Sign Language Representation for Machine Translation Sara Morrissey NCLT/CNGL Seminar Series 1 st April, 2009

Why is there no writing system? Social reasons Variation and demographic spread Political reasons Recognition Linguistic reasons Visual-gestural-spatial languages, simultaneous phoneme production

Implications of the lack of writing system …for Deaf people Forced use language not native …for the languages social acceptance  standardisation (Pizzuto, 2006) … for MT Limits availability of domain-specific corpora No standards, difficult to compare systems Significance of results on small datasets Difficult to use NLP tools developed for spoken langs

Sign Language Representation Formats Linear Stokoe Notation, HamNoSys Multi-level Gloss, Partition/Constitute, Movement- Hold, SiGML Iconic SignWriting

Linear Symbolic Notations Stokoe Notation: “don’t know” HamNoSys Notation: “nineteen”

Multi-level Representations Movement-Hold Partition/Constitute Gloss Annotation SiGML

Iconic Sign Writing

But different groups, different requirements (Pizzuto et al, 2006): the aspect of a language chosen for its representation, is largely dictated by the society and culture developing the writing system and what purpose and settings such communication is required for. Deaf, linguists, language processors…

Requirements for MT large bilingual domain-specific corpus of good quality digital data gold standard reference segmentation algorithms for separating words, phrases and sentences alignment methodologies for these units. searching the source and target texts acceptable capturing of the language for output

Discussion of current methods Stokoe (Stokoe, 1960) –Difficult to capture classifiers and NMFs –Decontextualised signs only –ASCII version (Mandel, 1993) HamNoSys (Prillwitz, 1989) –NMFs included –Subsection of 150 symbols for handwriting purposes –Mac usage, Windows font

Discussion of current methods (2) Gloss Annotation: (Leeson et al., 2006, Neidle et al., 2002) –Most commonly used in MT and by linguists –No universal conventions –Extensible –Using one language to describe another –Allows for simultaneous timed logging of features –Tools widely available –SL and linguistic knowledge a requirement –No knowledge of supplementary symbolic system required

Discussion of current methods (3) Partition/Constitute (Huenerfauth, 2005) –Captures movement, classifier and spatial info –Comprehensive, hierarchical rep’n –Implicit use of gloss terms Movement-Hold (Liddell & Johnson, 1989) –Numerically-encoded handshapes –Multi-layer –Used with recognition technology (Vogler & Metaxas, 2004)

Discussion of current methods (4) SiGML (Elliott et al., 2004) –Describes HamNoSys for animation (ViSiCAST) –Double representation SignWriting (Sutton, 1995) –Compact icons –Information displayed in one place –Advocated by SL linguists and growing Deaf –Not currently machine readable

Worked Example “Data-driven Machine Translation for Sign Languages” (Morrissey, 2008) MaTrEx MT system Glossed Annotations of Irish Sign Language (ISL) and German Sign Language (DGS) Air Traffic Information System corpus of ~600 sentences Translated and signed by native Deaf signers

Hand-crafted gloss annotation corpus

Translation Directions

MaTrEx Experiments ISL gloss-to-English text –Baseline –SMT –EBMT 1 –EBMT 2 –Distortion limit

ISL-EN MaTrEx Experiments BLEUWERPER Annotation Baseline SMT EBMT EBMT

EN-ISL MaTrEx Experiments BLEUWERPER ISL-EN best scores SMT EBMT EBMT

Other experiments ISL  DE, DGS  DE, DGS  EN –ISL  EN best scores, by 6.38% BLEU –EBMT 1 chunks improves for ISL-DE only –EBMT 2 chunks improves for ISL-DE only DE  ISL, DE  DGS, EN  DGS –EN  DGS best scores, by 1.3% BLEU –EBMT 1 chunks improves for EN  DGS & EN  ISL –EBMT 2 chunks improves for all Comparison with RWTH system –We’re better!  ~2-6% BLEU ISL video recognition Speech output

ISL Animation Poser software Hand-crafted 66 videos, 50 sentences Played in sequence 4 Deaf evaluators 2 x 4-point scale 82% - intelligibility 72% - fidelity Questionnaire Demo

Thesis Conclusions Good results can be obtained Glossing most appropriate, but not going forward –Allowed linguistic-based alignment –Linear, easily accessible format –Lack of NMF detail, time-consuming, not considered adequate representation of language EBMT chunks show potential but require more development Development of animation module

Where do we go from here? (the words are coming out all weird…) What is the most appropriate SL representation for MT? –Adequately represents the language, –Animation production, –Facilitates the translation process.

Rep’n overview, redux Glossing: machine readable, doesn’t adequately represent the language or facilitate animation Stokoe: ASCII version, not adequate rep’n Partition/Constitute: multi-layered, uses glosses Movement-Hold: multi-layered, uses glosses Sign Writing: compact icons, accepted, potential readability, not machine readable at present … HamNoSys & SiGML: machine readable, comprehensive description, adapted for animation, suited to SMT

The Future… Explore HamNoSys in practice MT in medical domain, Health Ireland Partner GP work group questionnaire Human Factors Minority Language MT

Thank you for listening Yep, it’s the end! I hope it wasn’t too long Any questions?