Browsing by Author "Grez, Alejandro"

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    A Formal Framework for Complex Event Recognition
    (2021) Grez, Alejandro; Riveros, Cristian; Ugarte, Martin; Vansummeren, Stijn
    Complex event recognition (CER) has emerged as the unifying field for technologies that require processing and correlating distributed data sources in real time. CER finds applications in diverse domains, which has resulted in a large number of proposals for expressing and processing complex events. Existing CER languages lack a clear semantics, however, which makes them hard to understand and generalize. Moreover, there are no general techniques for evaluating CER query languages with clear performance guarantees.
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    Automatic knowledge-graph creation from historical documents: The Chilean dictatorship as a case study
    (2024) Díaz, Camila; Dunstan Escudero, Jocelyn Mariel; Etcheverry, Lorena; Fonck Larraín, Antonia; Grez, Alejandro; Mery Quiroz, Domingo Arturo; Reutter de la Maza, Juan Lorenzo; Rojas, Hugo
    We present our results regarding the construction of a knowledge graph from historical documents related to the Chilean dictatorship period (1973-1990). Our approach uses LLMs to automatically recognize entities and relations between them and resolve conflicts between these values. To prevent hallucination, the interaction with the LLM is grounded in a simple ontology with four types of entities and seven types of relations. To evaluate our architecture, we use a gold standard graph constructed using a small subset of the documents, and compare this to the graph obtained from our approach when processing the same set of documents. Results show that the automatic construction manages to recognize a good portion of all the entities in the gold standard and that those not recognized are explained mainly by the level of granularity in which the information is structured in the graph and not because the automatic approach misses an important entity in the graph. Looking forward, we expect this report to encourage work on other similar projects focused on enhancing research in humanities and social science. However, we remark that better evaluation metrics are needed to accurately fine-tune these types of architectures.
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    Dynamic Data Structures for Timed Automata Acceptance
    (2022) Grez, Alejandro; Mazowiecki, Filip; Pilipczuk, Michal; Puppis, Gabriele; Riveros, Cristian
    We study a variant of the classical membership problem in automata theory, which consists of deciding whether a given input word is accepted by a given automaton. We do so through the lenses of parameterized dynamic data structures: we assume that the automaton is fixed and its size is the parameter, while the input word is revealed as in a stream, one symbol at a time following the natural order on positions. The goal is to design a dynamic data structure that can be efficiently updated upon revealing the next symbol, while maintaining the answer to the query on whether the word consisting of symbols revealed so far is accepted by the automaton. We provide complexity bounds for this dynamic acceptance problem for timed automata that process symbols interleaved with time spans. The main contribution is a dynamic data structure that maintains acceptance of a fixed one-clock timed automaton A with amortized update time 2(O(vertical bar A vertical bar)) per input symbol.