(4th-Julu-2020)
• RDF (the Resource Description Framework) is a language built on XML, providing individual-property-value triples.
• RDF-S (RDF Schema) lets you define resources (and so also properties) in terms of other resources (e.g., using subClassOf). RDF-S also lets you restrict the domain and range of properties and provides containers (sets, sequences, and alternatives - one of which must be true).
• OWL (the Web Ontology Language) is an ontology language for the World Wide Web. It defines some classes and properties with a fixed interpretation that can be used for describing classes, properties, and individuals. It has built-in mechanisms for equality of individuals, classes, and properties, in addition to restricting domains and ranges of properties and other restrictions on properties (e.g., transitivity, cardinality). There have been some efforts to build large universal ontologies, such as cyc (www.cyc.com), but the idea of the semantic web is to allow communities to converge on ontologies.
• A conceptualization is a mapping between symbols used in the computer (i.e., the vocabulary) and the individuals and relations in the world. It provides a particular abstraction of the world and notation for that abstraction. A conceptualization for small knowledge bases can be in the head of the designer or specified in natural language in the documentation. This informal specification of a conceptualization does not scale to larger systems where the conceptualization must be shared.
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