Multilingual access modalities to legal resources based on semantic disambiguation

An effective access to multilingual legal materials is strictly linked to the peculiarities of legal language as a technical language closely related to the diverse legal systems. This paper proposes an approach for a coherent cross-language information retrieval system based on semantic document indexing able to contextualize queries for terms disambiguation and translation. 1 Multilingualism in the law domain: an overview Today there is a strong need for worldwide sharing of legal information as internationalization and increasing globalization of market economy and social patterns of life have created a situation where the need for legal information from foreign countries and from different legal systems is greater than ever before. Such requirement is not new, but it is getting increasingly complex to meet under the pressure of the rapid cross-border transactions occurring between people of different legal cultures and languages. It is no doubt that the exchange of information is largely dependent on language, to be intended not only as a system of symbols, but also as a mean of communication [1], a tool for mediating between different cultures. As regards the language of the law, such languages properties have a major impact on the exchange of legal information. CrossLanguage Information Retrieval (CLIR) refers to a functionality implying the ability of a system to process a query for information in any language, search a multi-language collection and return the most relevant documents. As such, CLIR offers a practical approach towards worldwide sharing of knowledge for its potential to make information accessible across language barriers. The difficult task to effectively access multilingual legal material through information retrieval systems is definitively to match and weight legal terms across languages [2]. This generally implies translating from the language of the query to that of the material to be found or viceversa, and addressing the problem of word disambiguation which is greatly increased when mapping over legal languages. In fact crossing the language barrier between search requests and documents implies facing the problems of the system-bound nature of legal terminology and devising methods to map concepts between different legal systems. It is a matter of fact that in the last decades research and developments on CLIR have progressed rapidly, important cooperative initiatives have been undertaken at international level1 and issues of multilingual querying, presentation and retrieval have been extensively tackled mainly in the area of general domain information. A rather limited number of studies and applications have been produced in domain-specific areas and cross-language retrieval of legal information has received limited attention. In a multilingual access environment information is searched, retrieved and presented effectively without constraints due to the different languages and scripts used in the material to be searched and in the metadata, that is descriptive and semantic information allowing the retrieval of indexed documents to be found. One main question arising in the context of CLIR of law material is how should the language barrier between the search requests and documents be crossed. This involves decisions about what to translate: search requests into the language of the documents or documents into the language of the request, or even both. Besides this fundamental question, one crucial issue regards the best approach to adopt in carrying out translation and how far translating terms can be successful when dealing with legal information. From a practical point of view the approach for large collections is usually based on the most economical method, consisting in simply translating the query at retrieval time into the document (or metadata) languages, although it would be possible to translate all of the documents into the query language. This presupposes that the query can be translated in a reasonably accurate fashion and that monolingual retrieval systems are available for all of the document languages. Although many experiments have been carried out in general domain information using query translation techniques, in the real world they pose a number of problems related to the need of contextualization and interpretation, which are increased in the law domain [3]. 2 Key components of cross-language legal information retrieval Retrieving information over languages implies facilities such as multiple language recognition, translation, manipulation of information of queries and documents, cross-language search and retrieval, display and merging of results [4]. Basically, these components reflect different sides of the problem of multilingual access, covering technical and linguistic aspects. In such a context the system-bound nature of legal terminology, the complexity of legal languages, legal translations issues and comparative law aspects are major issues having important implications for effective retrieval of law across languages. Legal translation is an essential function for cross-language retrieval systems. One major question concerns the translation strategy to be adopted in order to ensure that users access legal information independently of the language used in a query. The relation between law and language can significantly broaden the scope of legal translation theory. In fact, while it can be assessed that everyday language already implies a formalized way of communication, legal language introduces a supplementary system of formalisation [5]. Although legal translation demands precision and certainty, it is bound to use abstractions, whose meanings derive from particular changing cultural and social contexts. These contexts generate a certain degree of ambiguity, which increases when the legal cultures and systems are vastly different from each other. On a practical level the problems raised by legal translation are strictly connected with those related to the variety and diversity of legal systems and as such to comparative law. Retrieval systems to legal information across different legal systems represent a practical approach to the confrontation and exchange of legal cultures. The whole process of interaction between legal languages can be identified as finding equivalents across legal systems. If no acceptable equivalents can be found in the target-language, subsidiary solutions must be sought, such as no translation and use of source terms, paraphrasing, creating a neologism with explanatory notes. Pure linguistic problems are likely to be encountered due to legal false friends. Despite the difficulties in establishing the equivalence of legal concepts belonging to different legal systems, a compromise has been adopted in trying to favour the integration of diverse legal cultures, while respecting each national legal system. What is needed is the identification of a common ground, namely common legal concepts and facts which, although not perfectly coinciding with those belonging to other systems, are conceptually close. It is up to legal users, once the material has been examined, to perceive the differences and peculiarities which make these resources unique. It is to be underlined that this does not necessarily lead to noise or unsuccessful searches, but allows for a first-phase search in context, useful to give evidence of the existence or non-existence of a specific concept in other legal systems. 3 Towards solutions for multilingual retrieval of law Knowledge-based systems can greatly contribute to cross-language retrieval through the structure and function of thesauri and ontologies. In fact these tools have the potential to manage the complexities of terminology in language and provide conceptual relationships, ideally through an embedded classification/ontology [6]. In the domain of law efforts are starting to be made in this direction. These are represented for example by the Lexical Ontologies for Legal Information Sharing (LOIS) project [7], Jurwordnet [8], DALOS project [9] and by a number of linguistic tools like the Legal Taxonomy Syllabus (LTS), Eu1 For examples the terms “administrative tribunals” cannot be translated in French as “tribunaux administratifs”. The English word for the French tribunal is Court and the administrative tribunals are administrative commissions which are comparable, mutatis mutandis, to the French “autorits administratives indpendantes”. 2 The law lexicon is characterized by both taxonomic vertical and associative horizontal relations and it has been developed by the Institute of Theories and Techniques for Legal Information (ITTIG-CNR) 3 LTS consists of both a database and a software development within the European project “Uniform terminology for European Private Law” and is coordinated by the Dipartimento di scienze giuridiche of the University of Turin. Available at: http: //www.eulawtaxonomy. org/index_en. html rovoc Thesaurus and Jurivoc, the legal thesaurus of the Swiss Federal Court. But in practice, aligning law vocabularies of two or more languages is a hard process. Ideally a multilingual legal thesaurus should include all concepts needed in searching by any user in any of the source languages, but difficulties arise in making the systems of legal concepts the same for all languages as a different language often suggests a different way of classifying law material and a system needs to be hospitable to all of these. In such a context what cross language retrieval of legal information systems should manage is mapping each query term from the source language to its possible multiple equivalents in the target language. However each of these equivalents may have other meanings in the target language or may not have a precise equivalent, requiring to be mapped to broader or narrower terms, but this can lead to distorting the meaning of the original query. Multiple meanings can be disambiguated through