Fine-Grained Named Entity Recognition in Legal Documents

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Abstract

This paper describes an approach at Named Entity Recognition (NER) in German language documents from the legal domain. For this purpose, a dataset consisting of German court decisions was developed. The source texts were manually annotated with 19 semantic classes: person, judge, lawyer, country, city, street, landscape, organization, company, institution, court, brand, law, ordinance, European legal norm, regulation, contract, court decision, and legal literature. The dataset consists of approx. 67,000 sentences and contains 54,000 annotated entities. The 19 fine-grained classes were automatically generalised to seven more coarse-grained classes (person, location, organization, legal norm, case-by-case regulation, court decision, and legal literature). Thus, the dataset includes two annotation variants, i.e., coarse- and fine-grained. For the task of NER, Conditional Random Fields (CRFs) and bidirectional Long-Short Term Memory Networks (BiLSTMs) were applied to the dataset as state of the art models. Three different models were developed for each of these two model families and tested with the coarse- and fine-grained annotations. The BiLSTM models achieve the best performance with an 95.46 F $$_1$$ score for the fine-grained classes and 95.95 for the coarse-grained ones. The CRF models reach a maximum of 93.23 for the fine-grained classes and 93.22 for the coarse-grained ones. The work presented in this paper was carried out under the umbrella of the European project LYNX that develops a semantic platform that enables the development of various document processing and analysis applications for the legal domain.

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