Constantine Lignos


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If You Build Your Own NER Scorer, Non-replicable Results Will Come
Constantine Lignos | Marjan Kamyab
Proceedings of the First Workshop on Insights from Negative Results in NLP

We attempt to replicate a named entity recognition (NER) model implemented in a popular toolkit and discover that a critical barrier to doing so is the inconsistent evaluation of improper label sequences. We define these sequences and examine how two scorers differ in their handling of them, finding that one approach produces F1 scores approximately 0.5 points higher on the CoNLL 2003 English development and test sets. We propose best practices to increase the replicability of NER evaluations by increasing transparency regarding the handling of improper label sequences.


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The Challenges of Optimizing Machine Translation for Low Resource Cross-Language Information Retrieval
Constantine Lignos | Daniel Cohen | Yen-Chieh Lien | Pratik Mehta | W. Bruce Croft | Scott Miller
Proceedings of the 2019 Conference on Empirical Methods in Natural Language Processing and the 9th International Joint Conference on Natural Language Processing (EMNLP-IJCNLP)

When performing cross-language information retrieval (CLIR) for lower-resourced languages, a common approach is to retrieve over the output of machine translation (MT). However, there is no established guidance on how to optimize the resulting MT-IR system. In this paper, we examine the relationship between the performance of MT systems and both neural and term frequency-based IR models to identify how CLIR performance can be best predicted from MT quality. We explore performance at varying amounts of MT training data, byte pair encoding (BPE) merge operations, and across two IR collections and retrieval models. We find that the choice of IR collection can substantially affect the predictive power of MT tuning decisions and evaluation, potentially introducing dissociations between MT-only and overall CLIR performance.

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SARAL: A Low-Resource Cross-Lingual Domain-Focused Information Retrieval System for Effective Rapid Document Triage
Elizabeth Boschee | Joel Barry | Jayadev Billa | Marjorie Freedman | Thamme Gowda | Constantine Lignos | Chester Palen-Michel | Michael Pust | Banriskhem Kayang Khonglah | Srikanth Madikeri | Jonathan May | Scott Miller
Proceedings of the 57th Annual Meeting of the Association for Computational Linguistics: System Demonstrations

With the increasing democratization of electronic media, vast information resources are available in less-frequently-taught languages such as Swahili or Somali. That information, which may be crucially important and not available elsewhere, can be difficult for monolingual English speakers to effectively access. In this paper we present an end-to-end cross-lingual information retrieval (CLIR) and summarization system for low-resource languages that 1) enables English speakers to search foreign language repositories of text and audio using English queries, 2) summarizes the retrieved documents in English with respect to a particular information need, and 3) provides complete transcriptions and translations as needed. The SARAL system achieved the top end-to-end performance in the most recent IARPA MATERIAL CLIR+summarization evaluations. Our demonstration system provides end-to-end open query retrieval and summarization capability, and presents the original source text or audio, speech transcription, and machine translation, for two low resource languages.


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Modeling Infant Word Segmentation
Constantine Lignos
Proceedings of the Fifteenth Conference on Computational Natural Language Learning


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Recession Segmentation: Simpler Online Word Segmentation Using Limited Resources
Constantine Lignos | Charles Yang
Proceedings of the Fourteenth Conference on Computational Natural Language Learning