Machine Learning is the study of methods for programming computers to learn. Computers are applied to a wide range of tasks, and for most of these it is relatively easy for programmers to design and implement the necessary software. However, there are many tasks for which this is difficult or impossible. These can be divided into four general categories. First, there are problems for which there exist no human experts. For example, in modern automated manufacturing facilities, there is a need to predict machine failures before they occur by analyzing sensor readings. Because the machines are new, there are no human experts who can be interviewed by a programmer to provide the knowledge necessary to build a computer system. A machine learning system can study recorded data and subsequent machine failures and learn prediction rules. Second, there are problems where human experts exist, but where they are unable to explain their expertise. This is the case in many perceptual tasks, such as speech recognition, hand-writing recognition, and natural language understanding. Virtually all humans exhibit expert-level abilities on these tasks, but none of them can describe the detailed steps that they follow as they perform them. Fortunately, humans can provide machines with examples of the inputs and correct outputs for these tasks, so machine learning algorithms can learn to map the inputs to the outputs. Third, there are problems where phenomena are changing rapidly. In finance, for example, people would like to predict the future behavior of the stock market, of consumer purchases, or of exchange rates. These behaviors change frequently, so that even if a programmer could construct a good predictive computer program, it would need to be rewritten frequently. A learning program can relieve the programmer of this burden by constantly modifying and tuning a set of learned prediction rules. Fourth, there are applications that need to be customized for each computer user separately. Consider, for example, a program to filter unwanted electronic mail messages. Different users will need different filters. It is unreasonable to expect each user to program his or her own rules, and it is infeasible to provide every user with a software engineer to keep the rules up-to-date. A machine learning system can learn which mail messages the user rejects and maintain the filtering rules automatically. Machine learning addresses many of the same research questions as the fields of statistics, data mining, and psychology, but with differences of emphasis. Statistics focuses on understanding the phenomena that have generated the data, often with the goal of testing different hypotheses about those phenomena. Data mining seeks to find patterns in the data that are understandable by people. Psychological studies of human learning aspire to understand the mechanisms underlying the various learning behaviors exhibited by people (concept learning, skill acquisition, strategy change, etc.).

Machine learning

Data Mining Practical Machine Learning Tools and Techniques

How to Do Things With Words

Knowledge graphs enable a wide variety of applications, including question answering and information retrieval. Despite the great effort invested in their creation and maintenance, even the largest (e.g., Yago, DBPedia or Wikidata) remain incomplete. We introduce Relational Graph Convolutional Networks (R-GCNs) and apply them to two standard knowledge base completion tasks: Link prediction (recovery of missing facts, i.e. subject-predicate-object triples) and entity classification (recovery of missing entity attributes). R-GCNs are related to a recent class of neural networks operating on graphs, and are developed specifically to handle the highly multi-relational data characteristic of realistic knowledge bases. We demonstrate the effectiveness of R-GCNs as a stand-alone model for entity classification. We further show that factorization models for link prediction such as DistMult can be significantly improved through the use of an R-GCN encoder model to accumulate evidence over multiple inference steps in the graph, demonstrating a large improvement of 29.8% on FB15k-237 over a decoder-only baseline.

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Modeling Relational Data with Graph Convolutional Networks

Ontologies tend to be found everywhere. They are viewed as the silver bullet for many applications, such as database integration, peer-to-peer systems, e-commerce, semantic web services, or social networks. However, in open or evolving systems, such as the semantic web, different parties would, in general, adopt different ontologies. Thus, merely using ontologies, like using XML, does not reduce heterogeneity: it just raises heterogeneity problems to a higher level. Euzenat and Shvaikos book is devoted to ontology matching as a solution to the semantic heterogeneity problem faced by computer systems. Ontology matching aims at finding correspondences between semantically related entities of different ontologies. These correspondences may stand for equivalence as well as other relations, such as consequence, subsumption, or disjointness, between ontology entities. Many different matching solutions have been proposed so far from various viewpoints, e.g., databases, information systems, and artificial intelligence. The second edition of Ontology Matching has been thoroughly revised and updated to reflect the most recent advances in this quickly developing area, which resulted in more than 150 pages of new content. In particular, the book includes a new chapter dedicated to the methodology for performing ontology matching. It also covers emerging topics, such as data interlinking, ontology partitioning and pruning, context-based matching, matcher tuning, alignment debugging, and user involvement in matching, to mention a few. More than 100 state-of-the-art matching systems and frameworks were reviewed. With Ontology Matching, researchers and practitioners will find a reference book that presents currently available work in a uniform framework. In particular, the work and the techniques presented in this book can be equally applied to database schema matching, catalog integration, XML schema matching and other related problems. The objectives of the book include presenting (i) the state of the art and (ii) the latest research results in ontology matching by providing a systematic and detailed account of matching techniques and matching systems from theoretical, practical and application perspectives.

Ontology Matching

The original Semantic Web vision foresees to describe entities in a way that the meaning can be interpreted both by machines and humans. Following that idea, large-scale knowledge graphs capturing a significant portion of knowledge have been developed. In the recent past, vector space embeddings of semantic web knowledge graphs – i.e., projections of a knowledge graph into a lower-dimensional, numerical feature space (a.k.a. latent feature space) – have been shown to yield superior performance in many tasks, including relation prediction, recommender systems, or the enrichment of predictive data mining tasks. At the same time, those projections describe an entity as a numerical vector, without any semantics attached to the dimensions. Thus, embeddings are as far from the original Semantic Web vision as can be. As a consequence, the results achieved with embeddings – as impressive as they are in terms of quantitative performance – are most often not interpretable, and it is hard to obtain a justification for a prediction, e.g., an explanation why an item has been suggested by a recommender system. In this paper, we make a claim for semantic embeddings and discuss possible ideas towards their construction.

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Make Embeddings Semantic Again

DBpedia releases consist of more than 70 multilingual datasets that cover data extracted from different language-specific Wikipedia instances. The data extracted from those Wikipedia instances are transformed into RDF using mappings created by the DBpedia community. Nevertheless, not all the mappings are correct and consistent across all the distinct language-specific DBpedia datasets. As these incorrect mappings are spread in a large number of mappings, it is not feasible to inspect all such mappings manually to ensure their correctness. Thus, the goal of this work is to propose a data-driven method to detect incorrect mappings automatically by analyzing the information from both instance data as well as ontological axioms. We propose a machine learning based approach to building a predictive model which can detect incorrect mappings. We have evaluated different supervised classification algorithms for this task and our best model achieves 93% accuracy. These results help us to detect incorrect mappings and achieve a high-quality DBpedia.

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Predicting incorrect mappings: a data-driven approach applied to DBpedia

The datasets that are part of the Linking Open Data cloud
diagramm (LOD cloud) are classified into the following topical
categories: media, government, publications, life sciences,
geographic, social networking, user-generated content,
and cross-domain. The topical categories were manually
assigned to the datasets. In this paper, we investigate to
which extent the topical classification of new LOD datasets
can be automated using machine learning techniques and the
existing annotations as supervision. We conducted experiments
with different classification techniques and different
feature sets. The best classification technique/feature set
combination reaches an accuracy of 81.62% on the task of
assigning one out of the eight classes to a given LOD dataset.
A deeper inspection of the classification errors reveals problems
with the manual classification of datasets in the current
LOD cloud.

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Towards Automatic Topical Classification of LOD Datasets

Application integration can be carried out on three different levels: the data source level, the business logic level, and the user interface level. With ontologies-based integration on the data source level dating back to the 1990s and semantic web services for integrating on the business logic level coming of age, it is time for the next logical step: employing ontologies for integration on the user interface level. Such an approach supports both the developer (in terms of reduced development times) and the user (in terms of better usability) of integrated applications. In this paper, we introduce a framework employing ontologies for integrating applications on the user interface level.

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Ontologies for User Interface Integration

Wikipedia is often used a source of surface forms, or alternative reference strings for an entity, required for entity linking, disambiguation or coreference resolution tasks. Surface forms have been extracted in a number of works from Wikipedia labels, redirects, disambiguations and anchor texts of internal Wikipedia links, which we complement with anchor texts of external Wikipedia links from the Common Crawl web corpus. We tackle the problem of quality of Wikipedia-based surface forms, which has not been raised before. We create the gold standard for the dataset quality evaluation, which reveales the surprisingly low precision of the Wikipedia-based surface forms. We propose filtering approaches that allowed boosting the precision from 75% to 85% for a random entity subset, and from 45% to more than 65% for the subset of popular entities. The filtered surface form dataset as well the gold standard are made publicly available.

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Heiko Paulheim

Papers

Make Embeddings Semantic Again

Predicting incorrect mappings: a data-driven approach applied to DBpedia

Towards Automatic Topical Classification of LOD Datasets

Ontologies for User Interface Integration

Gathering Alternative Surface Forms for DBpedia Entities.