AN ONTOLOGY FOR A WEB DICTIONARY OF ITALIAN SIGN LANGUAGE Rosella Gennari KRDB, Free University of Bozen-Bolzano, Piazza Domenicani 3, 39100 Bolzano [email protected] Tania di Mascio University of L’Aquila, I-67040 Monteluco di Roio, L’Aquila [email protected] Keywords: ontology and the semantic web; knowledge management; web-based education. Abstract: Sign languages are visual languages used in deaf communities. They are essentially tempo-spatial languages: signs are made of manual components, e.g., the hand movements, and non-manual components, e.g., facial expressions. The e-LIS project aims at the creation of the first web bidirectional dictionary for Italian sign language–verbal Italian. Whereas the lexicographic order is a standard and ‘natural’ way of ordering hence retrieving words in Italian dictionaries, there is nothing similar for Italian sign language dictionaries. Stokoe- based notations have been successfully employed for decomposing and ordering signs in paper dictionaries for Italian sign language; but consulting the dictionaries requires knowing the adopted Stokoe-based notation, which is not as easy-to-remember and well-known as Italian alphabet is. Users of a web dictionary cannot be expected to be expert of this. There the role of ontologies comes into play. The ontology presented in this paper analyses and relates the formational components of a sign; in some sense, the ontology allows us to ‘enrich’ the e-LIS dictionary with expert information concerning classes of sign components and, above all, their mutual relations. We conclude this paper with several open questions at the intersection of knowledge representation and reasoning, semantic web, sign and computational linguistics. 1 INTRODUCTION was already in progress, it was realised that potential users of a web dictionary would also be non-experts Sign languages are visual languages used in deaf of Italian sign language. Then the idea of an ontol- communities, mainly. They are essentially tempo- ogy and the associated technology for the dictionary Section 3 spatial languages, simultaneously combining shapes, took shape. We explain our ontology in , and Section 4 Section 5 orientations and movements of the hands, as well as comment on it in . outlines the ar- non-manual components, e.g., facial expressions. A chitecture of the ontology-driven dictionary, and the Section 6 sign language and the verbal language of the coun- role that our ontology plays in it. In , we try of origin are generally different languages. The compare our ontology-driven dictionary to other elec- Section 7 creation of an electronic dictionary for Italian sign tronic dictionaries for sign languages. con- language is part of the e-LIS project (E-LIS project, cludes this paper with an assessment of our work and 2004), which is lead by the European Academy of several open questions. Bozen-Bolzano. The project commenced at the end of 2004 with the involvement of the ALBA cooperative from Turin, active in deaf studies. Section 2 outlines 2 BACKGROUND the essential background on Italian sign language and the e-LIS project’s history. 2.1 Sign language and dictionaries Initially, the e-LIS dictionary from Italian sign language to verbal Italian was intended for expert A sign language (SL) is a visual language based on signers searching for the translation of an Italian sign. body gestures instead of sound to convey meaning. At the start of 2006, when the development of e-LIS SLs are commonly developed in deaf communities. They can be used to discuss any topic, from the simple and concrete to the lofty and abstract. Contrary to popular belief, SL is not universal; SLs vary from nation to nation; even more, SLs such as Italian sign language (LIS) have dialects of their own. LIS is not a visual rendition of Italian verbal language; LIS has a grammar, syntax and lexicon of its own, e.g., a word can be translated into more than one sign and vice versa (see Figure 1). As highlighted in (Pizzuto et al., 2006), SLs can be assimilated to verbal languages “with an oral-only tradition”; their tempo-spatial nature, essentially 4- dimensional, have made it difficult to develop a writ- ten form for them. “However” — as stated in (Piz- Figure 1: Sign for Italian expression Parlare dietro le spalle, as in (Radutzky, 2001). zuto et al., 2006) — “Stokoe-based notations can be successfully employed primarily for notating single, 1 decontextualized signs” . As such, they are used to of current research, e.g., see (Garcia, 2006; Pizzuto transcribe signs and order them in (Radutzky, 2001), et al., 2006). We do not discuss this here for it goes a paper dictionary of LIS to Italian. beyond the scopes of our work which, at present, is of The transcription is based on a decomposition of experimental nature mainly. signs into so-called ‘formational units’. The fol- lowing classes correspond to the formational units 2.2 The e-LIS project adopted in (Radutzky, 2001): • the handshape class collects the shapes the The e-LIS dictionary is part of a research project lead hand/hands takes/take while signing; this class by the European Academy of Bozen-Bolzano (EU- alone counts more than 50 terms in LIS; RAC); e-LIS stands for dizionario Elettronico per la • the orientation class gives the the palm orienta- Lingua Italiana dei Segni (Electronic dictionary for tions, e.g., palm up; LIS). The project was conceived at the end of 2004 at • the movement of the hand/hands class lists the EURAC (E-LIS project, 2004). The ALBA coopera- movements of the hands in LIS; tive from Turin, active in deaf studies, was involved in • the location of the hand/hands class provides the the project for the necessary support and feedback on articulation places, i.e., the positions of the hands LIS. As clearly stated in (Vettori et al., 2004), most (e.g., on your forehead, in the air). sign language dictionaries form a hybrid between a Let us see an example entry of (Radutzky, 2001): the reference dictionary and a learner’s dictionary. On the sign for “parlare dietro le spalle” (to gossip behind contrary, the e-LIS dictionary is conceived a ‘semi- one’s back) in Figure 1 is a one-hand sign; the hand- bidirectional dictionary’, explaining LIS signs using shape is flat with five stretched fingers; as for the ori- LIS as meta-language and vice-versa. entation, the palm orientation is forward and towards The electronic format is particularly suited to an the left so that the hand fingers get in touch once with SL; for instance, it allows for videos and animations the location which is the neck; as for the movement of to be integrated in the dictionary and used to render the hand, this moves to the left only once. the movement of signs in space. Since the dictionary This information is readable in the transcription aims at reaching as many users as possible, it was con- ceived as a web application. in the upper-left corner of Figure 1 (namely, B⊥< Π ∗•). However, figuring out this information from the However the dictionary from LIS to verbal Italian transcription requires some expert knowledge of the was initially intended only for expert signers search- adopted transcription system and, above all, of the un- ing for the translation of a sign into verbal Italian. derlying formational rules of signs. Only subsequently it was realised that the potential Before proceeding further, a word on the written users of a web dictionary could also be non-experts representation of SLs is in order. The representation of LIS, willing to learn it; we cannot expect that they of SLs in written form is a difficult issue and a topic become expert of the transcription system outlined in Subsection 2.1 and, in particular, that they know how 1They were adopted for transcribing and ordering Amer- to compose the formational units of signs of that sys- ican signs in (Stoke et al., 1965). tem. Then, at the start of 2006, we commenced to work on a domain ontology (Guarino, 1998) for the LIS-to-Italian dictionary of e-LIS in order to repre- sent and make available to all such a knowledge. In the following Sections 3 and 4, we focus on the domain ontology at the core of our ontology-driven dictionary, whose architecture is outlined in Section 5. 3 THE DOMAIN ONTOLOGY The domain of our e-LIS ontology is the Stokoe-based classification outlined in Subsection 2.1 above. The ontology was constructed in a top-down manner start- ing from (Radutzky, 2001) with the expert assistance of linguists and deaf users of the e-LIS project (see Subsection 2.2). It was designed using the ICOM on- tology editor (Fillottrani et al., 2006). Note that our ontology is ‘richer’ than that clas- sification: the ontology introduces novel classes and relations among classes, thereby making explicit rel- evant pieces of information which were implicit and somehow hidden in that classification and in the ref- erence paper dictionary. For instance: it makes ex- plicit that each one hand sign is composed of at least one handshape by introducing an appropriate relation among the corresponding classes, One-hand sign and Handhsape; it groups together all the twelve different types of cyclic movements of hands in the Movement in circle class, not present in the paper dictionary. Figure 2: At the bottom: the ontology diagram. At the top: a snippet of the ontology diagram. See also the high- The current domain ontology in diagrammatic for- resolution version (E-LIS ontology, 2006). mat and a snippet of it are shown in Figure 2 (see also the high-resolution version (E-LIS ontology, 2006)).