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6 Benchmarking Semantic Named Entity Recognition Systems

Named entity recognition (NER) became one of the most exploited means for information extraction and content enrichment. The NER systems detect text fragments identifying entities and provide classification of the entities into a set of pre-defined categories. This is usually a fixed set of raw classes such as the CoNLL set (PERSON, ORGANIZATION, LOCATION, MISCELLANEOUS), or classes from an ontology, such as the DBpedia Ontology. However, it is a recent trend that the NER systems such as DBpedia Spotlight to go beyond this type classification and also perform unique identification of the entities using URIs from a knowledge bases such as DBpedia or Wikipedia. During LOD2, we have created a collection of tools adhering to this new class of Wikification, Semantic NER or Entity Linking systems and contributed it the Wikipedia page about Knowledge Extraction[1].

While these Semantic NER systems are gaining popularity, there is yet no oversight on their performance in general, and their performance in specific domains. To fill this gap, we have developed a framework for benchmarking

NER systems [5][2]. It is developed as a stand-alone project on top of the GATE text engineering framework[3]. It is primarily developed for off-line evaluation

of NER systems. Since different NER systems might perform better in one and worse in another domain, we have also developed two annotated datasets with entities, the News and the Tweets dataset. The Tweets datasets, consists of very large number of short texts (tweets), while the News dataset consists of standard-length news articles.

A prerequisite for benchmarking different NER tools is achieving interoperability at the technical, syntactical and conceptual level. Regarding the technical interoperability, most of the NER tools provide a REST API over the HTTP protocol. At the syntactical and conceptual level we opted for the NIF format, which directly addresses the syntactical and the conceptual aspects. The syntactical interoperability is addressed using the RDF and OWL as standards for common data model, while the conceptual interoperability is achieved by identifying the entities and the classes using global unique identifiers. For identification of the entities we opted for re-using URIs from DBpedia. Since different NER tools classify the entities with classes from different classification systems (classification ontologies), we perform alignment of those ontologies to the DBpedia


In the future, we hope to exploit the availability of interoperable NIF corpora as described in [10].

  • [1] A frequently updated list can be found here Knowledge extraction#Tools
  • [2]
  • [3]
  • [4]
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