The Resource Description Framework Schema (RDFS ) as RDF, a W3C Recommendation. As with XML needed in a specific application, the definition of a specific document type, for example as a document type definition (DTD), the RDF model only specifies a syntax for common data exchange. For the interpretation of formulated in RDF statements requires a common vocabulary such as Dublin Core. Such a vocabulary is called ontology, if it contains both rules for the correct use of the defined resources in it.
RDF Schema (RDFS ) is a vocabulary available, with the aid of a particular application domain can be modeled. Moreover, occurring in the domain resources, their properties and relations to each other can be represented by RDFS. One can thus formalize with RDFS simple ontologies. RDFS is based on the idea of a set-theoretic model class. It is important classes and properties that are modeled separately. The class concept makes it possible to define a formal description of the semantics of RDF elements used.
In addition, there are a number of other RDFS ontology description languages such as F -Logic, DAML OIL. The Web Ontology Language (OWL ), the official successor of DAML OIL, is to eliminate the shortcomings of RDFS. OWL is partly based on description logic and was enriched by set-theoretic constructs.
RDF Schema terms
RDF itself provides a single term for typing the type element available. In addition, however, in order for example to create a taxonomy, other terms (class, property, derivative, ... ) is required. The following terms, it is possible to define a formal vocabulary for a specific knowledge domain, ie to create a primitive ontology:
- Classes Class: The class concept. Defines an abstract object -resistant and is used in conjunction with rdf: type to generate instances.
- Resource: Each entity in an RDF model is an instance of that particular class.
- Property: The base class for properties. Is a subclass of Resource.
- Literal: class literal, ie, strings etc.
- SubClassOf: A transitive property laying down the inheritance hierarchies of classes.
- SubPropertyOf: A transitive property laying down the inheritance hierarchies of properties.
- Domain: Specifies the data type of the subject of a property in relation to a class. As in the RDFS properties are defined per se, regardless of the classes should / must be set with these properties, for which classes a property makes sense. This could be defined for example as a domain of the property hatFarbe both the Car class and the class ball.
- Range: Specifies the data type of the object of a property. This can be said for example that the hatFarbe property can have value only as colors.
Formal definition of RDF using RDF Schema
- Classes Statement: triple a statement
- Property: A property that can be used as a predicate a statement.
- Bag: unordered set of resources
- Seq: Ordered set of resources
- Old: set of alternative resources
- Subject: Indicates a statement as a resource subject to
- Predicate: Indicates a statement a property as a predicate to
- Object: Indicates a statement to an object
- Type: Identifies the class of a resource
- Value: Simple assignment of a property