Prof. Dr.

Wrobel, Stefan

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  • Publication
    A logic-based approach to relation extraction from texts
    ( 2010)
    Horvath, Tamas
    ;
    Paaß, Gerhard
    ;
    Reichartz, F.
    ;
    Wrobel, Stefan
    In recent years, text mining has moved far beyond the classical problem of text classification with an increased interest in more sophisticated processing of large text corpora, such as, for example, evaluations of complex queries. This and several other tasks are based on the essential step of relation extraction. This problem becomes a typical application of learning logic programs by considering the dependency trees of sentences as relational structures and examples of the target relation as ground atoms of a target predicate. In this way, each example is represented by a definite first-order Horn-clause. We show that an adaptation of Plotkin's least general generalization (LGG) operator can effectively be applied to such clauses and propose a simple and effective divide-and-conquer algorithm for listing a certain set of LGGs. We use these LGGs to generate binary features and compute the hypothesis by applying SVM to the feature vectors obtained. Empirical results on the ACE--2003 benchmark dataset indicate that the performance of our approach is comparable to state-of-the-art kernel methods.
  • Publication
    Text mining and multimedia search in a large content repository
    ( 2009)
    Paaß, Gerhard
    ;
    Eickeler, Stefan
    ;
    Wrobel, Stefan
    Methods of acquiring, seeking and processing knowledge are a strategically vital issue in the context of globalized competition. One of the main subjects currently being researched is the development of semantic technologies that are capable of recognizing and classifying the content and meaning of information (words, pictures or sounds). In the context of the joint project CONTENTUS we show how different text mining techniques in a workflow are able to extract useful semantic information from text. In a comprehensive multimedia search engine these annotations together with text, metadata, and semantic clues extracted from multimedia documents (speech, music, video) may be used to give more focused access to information.
  • Publication
    Information and knowledge management
    ( 2009)
    Paaß, Gerhard
    ;
    Schneider, Daniel
    ;
    Wrobel, Stefan
    In recognition of knowledge as a valuable resource, there is a whole spectrum of processes, methods and systems for the generation, identification, representation, distribution and communication of knowledge, which aim to provide targeted support to individuals, organisations and enterprises, particularly in solving knowledge-based tasks. This is known as information management and knowledge management (which we will handle jointly in this article). Making the right knowledge available to the right people at the right time is considered a crucial factor in ensuring the efficiency and competitiveness of modern enterprises.