This work proposes a sequential tagger for named entity recognition in morphologically rich languages. Several schemes for representing the morphological analysis of a word in the context of named entity recognition are examined. Word representations are formed by concatenating word and character embeddings with the morphological embeddings based on these schemes. The impact of these representations is measured by training and evaluating a sequential tagger composed of a conditional random field layer on top of a bidirectional long short-term memory layer. Experiments with Turkish, Czech, Hungarian, Finnish and Spanish produce the state-of-the-art results for all these languages, indicating that the representation of morphological information improves performance.

Previous studies have shown that linguistic features of a word such as possession, genitive or other grammatical cases can be employed in word representations of a named entity recognition (NER) tagger to improve the performance for morphologically rich languages. However, these taggers require external morphological disambiguation (MD) tools to function which are hard to obtain or non-existent for many languages. In this work, we propose a model which alleviates the need for such disambiguators by jointly learning NER and MD taggers in languages for which one can provide a list of candidate morphological analyses. We show that this can be done independent of the morphological annotation schemes, which differ among languages. Our experiments employing three different model architectures that join these two tasks show that joint learning improves NER performance. Furthermore, the morphological disambiguator’s performance is shown to be competitive.

In this work, we present new state-of-the-art results of 93.59,% and 79.59,% for Turkish and Czech named entity recognition based on the model of (Lample et al., 2016). We contribute by proposing several schemes for representing the morphological analysis of a word in the context of named entity recognition. We show that a concatenation of this representation with the word and character embeddings improves the performance. The effect of these representation schemes on the tagging performance is also investigated.

Distributed word representations which are learned using unsupervised methods are employed in many Natural Language Processing (NLP) tasks. They have led to state-of-the-art results in many NLP tasks for many languages. There have been studies reporting that word representations include morphological and semantical information. There are also work that aim to propose word representations which handle the morphological and syntactical information better. However, studies that evaluate the quality of the word representations for morphologically rich languages like Turkish are limited. In this study, we aim to explore the syntactic and morphological information captured by the Turkish word representations which are learned using skip-gram method on a large corpus. To assess the quality of information found in relations between Turkish word embeddings, analogical reasoning task is performed using couples consisting of root words and their inflected or derivative forms. We contribute with detailed experiments and show that word embeddings trained with skip-gram method have differing capabilities in capturing information for inflection and derivation groups in Turkish. We make the test sets and word embeddings publicly available to other researchers for further research.

In most of the natural language processing tasks, state-of-the-art systems usually rely on machine learning methods for building their mathematical models. Given that the majority of these systems employ supervised learning strategies, a corpus that is annotated for the problem area is essential. The current method for annotating a corpus is to hire several experts and make them annotate the corpus manually or by using a helper software. However, this method is costly and time-consuming. In this paper, we propose a novel method that aims to solve these problems. By employing a multiplayer collaborative game that is playable by ordinary people on the Internet, it seems possible to direct the covert labour force so that people can contribute by just playing a fun game. Through a game site which incorporates some functionality inherited from social networking sites, people are motivated to contribute to the annotation process by answering questions about the underlying morphological features of a target word. The experiments show that the 63.5% of the actual question types are successful based on a two-phase evaluation.