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RDF and OWL
The document provides an overview of RDF (Resource Description Framework) and OWL (Web Ontology Language) as foundational components of the Semantic Web. It explains the structure of RDF using triples to describe resources, properties, and classes, and highlights the enhanced capabilities offered by OWL for defining relationships and properties, including disjoint classes and transitive relationships. The document also touches on RDF namespaces, OWL's subclassing, and the use of SKOS for hierarchical information organization.
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Introduction to RDF and OWL presented by Rachel Lovinger in 2007.
RDF defines a framework for describing resources with a structured format.
Resources are uniquely identified using URIs to make meaningful RDF statements.
RDF consists of resources, properties, and classes, forming statements as triples.
Triples represent information and properties in RDF can define relationships.
Types of properties in RDF include type, subClassOf, subPropertyOf, range, and domain.
Labels and comments in RDF provide human-readable context for resources.
RDF allows flexible exploration of data relationships and efficient large-scale data handling.
Namespaces are used in XML for qualifying names to indicate standards or versions.
OWL aims to develop web-compatible ontologies and extend RDF functionalities.
OWL allows classification of concepts, relationships, and richer vocabulary than RDF.
OWL defines class relationships such as disjoint, complement, and equivalency.
Enhanced relationships in OWL include symmetry, transitivity, and inverses.
OWL defines members of classes based on property restrictions for better organization.
OWL allows expressing first-order logic to deduce relationships based on facts.
OWL can create new triples and deduce new facts based on existing information.
Three flavors of OWL: Lite, DL, and Full, each with different capability restrictions.
SKOS is based on RDF for expressing hierarchical information and can extend to OWL.
Links to further resources on RDF, OWL, SKOS, and related topics.
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RDF and OWL
- 1. RDF & OWLA simple overview of the b uilding blocks of the Semantic Web Presented by Rachel Lovinger Semantic Web Affinity Group December 2007
- 2. RDF = Resource Description Framework
- 3. Purpose: To providea structure (aka framework) for describing identified things (aka resources) RDF
- 4. Identified ? In order to make meaningful statements in RDF, the thing you’re talking about has to be identified in some unique way. http://www.foaf.com/Person#RachelLovinger http://www.allmovie.com/Actor#WillSmith URIs (uniform resource identifiers) look like URLs, but they may not represent an actual web page. RDF
- 5. Composed of threebasic elements Resources – the things being described Properties – the relationships between things Classes – the buckets used to group the things RDF
- 6. The elements arecombined to make simple statements in the form of Triples <Subject> <Predicate> <Object> Men In Black stars Will Smith <MenInBlack> <hasStar> <WillSmith> RDF
- 7. Information Expressed inTriples <http://www.w3.org/2001/sw/RDFCore/ntriples/> <dc:creator> "Dave Beckett" . <http://www.w3.org/2001/sw/RDFCore/ntriples/> <dc:creator> "Art Barstow" . <http://www.w3.org/2001/sw/RDFCore/ntriples/> <dc:publisher> <http://www.w3.org/> . Can also be expressed as XML <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:dc="http://purl.org/dc/elements/1.1/"> <rdf:Description rdf:about="http://www.w3.org/2001/sw/RDFCore/ntriples/"> <dc:creator>Art Barstow</dc:creator> <dc:creator>Dave Beckett</dc:creator> <dc:publisher rdf:resource="http://www.w3.org/"/> </rdf:Description> </rdf:RDF> RDF
- 8. RDF Properties type subClassOf subPropertyOf range domain label comment RDF
- 9. type –a resource belongs to a certain class <WillSmith> <type> <Actor> This defines which properties will be relevant to Will Smith. RDF
- 10. subClassOf –a class belongs to a parent class <Actor> <subClassOf> <Person> This means that all members of the actor class are also members of the Person class. All properties are inherited, and new properties specific to Actor can be added. <WillSmith> <type> <Actor> implies <WillSmith> <type> <Person> RDF
- 11. subPropertyOf –a property has a parent property <hasStar> <subPropertyOf> <hasActor> This means that, if you make a statement using the hasStar property, a more general statement using the hasActor property is also true. <MenInBlack> <hasStar> <WillSmith> implies <MenInBlack> <hasActor> <WillSmith> RDF
- 12. range & domain – the types of resources that use a property <hasStar> <range> <Actor> <hasStar> <domain> <Movie> This means that, if you make a statement using the hasStar property, the system will assume that the subject is a Movie and the object is an Actor. <WillSmith> <hasStar> <MenInBlack> is an untrue statement, but not invalid RDF
- 13. label –a human-readable name for a resource <http://www.allmovie.com/Actor#WillSmith> <label> <Will Smith> RDF
- 14. comment –a human-readable description <https://aarfwiki.main.corp/wiki/index.php/File:RDF_OWL.pdf> <comment> <A presentation that Rachel gave at the December 2007 Semantic Web Affinity Group Meeting> RDF
- 15. RDF Blackberry FruittypeOf BerryPie EdibleThing typeOf subClassOf ingredientOf Blackberry
- 16. Why is RDFuniquely suited to expressing data and data relationships? More flexible – data relationships can be explored from all angles More efficient – large scale, data can be read more quickly not linear like a traditional database not hierarchical like XML RDF
- 17.
- 18. A method forqualifying names used in an XML document. Can be used to indicate usage of a standard, or to specify a unique version of the term. dc:creator rdf:type foaf:Person foaf:knows aarf:Employee Namespaces
- 19. OWL = Web Ontology Language
- 20.
- 21. Purpose: To developontologies that are compatible with the World Wide Web. OWL
- 22. Ontologies ? Definition and classification of concepts and entities, and the relationships between them. OWL
- 23. Based on thebasic elements of RDF; adds more vocabulary for describing properties and classes. Relationships between classes (ex: disjointWith) Equality (ex: sameAs) Richer properties (ex: symmetrical) Class property restrictions (ex: allValuesFrom) OWL
- 24. Relationships between ClassesdisjointWith – resources belonging to one class cannot belong to the other <Person> <disjointWith> <Country> complementOf – the members of one class are all the resources that do not belong to the other <InanimateThings> <complementOf> <LivingThings> OWL
- 25. Equality sameAs – indicates that two resources actually refer to the same real-world thing or concept <wills> <sameAs> <wismith> equivalentClass – indicates that two classes have the same set of members <CoopBoardMembers> <equivalentClass> <CoopResidents> OWL
- 26. Richer Properties Symmetric – a relationship between A and B is also true between B and A <WillSmith> <marriedTo> <JadaPinkettSmith> implies <JadaPinkettSmith> <marriedTo> <WillSmith> Transitive – a relationship between A and B and between B and C is also true between A and C <piston> <isPartOf> <engine> <engine> <isPartOf> <automobile> implies <piston> <isPartOf> <automobile> OWL
- 27. Richer Properties continuedinverseOf – a relationship of type X between A and B implies a relationship of type Y between B and A <starsIn> <inverseOf> <hasStar> <MenInBlack> <hasStar> <WillSmith> implies <WillSmith> <starsIn> <MenInBlack> OWL
- 28. Class Property Restrictions– define the members of a class based on their properties allValuesFrom – resources with properties that only have values that meet this criteria Example: Property: hasParents, allValuesFrom: Human Resources that meet this criteria can be defined as also being members of the Human class someValuesFrom – resources with properties that have at least one value that meets criteria Example: Property: hasGraduated, someValuesFrom: College Resources that meet this criteria can be defined as being members of the CollegeGraduates class OWL
- 29. This seems complicated.Why do it? These capabilities allows systems to express and make sense of first order logic. All men are mortal Socrates is a man Therefore, Socrates is mortal OWL
- 30. Inferences Create newtriples based on existing triples Deduce new facts based on the stated facts <piston> <isPartOf> <engine> <engine> <isPartOf> <automobile> implies <piston> <isPartOf> <automobile> OWL
- 31. Three Flavors ofOWL OWL Lite – uses a subset of the capabilities OWL DL – uses all the capabilities, but some are used in restricted ways OWL Full – unrestricted use of capabilities; no guarantee that all resulting statements are valid OWL
- 32. SKOS = Simple Knowledge Organization System
- 33. Also based onRDF Designed specifically to express information that’s more hierarchical – broader terms, narrower terms, preferred terms and other thesaurus-like relationships Extendable into OWL, if needed SKOS
- 34.
- 35. SchemaWeb: http://www.schemaweb.info/default.aspx RDF Primer: http://www.w3.org/TR/REC-rdf-syntax/ OWL / Semantic Web: http://www.w3.org/2004/OWL/ SKOS: http://www.w3.org/2004/02/skos/ Dublin Core: http://dublincore.org/ Namespaces: http://www.w3.org/TR/REC-xml-names/ URIs: http://www.w3.org/Addressing/ Resources