Lukas Paul Achatius Galke

Neural networks, genetic algorithms, natural language, and other bio-inspired stuff

Christian-Albrechts-Unversität zu Kiel

ZBW - Leibniz Information Centre for Economics

Publications

A Case Study of Closed-Domain Response Suggestion with Limited Training Data
Lukas GalkeGunnar GerstenkornAnsgar Scherp

We analyze the problem of response suggestion in a closed domain along a real-world scenario of a digital library. We present a text-processing pipeline to generate question-answer pairs from chat transcripts. On this limited amount of training data, we compare retrieval-based, conditioned-generation, and dedicated representation learning approaches for response suggestion. Our results show that retrieval-based methods that strive to find similar, known contexts are preferable over parametric approaches from the conditioned-generation family, when the training data is limited. We, however, identify a specific representation learning approach that is competitive to the retrieval-based approaches despite the training data limitation.

Multi-Modal Adversarial Autoencoders for Recommendations of Citations and Subject Labels
Lukas GalkeFlorian MaiIacopo VaglianoAnsgar Scherp

We present multi-modal adversarial autoencoders for recommendation and evaluate them on two different tasks: citation recommendation and subject label recommendation. We analyze the effects of adversarial regularization, sparsity, and different input modalities. By conducting 408 experiments, we show that adversarial regularization consistently improves the performance of autoencoders for recommendation. We demonstrate, however, that the two tasks differ in the semantics of item co-occurrence in the sense that item co-occurrence resembles relatedness in case of citations, yet implies diversity in case of subject labels. Our results reveal that supplying the partial item set as input is only helpful, when item co-occurrence resembles relatedness. When facing a new recommendation task it is therefore crucial to consider the semantics of item co-occurrence for the choice of an appropriate model.

Using Deep Learning for Title-Based Semantic Subject Indexing To Reach Competitive Performance to Full-Text
Florian MaiLukas Galke Ansgar Scherp

For (semi-)automated subject indexing systems in digital libraries, it is often more practical to use metadata such as the title of a publication instead of the full-text or the abstract. Therefore, it is desirable to have good text mining and text classification algorithms that operate well already on the title of a publication. So far, the classification performance on titles is not competitive with the performance on the full-texts if the same number of training samples is used for training. However, it is much easier to obtain title data in large quantities and to use it for training than full-text data. In this paper, we investigate the question how models obtained from training on increasing amounts of title training data compare to models from training on a constant number of full-texts. We evaluate this question on a large-scale dataset from the medical domain (PubMed) and from economics (EconBiz). In these datasets, the titles and annotations of millions of publications are available, and they outnumber the available full-texts by a factor of 20 and 15, respectively. To exploit these large amounts of data to their full potential, we develop three strong deep learning classifiers and evaluate their performance on the two datasets. The results are promising. On the EconBiz dataset, all three classifiers outperform their full-text counterparts by a large margin. The best title-based classifier outperforms the best full-text method by 9.9%. On the PubMed dataset, the best title-based method almost reaches the performance of the best full-text classifier, with a difference of only 2.9%.

Linked Open Citation Database: How much would it cost if Libraries Cataloged and Curated the Citation Graph?
Anne Lauscher Kai Eckert Lukas Galke Ansgar Scherp Syed Tahseen Raza Rizvi Sheraz Ahmed Andreas Dengel Philipp Zumstein Annette Klein

Citations play a crucial role in the scientific discourse, in information retrieval, and in bibliometrics. Many initiatives are currently promoting the idea of having free and open citation data. Creation of citation data, however, is not part of the cataloging workflow in libraries nowadays. In this paper, we present our project Linked Open Citation Database, in which we design distributed processes and a system infrastructure based on linked data technology. The goal is to show that efficiently cataloging citations in libraries using a semi-automatic approach is possible. We specifically describe the current state of the workflow and its implementation. We show that we could significantly improve the automatic reference extraction that is crucial for the subsequent data curation. We further give insights on the curation and linking process and provide evaluation results that not only direct the further development of the project, but also allow us to discuss its overall feasibility.

Using Titles vs. Full-text as Source for Automated Semantic Document Annotation
Lukas Galke Florian Mai Alan Schelten Dennis Brunsch Ansgar Scherp

We conduct the first systematic comparison of automated semantic annotation based on either the full-text or only on the title metadata of documents. Apart from the prominent text classification baselines kNN and SVM, we also compare recent techniques of Learning to Rank and neural networks and revisit the traditional methods logistic regression, Rocchio, and Naive Bayes. Across three of our four datasets, the performance of the classifications using only titles reaches over 90% of the quality compared to the performance when using the full-text.

Word Embeddings for Practical Information Retrieval
Lukas Galke Ahmed Saleh Ansgar Scherp

We assess the suitability of word embeddings for practical information retrieval scenarios. Thus, we assume that users issue ad-hoc short queries where we return the first twenty retrieved documents after applying a boolean matching operation between the query and the documents. We compare the performance of several techniques that leverage word embeddings in the retrieval models to compute the similarity between the query and the documents, namely word centroid similarity, paragraph vectors, Word Mover’s distance, as well as our novel inverse document frequency (IDF) re-weighted word centroid similarity. We evaluate the performance using the ranking metrics mean average precision, mean reciprocal rank, and normalized discounted cumulative gain. Additionally, we inspect the retrieval models’ sensitivity to document length by using either only the title or the full-text of the documents for the retrieval task. We conclude that word centroid similarity is the best competitor to state-of-the-art retrieval models. It can be further improved by re-weighting the word frequencies with IDF before aggregating the respective word vectors of the embedding. The proposed cosine similarity of IDF re-weighted word vectors is competitive to the TF-IDF baseline and even outperforms it in case of the news domain with a relative percentage of 15%.

Theses

Embedded Retrieval
Word Embeddings for Practical Information Retrieval
Lukas Galke

We assess the suitability of word embeddings for practical information retrieval. While limiting ourselves to unsupervised models, we compare the performance of several techniques that leverage word embeddings to retrieval models (i. e., provide a query-document similarity): the intuitive word centroid similarity, dedicated paragraph vectors, the physically inspired Word Mover’s distance, as well as a novel IDF re-weighted word centroid similarity. In our comparison, we strive to simulate a strictly practical setting: short queries, a boolean matching operation, only the first twenty retrieved documents are considered. We evaluate the performance using the ranking metrics mean average precision, mean reciprocal rank and normalised discounted cumulative gain. Additionally, we inspect the retrieval models’ sensitivity to document length by using either only the title or the full-text as documents. We conclude that word centroid similarity is the best competitor to state-of-the-art retrieval models and can be further improved by re-weighting the word frequencies according to inverse document frequency before aggregating the respective word vectors of the embedding. The proposed cosine similarity of IDF re-weighted word vectors is competitive to the TF-IDF baseline and even outperforms it in case of the news domain with a relative percentage of 15%. In the context of this research contribution, a dedicated information retrieval framework has been developed. The key features include the incorporation of embedding-based retrieval models, the simulation of a practical setting, automatic evaluation as well as convenient extendability by new retrieval models. The corresponding user’s guide and developer’s guide are part of this work.

Projects

LOC-DB - Linked Open Citation Database

The LOC-DB project will develop ready-to-use tools and processes based on the linked-data technology that make it possible for a single library to meaningfully contribute to an open, distributed infrastructure for the cataloguing of citations. The project aims to prove that, by widely automating cataloguing processes, it is possible to add a substantial benefit to academic search tools by regularly capturing citation relations. These data will be made available in the semantic web to make future reuse possible. Moreover, we document effort, number and quality of the data in a well-founded cost-benefit analysis. The project will use well-known methods of information extraction and adapt them to work for arbitrary layouts of reference lists in electronic and print media. The obtained raw data will be aligned and linked with existing metadata sources. Moreover, it will be shown how these data can be integrated in library catalogues. The system will be deployable to use productively by a single library, but in principle it will also be scalable for using it in a network.

Project Overview, locdb.bib.uni-mannheim.de
MOVING - Training Towards a Society of Data-savvy Information Professionals to Enable Open Leadership Innovation

MOVING will build an innovative training platform that will enable users from all societal sectors (companies, universities, public administration) to fundamentally improve their information literacy by training how to choose, use and evaluate data mining methods in connection with their daily research tasks and to become data-savvy information professionals.

The MOVING vision, moving-project.eu