of the source language sentence
that creates structures of a more semantic nature. Both methods have their advantages
and disadvantages.
2.2 Sketch of GSL
The most important documentation for a language is a reference grammar, which
documents the principles governing the construction of words and all kinds of gram-
matical structures found in a language. Currently and regarding GSL, there are some
attempts to gather resources, create a dictionary and annotated corpora and analyze a
5
set of signers’ data deriving from the annotated corpora [22, 23]. Additionally another
interesting initiative to develop the blueprint for SL grammars is carried out by the
SignGram COST Action6.
2.3 Rule-based SL MT Systems
All MT systems for SLs published up to 2003 were just works in progress or simple
demonstrators [24]. However, some systems were particularly distinguished, includ-
ing the ZARDOZ system [25], the ViSiCAST Translator [26], the ASL Workbench
[27], the SL translation via DRT and HPSG Safar et al. [28] and the TEAM project
Zhao et al. [29]. All these systems were rule-based and made use of transfer-based or
interlingua-based approaches. The only approach dealing with classifier predicates
was that of Huenerfauth [24], who proposed a multi-path approach combining inter-
lingua, transfer and direct approaches as a whole.
For Spanish to Spanish Sign Language (LSE), Baldassarri and Royo-Santas [30]
described a rule-based demonstrator. Spanish is analyzed using FreeLing dependency
analysis [31]. The dependency analysis through grammatical rules is transformed into
a series of glosses. The system was tested with 92 sentences containing a total of 561
words. Appropriate dictionary entries were created for the evaluation, with very satis-
factory results: 96% of the words were correctly translated, and 93.7% of them were
in correct order. Another interesting Spanish SL MT system is the rule-based Spanish-
to-LSE MT system based on Apertium, a free/open-source platform [32]. There are
no published results on this system but it is available online .
Now regarding GSL, Kouremenos et. Al [33], presented a prototype Greek text to
GSL conversion system. In that work, the detailed implementation of the language-
processing component is provided, focusing upon the inherent problems of knowledge
elicitation of sign language (SL) grammar and its implementation within a parser
framework. Recently Efthimiou et. al. [7] presented the implementation of a post-
processing stage to a grammar-based machine translation (MT) system from written
Greek to GSL.
2.4 Data-Driven Based SL MT Systems
Lately, example-based machine translation (EBMT), statistical machine translation
(SMT) and other types of data-driven machine translation systems have replaced the
earlier RBMT approaches. However, data-driven approaches estimate their parame-
ters from an aligned bilingual corpus, and their accuracy depends heavily on the
quality and size of this corpus. Unfortunately, corpora for SLs are still very far from
reaching the state-of-art of those for spoken languages. Additionally, the problem of
modality and the lack of a standardized writing system make data acquisition for SLs
a time-consuming and expensive task. Despite the lack of parallel corpora, the success
6 SignGram COSTS Action IS-1006 ‘‘A blueprint for sign language grammars—unravelling
the grammars of European sign languages: pathways to full citizenship of deaf signers and
to the protection of their linguistic heritage’’ (www.signgram.eu).
6
of data-driven approaches to MT between spoken languages, has led to the application
of the same techniques to SLs. However, according to Morrissey [34] , most research
in SL MT has emanated from sporadic and short-term projects as opposed to long
term research investment. Some works are still worth mentioning: the Thai-to-Thai
SL machine translation system [35] presents a direct translation system with reorder-
ing rules. The system for Thai reaches an F-score of about 97% for a set of 297 test
sentences. Bauer et. al. [36] presented the first statistical approach to SL MT for Ger-
man. In their paper they report that for 52 signs they achieve a recognition accuracy
of 94% and a score of 91.6% for 100 signs. Morrissey [17] presented exhaustive ex-
periments on the MaTrEx, a hybrid approach combining EBMT and SMT [37]. Re-
sults of MaTrEx on the ATIS corpus reached 0.39 BLEU for English-to-Irish Sign
Language translation, and about 50% for German to German Sign Language (DGS)
translation. Recently, Morrissey and Way [38] exploited the bidirectionality of the
MaTrEx system, demonstrating how additional modules, such as recognition and SL
animation, can potentially build a full SL MT model for spoken and SL communica-
tion.
2.5 Overall Discussion and Focus of the Proposed Scheme
This paper attempts to solve a very serious problem of the GSL, the lack of large GSL
corpora. Towards this direction, a processing methodology is proposed for creating
large quality parallel data for SLs by a human professional translator. The translator
uses a simple rule-based system based on Python, open source tools which incorpo-
rate a transfer module in case of interlingua approaches and a robust grammar tree
transfer parser. Next we feed the parallel corpus for training the Moses system, an
Open source toolkit for statistical machine translation [1].
All aforementioned components (except the open source tools) have been fully de-
veloped and extensively tested by the authors.
3 The Proposed MT System for Greek-to-GSL Translation
The proposed MT system has taken into consideration the Basic Unification Grammar
principles [1, 10, 39, 40]. For its overall development, different tools and technologies
have been combined for the prototype RBMT system : (a) AUEB’s POS Parser [41],
(b) the NLTK (Natural Language Toolkit) 3.0 suite , which is a free, open source,
community-driven, leading platform for building Python programs to work with hu-
man language data, (c) Java and (d) Perl scripts. And for the ST system we finally use
Moses, an open-source toolkit for statistical machine translation [1].
Additionally, translation by RBMT system is supervised by a professional transla-
tor, so that output texts are corrected and new transfer rules and lexicon mapping data
are added to the RBMT, so that any newly appearing cases (linguistic phenomena) are
covered.
7
3.1 Overall Architecture
The whole procedure of our system is divided into two main stages, (Fig. 1). Firstly,
we use our RMBT system to produce parallel corpora of Greek text and GSL gloss
text. At RBMT system we perform analysis actions separating by POS parsing is
carried out by AUEB’s Greek POS Parser [41] and chunk partial parsing (Fig. 3).
Table 1 provides a list of the fine most frequently appearing morphological tags of the
Parole standard. Chunk Partial Parser use the chunk parser and regular grammar from
Python’s NLTK Toolkit, Partial Chunking is accomplished and sentences are divided
into sub-sentences as constituency tree structure. Chunk Partial Parser use the chunk
parser and regular grammar from Python’s NLTK Toolkit, Partial Chunking is ac-
complished and sentences are divided into sub-sentences as constituency tree struc-
ture. Next we have the transfer action separating by chunk transfer and word transfer.
The Chunk transfer module incorporates a bilingual lexicon and specific knowledge
from the language pair-specific rule database to transfer the Greek constituency tree
structure into the corresponding GSL constituency tree structure. Then Gloss se-
quence and Gloss synthesis are performed to complement the structure, so that the
final sentence is formed.
The transfer module incorporates a bilingual lexicon and specific knowledge from
the language pair-specific rule database to transfer the Greek constituency tree struc-
ture into the corresponding GSL constituency tree structure. Word ordering and mor-
phological rules are applied to the transferred constituency tree, so that the output of
the generation stage of RBMT system is a sequence of written glosses with morpho-
logical and non-manual components’ indications. The proposed written GSL glosses
system uses the code style of BERKLEY Gloss System [42, 43] as a transcribing
system, which abstracts away the phonological representation of signs (Fig. 4). De-
tails of the different stages of the MT strategy are provided in the following subsec-
tions (Fig. 2)
8
text • Written Greek
• POS Tagging
Analysis (RBMT) • Chunk Partia Parser
• Chunk Transfer
Transfer (RBMT) • Word Transfer
• Word order generation
Generation (RBMT) • Morphological generation
• Gloss synthesis
• tokenazion
Parallel Corpus • truecasing
Preparation (SMT) • cleaning
Training the
• word alignments the paralle corpus
Translation System • language modeling training
(SMT)
Testing - Evaluation • blue score evaluation
(SMT)
Fig. 2. Architecture of the system
S
(NP Βροχές/NoCmFePlAc και/CjCo καταιγίδες/NoCmFePlAc)
(VB θα/PtFu εκδηλωθούν/VbMnIdXx03PlXxPePvXx)
(NP
κατά/AsPpSp
τόπους/NoCmMaPlAc
στη/AsPpPaFeSgAc
Δυτική/AjBaFeSgAc
Ελλάδα/NoPrFeSgAc)
(NP-CM Τα/AtDfNePlNm Χριστούγεννα/NoPrNePlAc)
)
Fig. 3. POS Parsed and Chunked Sentence
Table 1. TABLE I. Five most frequently appearing morphological tags of the parole stand-
ard.
POS Example Comment
Ουσιαστικό/Noun (No), γένους
Βροχές/tag=NoCmFePlAc
No θηλυκού/feminine (Fe) στον πληθυντικό/plural
(rain)
(Pl)
Επίθετο/Adjective(Aj), γένους
Δυτική/AjBaFeSgAc
Aj θηλυκού/feminine (Fe) στον ενικό/in singular
(Western)
(Sg)
9
στα/ AsPpPaNePlAc
As Adposition (= Preposition)7
(at)
τα/AtDfNePlNm Άρθρο/Article (At), γένος ουδέτερο/gender
At
(the) neutral (Ne) στον πληθυντικό/plural (Pl)
εκδηλωθούν/VbMnIdXx03PlXxPe
Ρήμα/Verb (Vb), παθητικής φωνής/passive
Vb PvXx
voice (Pv), πληθυντικός/plural (Pl)
(occurs)
The RBMT system, generates the sequence of GSL glosses decorated with non-
manual component tags, using code types of the BERKLEY Gloss system [42, 43]
and next after making corpus preparation actions, we have the parallel corpus (Fig. 4)
in order to train the Moses SMT system [1] at the last stage.
Written Greek (Source)
Βροχές και καταιγίδες θα εκδηλωθούν κατά τόπους στη Δυτική Ελλάδα τα
Χριστούγεννα . (Rain and thunderstorms will occur locally in western
Greece at Christmas.)
GSL Gloss text (export)
ΧΡΙΣΤΟΥΓΕΝΝΑ/CHRISTMAS/NoAcNePlXx
ΜΕΤΑ/after/Pt/ΧΛ(ΜΕΤΑ) ΓΙΝΕΙ/occur/Vb ΒΡΟΧΗ/rain/NoAcFePlXx
ΚΑΙ/and/Cj ΚΑΤΑΙΓΙΔΑ/thunderstorms/NoAcFePlXx/ΜΧ(ΕΝΤΑΣΗ/
INTENSITY) /ΜΓΛ(ΦΟΥΣΚΩΜΕΝΑ/BOOKED) ΑΝΤ_3/there/PreDict
/ΜΤ(ΑΝΟΙΧΤΑ/OPEN) ΤΟΠΟΣ/LOCALY/ΤΠΘ(Χ1)-
ΤΟΠΟΣ/LOCALY/ΤΠΘ(Χ2)/No
ΑΝΤ_3/THERE/PreDict/ΜΤ(ΑΝΟΙΧΤΑ/OPEN)
ΕΛΛΑΔΑ/GREECE/NoAcFeSgXx ΔΥΤΙΚΟΣ/WESTERN/AjAcFeSgXx
./PTERM_P
Fig. 4. Written Greek - Gloss Text
The parallel sentences, of RBMT system, are then word-aligned, typically using
GIZA++3, which implements a set of statistical models developed at IBM in the 80s.
These word alignments are used to extract phrase-phrase translations, or hierarchical
rules as required, and corpus-wide statistics on these rules are used to estimate proba-
bilities. Phrase-Based Models translate phrases as atomic units. The phrase-based
statistical machine translation model we present here was defined by Koehn et al.
[44]. See also the description by Zens [45].
An important part of the translation system is the language model, a statistical
model built using monolingual data in the target language and used by the decoder to
try to ensure the fluency of the output.
To estimate the phrase translation probability φ(e|f) we proceed as follows: First,
the extract file is sorted. This ensures that all English phrase translations for a foreign
phrase are next to each other in the file. Thus, we can process the file, one foreign
phrase at a time, collect counts and compute φ(e|f) for that foreign phrase f. To esti-
7 http://nlp.ilsp.gr/nlp/tagset_examples/tagset_en/adposition.html
10
mate φ(f|e), the inverted file is sorted, and then φ(f|e) is estimated for an GSL Gloss
phrase at a time (Fig. 5). By default, only a distance-based reordering model is in-
cluded in final configuration. This model gives a cost linear to the reordering distance.
$ grep 'πληροφορίες |' ./phrase-table | sort -nrk 7 -t\ | head
πληροφορίες ||| ΠΛΗΡΟΦΟΡΙΑ ||| 1 1 1 1 ||| 0-0 ||| 1 1 1 ||| |||
περισσότερες πληροφορίες ||| ΠΛΗΡΟΦΟΡΙΑ ΠΟΛΥΣ ||| 1 0.625 1 1 ||| 1-0
0-1 ||| 1 1 1 ||| |||
! περισσότερες πληροφορίες ||| ! ΠΛΗΡΟΦΟΡΙΑ ΠΟΛΥΣ ||| 1 0.511364 1
0.9 ||| 0-0 2-1 1-2 ||| 1 1 1 ||| |||
! ! περισσότερες πληροφορίες ||| ! ! ΠΛΗΡΟΦΟΡΙΑ ΠΟΛΥΣ ||| 1 0.418388
1 0.81 ||| 0-0 1-1 3-2 2-3 ||| 1 1 1 ||| |||
Fig. 5. Score Phrases
4 Evaluation of the MT System
Human evaluation is fundamental and remains crucial to proper assessment of the
quality of MT systems. When the output of an MT system is evaluated, however, the
accuracy of translation process is taken into account.
Initially, by performing text mining from several weather-related web pages8, we
have created a large parallel written Greek – GSL Gloss language corpus, consisting
of 1,015 sentences and 20,287 tokens. Next the corpus was divided into 2 sub-
corpuses (one of 100 sentences for evaluation and one large of 900 sentences for
training the SMT system). The whole procession translation by RBMT system is su-
pervised by a professional translator, so that output texts are corrected.
For measuring the translation accuracy of the proposed MT system, the Bleu Score
[15] for 1 to 4-gram is used.
Οur prototyped MT system achieves a relative average score of 60.53% and
85.1%/65.5%/53.8%/44.8% for for 1-gram/2-gram/3-gram/4-gram evaluation. Here it
should also be mentioned that the larger the n-gram the better the quality of transla-
tion. Nevertheless, we expect in the future to try to improve performance rates by
extending to larger corpora sizes and alternative algorithms of Moses Suite.
On the other hand, and for comparison reasons, it is worth noting that similar ex-
periments can be found in the literature. Kanis [46] in his work, the training set con-
sisted of 12,616 sentences, regarding Czech to Czech Sign Language. In these exper-
iments the proposed system reached a BLEU score of 0.81, a WER of 13.14% and a
PER of 11.64%. Similarly, in [47] and in case of German to German Sign Language
two experiments have been performed. In these cases, the BLEU and PER obtained
were 0.021 and 85.7% for the first experiment and 0.026 and 81.1% for the second
experiment respectively. However, the reported baseline with the open source toolkit
for statistical machine translation Moses [1] was 0.181 BLEU and a 71.0% TER with
a training set of 2,565 sentences and a test set of 512 sentences. By combining several
systems, they finally reached a BLEU of 0.234 and a TER of 65.5%. Here it should be
noted that the disparity between these results is because Czech and Czech Sign Lan-
8 http://www.deltiokairou.gr/, http://www.weather.gr/, http://meteo.gr/
11
guage have the same surface order, but German and German Sign Language do not.
Furthermore, results confirm that data scarcity and domain sparseness lead the data-
based approaches to perform worse than the rule-based systems. Providing bilingual
lexical resources has a positive effect in data-based approaches. We think that this
result should not be interpreted as domain independence. Instead, we consider that
data are not still enough to measure the out-of-domain effect. We think that this result
should not mean that GSL and Greek have similar word orders or that the order gen-
erated by the system is not valid. We consider that GSL order admits some degree of
freedom and that the order of signs in the learning corpus is also valid for the purpose
of communication. At this point, deeper and more extensive experiments, measuring
human understanding, should be performed to draw further conclusions.
5 Conclusions and future work
The choice of a particular type of technology to process a language is greatly influ-
enced by the density of the language, i.e., the availability of digitally stored resources.
Commercial research and development have concentrated on high-density languages.
Today GSL, like any other sign language, is a low-density or under-resourced lan-
guage. Because of modality, acquisition of sign language data is a time consuming
and expensive task, compared to the acquisition of spoken or written data. Currently
is maybe one of the first attempts of creating parallel corpus of sufficient size for
written Greek - GSL, which could enable data-driven approaches to machine transla-
tion in non-restricted domains. Additionally, the few existing works on the area of
creating and analyzing GSL Corpus are copyrighted and thus not open to the re-
searchers or the Deaf communities.
On the other hand, GSL, as all other SLs in the world, is not standardized, and
GSL’s full grammar has not been published yet. Only some recent works point out
important grammar points, lines and references [7, 33, 48]. All these problems make
the development of a RBMT system “supervised by a professional translator” the only
viable solution. In this case the translator will be enabled to create large, parallel,
quality, Greek to GSL corpus, without the need of grammar.
Finally, many other important aspects have not been addressed in this paper, and
there is still a great deal of work to do. In particular, the proposed system should be
tested using: (a) the factored Translation Model of Moses [1], (b) in other thematic
areas, by gathering large relevant corpus, and (c) in the field of SL synthesis (anima-
tion), using animation technologies and motion captures technologies in order to have
exports to a realistic animation motion of SL and speed up the creation of multimedia
dictionary database.
12
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