We extend the description logic EL++ with reflexive roles
and range restrictions, and show that subsumption remains tractable if
a certain syntactic restriction is adopted. We also show that subsumption
becomes PSpace-hard (resp. undecidable) if this restriction is weakened
(resp. dropped). Additionally, we prove that tractability is lost when
symmetric roles are added: in this case, subsumption becomes ExpTime-
hard
What is the Semantic Web? Read on for a brief introduction to the Semantic Web, how to get started using it, and to understand why we should invest in making our content semantic.
Ontotext GraphDB is a highly-efficient and robust graph database with RDF and SPARQL support. This documentation is a comprehensive guide, which explains every feature of GraphDB as well as topics such as setting up a repository, loading and working with data, tuning its performance, scaling, etc.
he W3C Web Ontology Language (OWL) is a Semantic Web language designed to represent rich and complex knowledge about things, groups of things, and relations between things.
The OWL 2 Web Ontology Language, informally OWL 2, is an ontology language for the Semantic Web with formally defined meaning. OWL 2 ontologies provide classes, properties, individuals, and data values and are stored as Semantic Web documents. OWL 2 ontologies can be used along with information written in RDF, and OWL 2 ontologies themselves are primarily exchanged as RDF documents.
OWL lets you say much more about your data model, it shows you how to work efficiently with database queries and automatic reasoners, and it provides useful annotations for bringing your data models into the real world.
The Visual Notation for OWL ontologies (VOWL - pronounced "vowel" [vou-uh l]) provides graphical representations for elements of the Web Ontology Language (OWL). It allows for an integrated view on ontologies that visualizes classes (circles) along with their individuals (sections in the circles) and property relations (connecting lines and arrows).