The main objective of explanations is to transmit knowledge to humans. This work proposes to construct informative explanations for predictions made from machine learning models. Motivated by the observations from social sciences, our approach selects data points from the training sample that exhibit special characteristics crucial for explanation, for instance, ones contrastive to the classification prediction and ones representative of the models. Subsequently, semantic concepts are derived from the selected data points through the use of domain ontologies. These concepts are filtered and ranked to produce informative explanations that improves human understanding. The main features of our approach are that (1) knowledge about explanations is captured in the form of ontological concepts, (2) explanations include contrastive evidences in addition to normal evidences, and (3) explanations are user relevant.

Recent years have witnessed the enormous success of low-dimensional vector space representations of knowledge graphs to predict missing facts or find erroneous ones. Currently, however, it is not yet well-understood how ontological knowledge, e.g. given as a set of (existential) rules, can be embedded in a principled way. To address this shortcoming, in this paper we introduce a framework based on convex regions, which can faithfully incorporate ontological knowledge into the vector space embedding. Our technical contribution is two-fold. First, we show that some of the most popular existing embedding approaches are not capable of modelling even very simple types of rules. Second, we show that our framework can represent ontologies that are expressed using so-called quasi-chained existential rules in an exact way, such that any set of facts which is induced using that vector space embedding is logically consistent and deductively closed with respect to the input ontology.

The Sensor, Observation, Sample, and Actuator (SOSA) ontology provides a formal but lightweight general-purpose specification for modeling the interaction between the entities involved in the acts of observation, actuation, and sampling. SOSA is the result of rethinking the W3C-XG Semantic Sensor Network (SSN) ontology based on changes in scope and target audience, technical developments, and lessons learned over the past years. SOSA also acts as a replacement of SSN's Stimulus Sensor Observation (SSO) core. It has been developed by the first joint working group of the Open Geospatial Consortium (OGC) and the World Wide Web Consortium (W3C) on Spatial Data on the Web. In this work, we motivate the need for SOSA, provide an overview of the main classes and properties, and briefly discuss its integration with the new release of the SSN ontology as well as various other alignments to specifications such as OGC's Observations and Measurements (O&M), Dolce-Ultralite (DUL), and other prominent ontologies. We will also touch upon common modeling problems and application areas related to publishing and searching observation, sampling, and actuation data on the Web. The SOSA ontology and standard can be accessed at https://www.w3.org/TR/vocab-ssn/. Keywords: Ontology, Sensor, Observation, Actuator, Linked Data, Web of Things, Internet of Things, Schema.org 1. Introduction and Motivation In their broadest definition sensors detect and react to changes in the environment that directly or indirectly reveal the value of a property. The process of determining this, not necessarily numeric, value is called an observation.

The Web and its Semantic extension (i.e. Linked Open Data) contain open global-scale knowledge and make it available to potentially intelligent machines that want to benefit from it. Nevertheless, most of Linked Open Data lack ontological distinctions and have sparse axiomatisation. For example, distinctions such as whether an entity is inherently a class or an individual, or whether it is a physical object or not, are hardly expressed in the data, although they have been largely studied and formalised by foundational ontologies (e.g. DOLCE, SUMO). These distinctions belong to common sense too, which is relevant for many artificial intelligence tasks such as natural language understanding, scene recognition, and the like. There is a gap between foundational ontologies, that often formalise or are inspired by pre-existing philosophical theories and are developed with a top-down approach, and Linked Open Data that mostly derive from existing databases or crowd-based effort (e.g. DBpedia, Wikidata). We investigate whether machines can learn foundational distinctions over Linked Open Data entities, and if they match common sense. We want to answer questions such as "does the DBpedia entity for dog refer to a class or to an instance?". We report on a set of experiments based on machine learning and crowdsourcing that show promising results.

When ontologies cover overlapping topics, the overlap can be represented using ontology alignments. These alignments need to be continuously adapted to changing ontologies. Especially for large ontologies this is a costly task often consisting of manual work. Finding changes that do not lead to an adaption of the alignment can potentially make this process significantly easier. This work presents an approach to finding these changes based on RDF embeddings and common classification techniques. To examine the feasibility of this approach, an evaluation on a real-world dataset is presented. In this evaluation, the best classifiers reached a precision of 0.8.

This paper reconstructs the Freebase data dumps to understand the underlying ontology behind Google's semantic search feature. The Freebase knowledge base was a major Semantic Web and linked data technology that was acquired by Google in 2010 to support the Google Knowledge Graph, the backend for Google search results that include structured answers to queries instead of a series of links to external resources. After its shutdown in 2016, Freebase is contained in a data dump of 1.9 billion Resource Description Format (RDF) triples. A recomposition of the Freebase ontology will be analyzed in relation to concepts and insights from the literature on classification by Bowker and Star. This paper will explore how the Freebase ontology is shaped by many of the forces that also shape classification systems through a deep dive into the ontology and a small correlational study. These findings will provide a glimpse into the proprietary blackbox Knowledge Graph and what is meant by Google's mission to "organize the world's information and make it universally accessible and useful".

In the classical database management systems (DBMS) setting, a query Q is evaluated against a database D. However, it has come to the attention of the database community the necessity to also include ontological reasoning and description logics (DLs) along with standard database techniques (Calvanese et al. 2007). As such, the ontological database management systems (ODBMS) has arised. In ODBMS, the classical database is enhanced with an ontology (Baader et al. 2016) in the form of logical assertions that generate new intensional knowledge. An expressive form of such logical assertions is the so-called tuplegenerating dependencies (TGDs), i.e., Horn rules extended by allowing existential quantifiers to appear in the rule heads (Cabibbo 1998; Patel-Schneider and Horrocks 2007; Calì, Gottlob, and Lukasiewicz 2009). Queries are evaluated against a database D and set of TGDs Σ (i.e., D Σ) rather than just D, as in the classical setting. Since for a given database D, a set Σ of TGDs, and a conjunctive query Q, the problem of determining if D Σ Q, i.e., the conjunctive query answering (CQ-Ans) problem, is undecidable in general (Beeri and Vardi 1981; Baget et al. 2011; Rosati 2011; Calì, Gottlob, and Pieris 2012; Calì, Gottlob, and Kifer 2013), a major research effort has been put forth to identifying syntactic conditions on TGDs for which CQ-Ans is decidable.

We introduce the Florida Annotated Corpus for Translational Science (FACTS), which currently consists of 20 case reports about hypertension that we annotated with Vital Sign Ontology (VSO) classes. We describe the annotation method, the annotation results, interannotator agreement measure, and the availability of the corpus and supporting tools for annotating corpora with OWL ontologies. We also discuss issues and limitations of VSO for annotating vital sign data in case reports.

Nowadays, it is well accepted that formal ontologies are commonly used as support for the axiomatisation of the knowledge describing a domain of interest. In particular, for domains in the engineering area where concepts are well mastered by the different stakeholders, ontologies play a major role for knowledge exchange and heterogeneity reduction. Meanwhile, we observe that defining a formal framework for integrating both ontologies represented by knowledge models and design models of particular systems did not draw the attention of many researchers in system engineering. Approaches like those of [3][4][5][7][9][12] supporting the integration of both ontologies and design models contribute to strengthen these design models by offering the capability to design models to borrow knowledge from ontologies, using a particular annotation relationship. As a consequence, the design models are enriched and strengthened with axioms, theorems or invariants issued from the used ontologies. This paper presents a summary of the work achieved in the context of the French ANR IMPEX research project. Ontologies are formalised as theories with axioms, theorems and reasoning rules. Event-B [1] has been chosen as the ground formal modelling technique for all our developments.

Microbiology research has access to a very large amount of public information on the habitats of microorganisms. Many areas of microbiology research uses this information, primarily in biodiversity studies. However the habitat information is expressed in unstructured natural language form, which hinders its exploitation at large-scale. It is very common for similar habitats to be described by different terms, which makes them hard to compare automatically, e.g. intestine and gut. The use of a common reference to standardize these habitat descriptions as claimed by (Ivana et al., 2010) is a necessity. We propose the ontology called OntoBiotope that we have been developing since 2010. The OntoBiotope ontology is in a formal machine-readable representation that enables indexing of information as well as conceptualization and reasoning.