Primer Glossary

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| Datalog | A query and rule language for deductive databases that syntactically is a subset of Prolog. |
| D-entailment | A vocabulary entailment of an RDF graph that respects the 'meaning' of data types. |
| Description Logics | A family of formal knowledge representation languages that are subsets of first order logic, but have more efficient decision problems. |
| Horn Logic | Broadly means a system of logic whose semantics can be captured by Horn clauses. A Horn clause has at most one positive literal and allows for an IF...THEN interpretation, hence the common term 'Horn Rule'. |
| Knowledge Base | (In the Semantic Web sense) is a database of both assertions (ground statements) and an inference system for deducing further knowledge based on the structure of the data and a formal vocabulary. |
| Knowledge Representation | An area in artificial intelligence that concerns representing knowledge in a formal way such that it permits automated processing (reasoning). |
| Materialisation | The process of inferring and storing (for later retrieval or use in query answering) every piece of information that can be deduced from a knowledge base's asserted facts and vocabulary. |
| Named Graph | A group of statements identified by a URI. It allows a subset of statements in a repository to be manipulated or processed separately. |
| Ontology | A shared conceptualisation of a domain, described using a formal (knowledge) representation language. |
| OWL | See 'Web Ontology Language' |
| OWL Horst | An entailment system built upon RDF Schema, see R-entailment. |
| Predicate Logic | Generic term for symbolic formal systems like first-order logic, second-order logic, etc. Its formulas may contain variables which can be quantified. |
| RDF Graph Model | The interpretation of a collection of RDF triples as a graph, where resources are nodes in the graph and predicates form the arcs betweens nodes. Therefore one statement leads to one arc between two nodes (subject and object). |
| RDF Schema | A vocabulary description language for RDF with formal semantics. |
| Resource | An element of the RDF model that represents a thing that can be described, i.e. a unique name to identify an object or concept. |
| R-entailment | A more general semantics layered on RDFS where any set of rules (i.e. rules that extend or even modify RDFS) are permitted. Rules are of the form IF...THEN... and use RDF statement patterns in their premises and consequences, with variables allowed in any position. |

| Triple | A basic unit of information expression in RDF. A triple consists of a subject-predicate-object. |
| Universal Resource Identifier (URI) | Is a string of characters used to (uniquely) identify a resource. |
| Web Ontology Language (OWL) | A family of W3C knowledge representation languages that can be used to create ontologies. |
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