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Title Natural language semantics using probabilistic logic
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Date Accessioned
Discipline/Department Computer Sciences
University/Publisher University of Texas – Austin
Abstract With better natural language semantic representations, computers can do more applications more efficiently as a result of better understanding of natural text. However, no single semantic representation at this time fulfills all requirements needed for a satisfactory representation. Logic-based representations like first-order logic capture many of the linguistic phenomena using logical constructs, and they come with standardized inference mechanisms, but standard first-order logic fails to capture the “graded” aspect of meaning in languages. Other approaches for semantics, like distributional models, focus on capturing “graded” semantic similarity of words and phrases but do not capture sentence structure in the same detail as logic-based approaches. However, both aspects of semantics, structure and gradedness, are important for an accurate language semantics representation. In this work, we propose a natural language semantics representation that uses probabilistic logic (PL) to integrate logical with weighted uncertain knowledge. It combines the expressivity and the automated inference of logic with the ability to reason with uncertainty. To demonstrate the effectiveness of our semantic representation, we implement and evaluate it on three tasks, recognizing textual entailment (RTE), semantic textual similarity (STS) and open-domain question answering (QA). These tasks can utilize the strengths of our representation and the integration of logical representation and uncertain knowledge. Our semantic representation 1 has three components, Logical Form, Knowledge Base and Inference, all of which present interesting challenges and we make new contributions in each of them. The first component is the Logical Form, which is the primary meaning representation. We address two points, how to translate input sentences to logical form, and how to adapt the resulting logical form to PL. First, we use Boxer, a CCG-based semantic analysis tool to translate sentences to logical form. We also explore translating dependency trees to logical form. Then, we adapt the logical forms to ensure that universal quantifiers and negations work as expected. The second component is the Knowledge Base which contains “uncertain” background knowledge required for a given problem. We collect the “relevant” lexical information from different linguistic resources, encode them as weighted logical rules, and add them to the knowledge base. We add rules from existing databases, in particular WordNet and the Paraphrase Database (PPDB). Since these are incomplete, we generate additional on-the-fly rules that could be useful. We use alignment techniques to propose rules that are relevant to a particular problem, and explore two alignment methods, one based on Robinson’s resolution and the other based on graph matching. We automatically annotate the proposed rules and use them to learn weights for unseen rules. The third component is Inference. This component is implemented for each task separately. We use the logical form and the knowledge base…
Subjects/Keywords NLP; Machine learning; Probabilistic logic; MLNs; PSL; Markov Logic Network; QA; RTE; STS
Contributors Mooney, Raymond J. (Raymond Joseph) (advisor); Erk, Katrin (advisor); Gogate, Vibhav (committee member); Lifschitz, Vladimir (committee member); Ravikumar, Pradeep (committee member)
Language en
Country of Publication us
Record ID handle:2152/46617
Repository texas
Date Indexed 2018-10-22
Note [department] Computer Sciences;

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