Reasoning Web: Logical Foundation of Knowledge Graph Construction and Query Answering

Abstract

The question whether an ontology can safely be replaced by another, possibly simpler, one is fundamental for many ontology engineering and maintenance tasks. It underpins, for example, ontology versioning, ontology modularization, forgetting, and knowledge exchange. What 'safe replacement' means depends on the intended application of the ontology. If, for example, it is used to query data, then the answers to any relevant ontology-mediated query should be the same over any relevant data set; if, in contrast, the ontology is used for conceptual reasoning, then the entailed subsumptions between concept expressions should coincide. This gives rise to different notions of ontology inseparability such as query inseparability and concept inseparability, which generalize corresponding notions of conservative extensions. We survey results on various notions of inseparability in the context of description logic ontologies, discussing their applications, useful model-theoretic characterizations, algorithms for determining whether two ontologies are inseparable (and, sometimes, for computing the difference between them if they are not), and the computational complexity of this problem.ALC obtained by disallowing the constructors ⊥, ¬, ⊔ and ∀ is known as EL. Thus, EL concepts are constructed using ⊤, ⊓ and ∃ only [6]. We also consider extensions of EL with the constructors in Table 2. For example, ELI u denotes the extension of EL with inverse roles and the universal role. The fragments of ALCI and ALCHI, in which CIs are of the form

Entity Enabled Relation Linking

“…This has also impacted the performance, and we outperform the existing baseline approaches for relation linking. We hope, our work sets a foundation for the research community to exploit (approximate) ontology reasoning [13,15,[21][22][23]33] in finding correct predicates for the questions and then applying machine learning approaches on top of it for better results. Our framework is reusable, and we have integrated it to Frankenstein framework for its reusability in creating collaborative question answering systems.…”

“…More formally, we define a knowledge graph [23,24] G =T ∪ A consisting of a data sub-graph A (or ABox) and a schema sub-graph T (or TBox). Facts in the ABox are represented as triples of the following two forms:…”