E nglish2 BSL : A Rule-Based System for Translating E nglish into B ritish S ign L anguage (2023)

Abstract: British Sign Language (BSL) is a complex language with its own vocabulary and grammatical structure, separate from English. Despite its long-standing and widespread use by Deaf communities within the UK, thus far, there have been no effective tools for translating written English into BSL. This overt lack of available resources made learning the language highly inaccessible for most people, exacerbating the communication barrier between hearing and Deaf individuals. This paper introduces a rule-based translation system, designed with the ambitious aim of creating the first web application that is not only able to translate sentences in written English into a BSL video output, but can also serve as a learning aid to empower the development of BSL proficiency.

## introduction british sign language (bsl) is a visual-gestural language that has been widely used by deaf foot_0 communities within the uk for hundreds of years. contrary to a common misconception, bsl is not merely a visual representation of english; it developed independently of the spoken language, resulting in its distinct vocabulary and grammatical structure. this is evidenced by the fact that despite both bsl and american sign language (asl) emerging in english-speaking countries, the two sign languages are mutually unintelligible, i.e., they share neither a grammar nor a lexicon @xcite . the british deaf association (2023) states that there are more than 87,000 deaf people in the uk whose first language is bsl. however, a significant lack of hearing people choosing to learn bsl has led to deaf communities experiencing considerable levels of social exclusion @xcite , exacerbated by "educational segregation" and a lack of access to health services and employment opportunities @xcite . research suggests that integrating bsl lessons and deaf awareness education into uk schools is highly beneficial, not only for deaf students but also for their hearing peers @xcite . this poses the question: how can learning bsl be made more accessible? modern technology has provided access to applications that can translate between numerous spoken languages in real-time. google translate foot_2 can instantly convert written english into over 100 different spoken languages from any smartphone or web browser. as well as being a convenient way to quickly facilitate communication between people who speak different languages, translation applications can also be used as a learning tool. @xcite discussed the use of google translate as a meaningful resource for learning english. however, there is no comparable application for translating written english into bsl. this gap forms the core motivation behind the development of the english-to-bsl translation system presented in this paper. our main contribution is the development of a translation pipeline that is comprised of a bespoke set of syntax-based rules created without the use of pre-existing templates. this unique rule-based translation system enables a user to input a sentence in written english and play a video showing the generated bsl translation. the translation output, which follows bsl grammar, is comprised of a series of sign videos, each representing a bsl gloss. 3 our systematic evaluation of the system demonstrated the success of the web application from both quantitative and qualitative perspectives. ## related work below, we provide a summary of previously proposed methods for translating written text to sign language. this is then followed by a review of tools for english-to-bsl translation. ## the bsl grammatical structure understanding the fundamental grammatical structure of bsl is imperative when attempting to perform sign translation. this section provides a brief overview of the linguistic features of bsl. each individual sign can be represented by a gloss. glosses are lexemes, meaning that they remain constant regardless of any modifications to the word in english. this is because bsl is agnostic to any inflectional changes. there are no tenses in bsl, thus the english words "eat", "eating" and "ate", for example, are all encompassed by the gloss "eat", and therefore share the same sign in bsl @xcite . notably, glosses can represent phrases or emotions as well as individual words. bsl developed independently of spoken english, so it naturally follows a different grammatical structure. @xcite analysed the observable grammatical structure of bsl and how it differs from spoken english. however, they note that due to a significant lack of research into the linguistic structure of bsl, there is no official codified grammar. despite this, through analysis of organic bsl communication, an overarching summation of the general structure of sentences in bsl grammar can be defined as: 'time-frame then topic then action or a comment'. for example, the english sentence "i ate a cake yesterday" becomes ["yesterday" (timeframe), "cake" (topic), "eat" (action)] in bsl. as one can observe, glosses in the bsl translation follow an order that is different from that of the tokens in the english sentence. it is also worth noting that certain english words are completely omitted in sign language; intermediary words like determiners, prepositions, and some pronouns do not have a corresponding bsl gloss. instead, the meaning of these words is expressed via contextual signs and facial expressions. in fact, context cues are crucial in comprehending bsl as a whole. for example, a 'thumbs up' sign can mean "good" or "fantastic" depending on the level of expression. mouthing specific words, such as nouns and verbs, whilst signing them is also useful, as lipreading is often necessary to discern between different words with similar signs. these nuances can be difficult to replicate via automated translation. ## methodology we decided to take a rule-based machine translation (rbmt) approach to english-to-bsl translation, whereby a human expert explicitly defines a set of rules @xcite . as well as not requiring large amounts of pre-existing data, rbmt systems often provide more control, as the structured design means that results are deterministic and errors are easier to identify (okpor, 2014). furthermore, rbmt promotes transparency and scalability, as explicit rules are more easily understood by humans and more rules can be added to improve quality and enhance system complexity. our proposed english-to-bsl translation ap-proach is based on a pipeline with three stages: pre-processing of written english input, rule-based translation and post-processing of output. this pipeline was developed iteratively, leveraging continuous research into the grammatical structure of bsl and personal proficiency in the language. ## the english2bsl web application in order to facilitate user interactivity and display the english-to-bsl translation generated by our rule-based system, a novel web application, en-glish2bsl, foot_11 was developed. the angular framework foot_12 was utilised in integrating the translation pipeline into the user interface. ## evaluation our english-to-bsl translation system was assessed using a combination of quantitative and qualitative evaluation strategies. ## conclusions and future work this paper describes the development of en-glish2bsl, a web application that translates written english into bsl in real time. it is underpinned by a rule-based machine translation approach that leverages the output of syntactic analysis, i.e., pos tags, and a set of handcrafted rules to determine the order in which glosses should appear in the bsl output. quantitative evaluation of our translation approach showed that it can obtain an accuracy of up to 90%. the english2bsl user interface displays bsl output in the form of a series of sign videos seamlessly put together, thus acting as an interactive tool for people who wish to build or improve their knowledge of bsl. a limitation of the proposed translation system lies in its reliance on curated dictionaries (e.g., lists of temporal expressions and commonly used token bigrams) as well the finite number of signs in the video collection. our future work will focus on expanding our dictionaries and on incorporating more signs into the video collection. moreover, to broaden the reach of our translation tool, we will explore the development of a version of english2bsl that runs on mobile devices.