The research focuses on automatic construction of multi-lingual domain-ontologies, i.e., creating a DAG (directed acyclic graph) consisting of concepts relating to a specific domain and the relations between them. The domain example on which the research performed is “Organized Crime”. The contribution of the work is the investigation of and comparison between several data sources and methods to create multi-lingual ontologies. The first subtask was to extract the domain’s concepts. The best source turned out to be Wikepedia’s articles that are under the catgegory. The second task was to create an English ontology, i.e., the relationships between the concepts. Again the relationships between concepts and the hierarchy were derived from Wikipedia. The final task was to create an ontology for a language with far fewer resources (Hebrew). The task was accomplished by deriving the concepts from the Hebrew Wikepedia and assessing their relevance and the relationships between them from the English ontology.

This paper presents a method for compiling a large-scale bilingual corpus from a database of movie subtitles. To create the corpus, we propose an algorithm based on Gale and Church’s sentence alignment algorithm(1993). However, our algorithm not only relies on character length information, but also uses subtitle-timing information, which is encoded in the subtitle files. Timing is highly correlated between subtitles in different versions (for the same movie), since subtitles that match should be displayed at the same time. However, the absolute time values can’t be used for alignment, since the timing is usually specified by frame numbers and not by real time, and converting it to real time values is not always possible, hence we use normalized subtitle duration instead. This results in a significant reduction in the alignment error rate.

Computational lexicons are among the most important resources for natural language processing (NLP). Their importance is even greater in languages with rich morphology, where the lexicon is expected to provide morphological analyzers with enough information to enable themto correctly process intricately inflected forms. We describe the Haifa Lexicon of Contemporary Hebrew, the broadest-coverage publicly available lexicon of Modern Hebrew, currently consisting of over 20,000 entries. While other lexical resources of Modern Hebrew have been developed in the past, this is the first publicly available large-scale lexicon of the language. In addition to supporting morphological processors (analyzers and generators), which was our primary objective, thelexicon is used as a research tool in Hebrew lexicography and lexical semantics. It is open for browsing on the web and several search tools and interfaces were developed which facilitate on-line access to its information. The lexicon is currently used for a variety of NLP applications.

Most words in Modern Hebrew texts are morphologically ambiguous. We describe a method for finding the correct morphological analysis of each word in a Modern Hebrew text. The program first uses a small tagged corpus to estimate the probability of each possible analysis of each word regardless of its context and chooses the most probable analysis. It then applies automatically learned rules to correct the analysis of each word according to its neighbors. Finally, it uses a simple syntactical analyzer to further correct the analysis, thus combining statistical methods with rule-based syntactic analysis. It is shown that this combination greatly improves the accuracy of the morphological analysis—achieving up to 96.2% accuracy.