RDFS OWL Pervasive Computing Research Group http pcomp

Σημασιολογικός Ιστός RDF(S) OWL Οντολογίες Pervasive Computing Research Group http: //p-comp. di. uoa. gr

Το Όραμα • Sir Tim Berners-Lee: ο δημιουργός του ΠΙ και οραματιστής του Σημασιολογικού Ιστού (ΣΙ) • Εισαγωγή τεχνολογιών γνώσης στον ΠΙ • Ορισμός: Ο ΣΙ είναι η αναπαράσταση δεδομένων στο WWW. (W 3 C) • The Semantic Web is an extension of the current web in which information is given well-defined meaning, better enabling computers and people to work in cooperation [1] Pervasive Computing Research Group http: //p-comp. di. uoa. gr

Η Στοίβα του ΣΙ Pervasive Computing Research Group http: //p-comp. di. uoa. gr

Εφαρμογή: FOAF foaf: Person rdf: type foaf: name foaf: mbox Michael Souris mailto: mm@example. com <rdf: RDF xmlns: rdf="http: //www. w 3. org/1999/02/22 -rdf-syntax-ns#" xmlns: foaf="http: //xmlns. com/foaf/0. 1/"> <foaf: Person> <foaf: name>Michael Souris</foaf: name> <foaf: mbox rdf: resource="mailto: mm@example. com" /> </foaf: Person> </rdf: RDF> Pervasive Computing Research Group http: //p-comp. di. uoa. gr

RDF Statement • Το κύριο στοιχείο αναπαράστασης γνώσης • Δυαδικές συσχετίσεις [subject] [predicate] [object] = triple Predicate Subject Object Resource or Literal Resource ~ URI Literal ~ XSD Datatypes Pervasive Computing Research Group http: //p-comp. di. uoa. gr

RDF Statements (Graph) Pervasive Computing Research Group http: //p-comp. di. uoa. gr

RDF Statements (XML) <? xml version="1. 0"? > <rdf: RDF xmlns: rdf=“…" xmlns: contact=“…"> <contact: Person rdf: about="http: //www. w 3. org/People/EM/contact#me"> <contact: full. Name>Eric Miller</contact: full. Name> <contact: mailbox rdf: resource="mailto: em@w 3. org"/> <contact: personal. Title>Dr. </contact: personal. Title> </contact: Person> </rdf: RDF> Pervasive Computing Research Group http: //p-comp. di. uoa. gr

Βασικά Στοιχεία RDF(S) rdf: type, rdfs: sub. Class. Of, rdfs: sub. Property. Of, …. Pervasive Computing Research Group http: //p-comp. di. uoa. gr

Ορισμός Κλάσεων/Ιδιοτήτων <rdfs: Class id=“Person”> </rdfs: Class> <rdfs: Class id=“Man”> <rdfs: sub. Class. Of rdf: resource="#Person"/> </rdfs: Class> <rdfs: Property id=“has. Age”> <rdfs: comment>A person’s age</rdfs: comment> <rdfs: domain resource=“#Person”/> <rdfs: range resource=“#Age. Type”/> <rdfs: Property> Pervasive Computing Research Group http: //p-comp. di. uoa. gr

Ορισμός Οντολογίας Age. Type has. Age rdfs: sub. Class. Of Teenager Person rdfs: sub. Class. Of Man rdfs: sub. Class. Of Woman Pervasive Computing Research Group http: //p-comp. di. uoa. gr

Pervasive Computing Research Group http: //p-comp. di. uoa. gr

Οντολογία • A formal, explicit specification of a shared conceptualization. (Studer 1998, original definition by Gruber in 1993) • Formal: κατανοητή από μηχανές • Explicit specification: ορίζει ρητά έννοιες, συσχετίσεις μεταξύ τους, ιδιότητές τους και περιορισμούς • Shared: είναι «κοινώς» αποδεκτή • Conceptualization: ένα αφηρημένο μοντέλο ενός φαινομένου Pervasive Computing Research Group http: //p-comp. di. uoa. gr

Βασικά Στοιχεία OWL-DL (1) • RDF Schema Features: – rdfs: Class, rdfs: sub. Class. Of, rdf: Property, rdfs: sub. Property. Of, … • Restrictions: – Restriction, all. Values. From, some. Values. From, max. Cardinality, min. Cardinality, … • Property Characteristics: – Object. Property, Datatype. Property, inverse. Of, Transitive. Property, Symmetric. Property, … • Class Axioms: – disjoint. With, equivalent. Class, … • Class Expressions: – union. Of, complement. Of, intersection. Of, … Pervasive Computing Research Group http: //p-comp. di. uoa. gr

OWL syntax DL Example Description Intersection. Of C∏D Supervisor ∏ Male All Supervisors that are Male union. Of C|_|D Supervisor |_| Manager Anything that is either Supervisor or Employee all. Values. From R. C supervisor. Male All supervisors must be of type Male some. Values. From R. C has. Son. Male At least one of the sons must be of type Male value R. {o} has. Location. Athens The location property must have the value Athens min. Cardinality n R. C 1 supervises. Employee A Supervisor supervises at least one employee max. Cardinality ≤n R. C ≤ 1 has. Manager An Employee has at most one Manager Cardinality =n R. C = 1 is. Dependent. On. Employee A Person is dependent on exactly one Employee Sub. Class. Of C⊑D Manager Employee A Manager is a kind of Employee CD Department_Task_Manager. Te chnical_Task_Manager Someone cannot be a Department_Task_Manager and a Technical_Task_Manager at the same time Disjoint. Class Pervasive Computing Research Group http: //p-comp. di. uoa. gr

Επερωτήσεις στον ΣΙ • Γλώσσες επερωτησεων RDF – RDQL, RQL, SPARQL (W 3 C) – Μερικές μοιάζουν με SQL • E. g. , search top 5 -10 named persons younger than 30 PREFIX foaf: <http: //xmlns. com/foaf/0. 1/> PREFIX ns: <http: //example. org/ns#> SELECT ? name ? mbox ? age WHERE { ? x foaf: name ? name. ? x ns: age ? age. FILTER (? age < 30). OPTIONAL { ? x foaf: mbox ? mbox. } } ORDER BY ? age DESC(? name) OFFSET 5 LIMIT 10 Pervasive Computing Research Group http: //p-comp. di. uoa. gr

Βιβλιογραφία [1] T. Berners-Lee, J. Handler, and O. Lassila: The Semantic Web, Scientific American, May 2001 [2] G. Antoniou and F. van Harmelen, “A Semantic Web Primer”, The MIT Press, 2004 [3] W 3 C Semantic Web Activity, http: //www. w 3. org/2001/sw/ Pervasive Computing Research Group http: //p-comp. di. uoa. gr