ΑΝΑΠΑΡΑΣΤΑΣΗ ΓΝΩΣΗΣ ΣΤΟΝ ΠΑΓΚΟΣΜΙΟ ΙΣΤΟ OWL

RDF-RDFS Limitations Binary ground predicates Only subclass & subproperty hierarchy Domain and range definitions

RDF doesn’t support… Local scope of properties. Disjointness of classes. Boolean combinations of classes. Cardinality restrictions. Special characteristics of properties.

OWL OWL Fullfully compatible with RDF OWL DLefficient reasoning OWL Liteeasier to grasp/implement

OWL Header <rdf:RDF xmlns:owl =" xmlns:rdf =" xmlns:rdfs=" xmlns:xsd =" An example OWL ontology <owl:priorVersion rdf:resource=" <owl:imports rdf:resource=" University Ontology

Class Element Disjointness Equivalence

Predefined Classes every class is a subclass of owl:Thing every class is a superclass of owl:Nothing

Properties Object properties, relates objects to other objects Data type properties, relates objects to data type values

Inverse Properties Equivalent Properties

Property Restrictions Every person that teaches a first Year Course is a professor (universal restriction) First-year courses are taught by professors only Mathematics Courses are taught only by professor #949318

Property Restrictions For every academic Staff member there exists an undergraduate course that is taught by him (existential restriction) All academic staff members must teach at least one undergraduate course

Cardinality Restriction 1 A course is taught by at least one Person

Cardinality Restriction A department must have at least 10 members but no more than 30.

Special Properties owl:TransitiveProperty “is taller than”, or “is ancestor of” owl:SymmetricProperty “is sibling of”. owl:FunctionalProperty a property that has at most one value for each object owl:InverseFunctionalProperty a property for which two different objects cannot have the same value

Special Properties

Boolean Combinations

Boolean Combinations

Boolean Combinations administrative staff are those staff members that are neither faculty nor technical support staff

Enumerations

Instances (RDF) or We can also provide further details, such as: 39

Instances (RDF) Just because two instances have a different name or ID does not imply that they are different individuals. To ensure that different individuals are indeed recognized as such, we must explicitly assert their inequality: to state the inequality of a large number of individuals:

Layering of OWL OWL Full OWL DL – Vocabulary partitioning. – Explicit typing. – Property separation. – No transitive cardinality restrictions. – Restricted anonymous classes. OWL Lite – The constructors owl:oneOf, owl:disjointWith, owl:unionOf, owl:complementOf, and owl:hasValue are not allowed. – Cardinality statements can only be made on the values 0 or 1 and no longer on arbitrary non- negative integers. – owl:equivalentClass statements can no longer be made between anonymous classes but only between class identifiers.

open-world assumption –we may not deduce falsity from the absence of truth non-unique-name assumption –Just because two instances have a different name or ID does not imply that they are different individuals

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