Lenz Furrer


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COVID-19 Twitter Monitor: Aggregating and Visualizing COVID-19 Related Trends in Social Media
Joseph Cornelius | Tilia Ellendorff | Lenz Furrer | Fabio Rinaldi
Proceedings of the Fifth Social Media Mining for Health Applications Workshop & Shared Task

Social media platforms offer extensive information about the development of the COVID-19 pandemic and the current state of public health. In recent years, the Natural Language Processing community has developed a variety of methods to extract health-related information from posts on social media platforms. In order for these techniques to be used by a broad public, they must be aggregated and presented in a user-friendly way. We have aggregated ten methods to analyze tweets related to the COVID-19 pandemic, and present interactive visualizations of the results on our online platform, the COVID-19 Twitter Monitor. In the current version of our platform, we offer distinct methods for the inspection of the dataset, at different levels: corpus-wide, single post, and spans within each post. Besides, we allow the combination of different methods to enable a more selective acquisition of knowledge. Through the visual and interactive combination of various methods, interconnections in the different outputs can be revealed.

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Annotating the Pandemic: Named Entity Recognition and Normalisation in COVID-19 Literature
Nico Colic | Lenz Furrer | Fabio Rinaldi
Proceedings of the 1st Workshop on NLP for COVID-19 (Part 2) at EMNLP 2020

The COVID-19 pandemic has been accompanied by such an explosive increase in media coverage and scientific publications that researchers find it difficult to keep up. We are presenting a publicly available pipeline to perform named entity recognition and normalisation in parallel to help find relevant publications and to aid in downstream NLP tasks such as text summarisation. In our approach, we are using a dictionary-based system for its high recall in conjunction with two models based on BioBERT for their accuracy. Their outputs are combined according to different strategies depending on the entity type. In addition, we are using a manually crafted dictionary to increase performance for new concepts related to COVID-19. We have previously evaluated our work on the CRAFT corpus, and make the output of our pipeline available on two visualisation platforms.


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Approaching SMM4H with Merged Models and Multi-task Learning
Tilia Ellendorff | Lenz Furrer | Nicola Colic | Noëmi Aepli | Fabio Rinaldi
Proceedings of the Fourth Social Media Mining for Health Applications (#SMM4H) Workshop & Shared Task

We describe our submissions to the 4th edition of the Social Media Mining for Health Applications (SMM4H) shared task. Our team (UZH) participated in two sub-tasks: Automatic classifications of adverse effects mentions in tweets (Task 1) and Generalizable identification of personal health experience mentions (Task 4). For our submissions, we exploited ensembles based on a pre-trained language representation with a neural transformer architecture (BERT) (Tasks 1 and 4) and a CNN-BiLSTM(-CRF) network within a multi-task learning scenario (Task 1). These systems are placed on top of a carefully crafted pipeline of domain-specific preprocessing steps.

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UZH@CRAFT-ST: a Sequence-labeling Approach to Concept Recognition
Lenz Furrer | Joseph Cornelius | Fabio Rinaldi
Proceedings of the 5th Workshop on BioNLP Open Shared Tasks

As our submission to the CRAFT shared task 2019, we present two neural approaches to concept recognition. We propose two different systems for joint named entity recognition (NER) and normalization (NEN), both of which model the task as a sequence labeling problem. Our first system is a BiLSTM network with two separate outputs for NER and NEN trained from scratch, whereas the second system is an instance of BioBERT fine-tuned on the concept-recognition task. We exploit two strategies for extending concept coverage, ontology pretraining and backoff with a dictionary lookup. Our results show that the backoff strategy effectively tackles the problem of unseen concepts, addressing a major limitation of the chosen design. In the cross-system comparison, BioBERT proves to be a strong basis for creating a concept-recognition system, although some entity types are predicted more accurately by the BiLSTM-based system.


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Crowdsourcing an OCR Gold Standard for a German and French Heritage Corpus
Simon Clematide | Lenz Furrer | Martin Volk
Proceedings of the Tenth International Conference on Language Resources and Evaluation (LREC'16)

Crowdsourcing approaches for post-correction of OCR output (Optical Character Recognition) have been successfully applied to several historic text collections. We report on our crowd-correction platform Kokos, which we built to improve the OCR quality of the digitized yearbooks of the Swiss Alpine Club (SAC) from the 19th century. This multilingual heritage corpus consists of Alpine texts mainly written in German and French, all typeset in Antiqua font. Finding and engaging volunteers for correcting large amounts of pages into high quality text requires a carefully designed user interface, an easy-to-use workflow, and continuous efforts for keeping the participants motivated. More than 180,000 characters on about 21,000 pages were corrected by volunteers in about 7 month, achieving an OCR gold standard with a systematically evaluated accuracy of 99.7% on the word level. The crowdsourced OCR gold standard and the corresponding original OCR recognition results from Abby FineReader 7 for each page are available as a resource. Additionally, the scanned images (300dpi) of all pages are included in order to facilitate tests with other OCR software.


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GU-MLT-LT: Sentiment Analysis of Short Messages using Linguistic Features and Stochastic Gradient Descent
Tobias Günther | Lenz Furrer
Second Joint Conference on Lexical and Computational Semantics (*SEM), Volume 2: Proceedings of the Seventh International Workshop on Semantic Evaluation (SemEval 2013)


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Reducing OCR Errors in Gothic-Script Documents
Lenz Furrer | Martin Volk
Proceedings of the Workshop on Language Technologies for Digital Humanities and Cultural Heritage


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Challenges in Building a Multilingual Alpine Heritage Corpus
Martin Volk | Noah Bubenhofer | Adrian Althaus | Maya Bangerter | Lenz Furrer | Beni Ruef
Proceedings of the Seventh International Conference on Language Resources and Evaluation (LREC'10)

This paper describes our efforts to build a multilingual heritage corpus of alpine texts. Currently we digitize the yearbooks of the Swiss Alpine Club which contain articles in French, German, Italian and Romansch. Articles comprise mountaineering reports from all corners of the earth, but also scientific topics such as topography, geology or glacierology as well as occasional poetry and lyrics. We have already scanned close to 70,000 pages which has resulted in a corpus of 25 million words, 10% of which is a parallel French-German corpus. We have solved a number of challenges in automatic language identification and text structure recognition. Our next goal is to identify the great variety of toponyms (e.g. names of mountains and valleys, glaciers and rivers, trails and cabins) in this corpus, and we sketch how a large gazetteer of Swiss topographical names can be exploited for this purpose. Despite the size of the resource, exact matching leads to a low recall because of spelling variations, language mixtures and partial repetitions.