Old Content and Modern Tools : Searching Named Entities in a Finnish OCRed Historical Newspaper Collection 1771–1910

Named Entity Recognition (NER), search, classification and tagging of names and name-like informational elements in texts, has become a standard information extraction procedure for textual data. NER has been applied to many types of texts and different types of entities: newspapers, fiction, historical records, persons, locations, chemical compounds, protein families, animals etc. In general, the performance of a NER system is genre- and domain-dependent and also used entity categories vary [Nadeau and Sekine 2007]. The most general set of named entities is usually some version of a tripartite categorization of locations, persons, and organizations. In this paper we report trials and evaluation of NER with data from a digitized Finnish historical newspaper collection (Digi). Experiments, results, and discussion of this research serve development of the web collection of historical Finnish newspapers. Digi collection contains 1,960,921 pages of newspaper material from 1771–1910 in both Finnish and Swedish. We use only material of Finnish documents in our evaluation. The OCRed newspaper collection has lots of OCR errors; its estimated word level correctness is about 70–75 % [Kettunen and Pääkkönen 2016]. Our principal NE tagger is a rule-based tagger of Finnish, FiNER, provided by the FIN-CLARIN consortium. We also show results of limited category semantic tagging with tools of the Semantic Computing Research Group (SeCo) of the Aalto University. Three other tools are also evaluated briefly. This paper reports the first large scale results of NER in a historical Finnish OCRed newspaper collection. Results of this research supplement NER results of other languages with similar noisy data. As the results are also achieved with a small and morphologically rich language, they illuminate the relatively well-researched area of Named Entity Recognition from a new perspective.Peer reviewe

FiST – towards a Free Semantic Tagger of Modern Standard Finnish

This paper introduces a work in progress for implementing a free full text semantic tagger for Finnish, FiST. The tagger is based on a 46 226 lexeme semantic lexicon of Finnish that was published in 2016. The basis of the semantic lexicon was developed in the early 2000s in an EU funded project Benedict (Löfberg et al., 2005). Löfberg (2017) describes compilation of the lexicon and evaluates a proprietary version of the Finnish Semantic Tagger, the FST2. The FST and its lexicon were developed using the English Semantic Tagger (The EST) of University of Lancaster as a model. This semantic tagger was developed at the University Centre for Corpus Research on Language (UCREL) at Lancaster University as part of the UCREL Semantic Analysis System (USAS3 ) framework. The semantic lexicon of the USAS framework is based on the modified and enriched categories of the Longman Lexicon of Contemporary English (McArthur, 1981). We have implemented a basic working version of a new full text semantic tagger for Finnish based on freely available components. The implementation uses Omorfi and FinnPos for morphological analysis of Finnish words. After the morphological recognition phase words from the 46K semantic lexicon are matched against the morphologically unambiguous base forms. In our comprehensive tests the lexical tagging coverage of the current implementation is around 82–90% with different text types. The present version needs still some enhancements, at least processing of semantic ambiguity of words and analysis of compounds, and perhaps also treatment of multiword expressions. Also a semantically marked ground truth evaluation collection should be established for evaluation of the tagger.Peer reviewe

Corpus-Based Generation of Content and Form in Poetry

We employ a corpus-based approach to generate content and form in poetry. The main idea is to use two different corpora, on one hand, to provide semantic content for new poems, and on the other hand, to generate a specific grammatical and poetic structure. The approach uses text mining methods, morphological analysis, and morphological synthesis to produce poetry in Finnish. We present some promising results obtained via the combination of these methods and preliminary evaluation results of poetry generated by the system.Peer reviewe

Harnessing NLG to Create Finnish Poetry Automatically

Peer reviewe

Morphologically motivated word classes for very large vocabulary speech recognition of Finnish and Estonian

We study class-based n-gram and neural network language models for very large vocabulary speech recognition of two morphologically rich languages: Finnish and Estonian. Due to morphological processes such as derivation, inflection and compounding, the models need to be trained with vocabulary sizes of several millions of word types. Class-based language modelling is in this case a powerful approach to alleviate the data sparsity and reduce the computational load. For a very large vocabulary, bigram statistics may not be an optimal way to derive the classes. We thus study utilizing the output of a morphological analyzer to achieve efficient word classes. We show that efficient classes can be learned by refining the morphological classes to smaller equivalence classes using merging, splitting and exchange procedures with suitable constraints. This type of classification can improve the results, particularly when language model training data is not very large. We also extend the previous analyses by rescoring the hypotheses obtained from a very large vocabulary recognizer using class-based neural network language models. We show that despite the fixed vocabulary, carefully constructed classes for word-based language models can in some cases result in lower error rates than subword-based unlimited vocabulary language models.We study class-based n-gram and neural network language models for very large vocabulary speech recognition of two morphologically rich languages: Finnish and Estonian. Due to morphological processes such as derivation, inflection and compounding, the models need to be trained with vocabulary sizes of several millions of word types. Class-based language modelling is in this case a powerful approach to alleviate the data sparsity and reduce the computational load. For a very large vocabulary, bigram statistics may not be an optimal way to derive the classes. We thus study utilizing the output of a morphological analyzer to achieve efficient word classes. We show that efficient classes can be learned by refining the morphological classes to smaller equivalence classes using merging, splitting and exchange procedures with suitable constraints. This type of classification can improve the results, particularly when language model training data is not very large. We also extend the previous analyses by rescoring the hypotheses obtained from a very large vocabulary recognizer using class-based neural network language models. We show that despite the fixed vocabulary, carefully constructed classes for word-based language models can in some cases result in lower error rates than subword-based unlimited vocabulary language models.Peer reviewe

HFST—a System for Creating NLP Tools

The paper presents and evaluates various NLP tools that have been created using the open source library HFST--Helsinki Finite-State Technology and outlines the minimal extensions that this has required to a pure finite-state system. In particular, the paper describes an implementation and application of p-match presented by Karttunen at SFCM 2011.Peer reviewe

Kansalliskirjaston digitoitu historiallinen lehtiaineisto 1771–1910: sanatason laatu, kokoelmien käyttö ja laadun parantaminen

Informaatiotutkimuksen päivät 2016