Ontologies in RDF-S/OWL

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  • 07/04/10 © 2005 - Della Valle - CEFRIEL
  • 07/04/10 © 2005 - Della Valle - CEFRIEL
  • 07/04/10 © 2005 - Della Valle - CEFRIEL
  • 07/04/10 © 2005 - Della Valle - CEFRIEL
  • @prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> . @prefix ex: <http://www.ex.org/schema#> . @prefix owl: <http://www.w3.org/2002/07/owl#> . ex:Artist a owl:Class . ex:Piece a owl:Class . ex:Sculptor a owl:Class . ex:Sculptor rdfs:subClassOf ex:Artist . ex:creates a owl:ObjectProperty . ex:creates rdfs:domain ex:Artist . ex:Rodin a ex:Sculptor . ex:TheKiss a ex:Piece . ex:Rodin ex:creates ex:TheKiss .
  • <RDF> <Description about="Rodin"> <sculpts resource="TheKiss"/> </Description> <Description about="Painting"> <subClassOf resource="Piece"/> </Description> <Description about="sculpts"> <range resource="Sculpt"/> <domain resource="Sculptor"/> <subPropertyOf resource="creates"/> </Description> <Description about="Sculpt"> <subClassOf resource="Piece"/> </Description> <Description about="creates"> <range resource="Piece"/> <domain resource="Artist"/> </Description> <Description about="Sculptor"> <subClassOf resource="Artist"/> </Description> <Description about="Painter"> <subClassOf resource="Artist"/> </Description> </RDF> RDF/Description[@about='Rodin']/sculpts/@resource RDF/Description[sculpts/@resource='TheKiss']/@about
  • Ontologies in RDF-S/OWL

    1. 1. <ul><li>Emanuele Della Valle </li></ul><ul><li>[email_address] </li></ul><ul><li>http://emanueledellavalle.org </li></ul>Ontologies in RDF-S/OWL
    2. 2. Share, Remix, Reuse — Legally <ul><li>This work is licensed under the Creative Commons Attribution 3.0 Unported License. </li></ul><ul><li>Your are free: </li></ul><ul><ul><li>to Share — to copy, distribute and transmit the work </li></ul></ul><ul><ul><li>to Remix — to adapt the work </li></ul></ul><ul><li>Under the following conditions </li></ul><ul><ul><li>Attribution — You must attribute the work by inserting </li></ul></ul><ul><ul><ul><li>“ © applied-semantic-web.org” at the end of each reused slide </li></ul></ul></ul><ul><ul><ul><li>a credits slide stating: these slides are partially based on “Ontologies in RDF-S/OWL” by Emanuele Della Valle http://applied-semantic-web.org/2010/03/03_RDFS-OWL.ppt </li></ul></ul></ul><ul><li>To view a copy of this license, visit http://creativecommons.org/licenses/by/3.0/ </li></ul>
    3. 3. Ontology: RDF-S and OWL
    4. 4. RDF-S/OWL in a nutshell Ontology definition <ul><li>Philosophy (400BC): </li></ul><ul><ul><li>Systematic explanation of Existence </li></ul></ul><ul><li>Neches (91): </li></ul><ul><ul><li>Ontology defines basic terms and relations comprising the vocabulary of a topic area as well as the rules for combining terms and relations to define extensions to the vocabulary </li></ul></ul><ul><li>Gruber (93): </li></ul><ul><ul><li>Explicit specification of a conceptualization </li></ul></ul><ul><li>Borst (97): </li></ul><ul><ul><li>Formal specification of a shared conceptualization </li></ul></ul><ul><li>Studer(98) </li></ul><ul><ul><li>Formal, explicit specification of a shared conceptualization </li></ul></ul>
    5. 5. RDF-S/OWL in a nutshell What does it mean? Formal, explicit specification of a shared conceptualization Machine readable Several people agrees that such conceptual model is adequate to describe such aspects of the reality A conceptual model of some aspects of the reality It makes domain assumption explicit
    6. 6. RDF-S/OWL in a nutshell Questa è un’ontologia? <ul><li>NO, perchè </li></ul><ul><ul><li>È una concettualizzazione </li></ul></ul><ul><ul><li>È condivisa dalla comunità che l’ha sviluppata </li></ul></ul><ul><li>… ma non è </li></ul><ul><ul><li>esplicita (la dimensione dei rami molto probabilmente non indica la numerosità delle speci) </li></ul></ul><ul><ul><li>formale (nessuna macchina può usarla) </li></ul></ul>
    7. 7. RDF-S/OWL in a nutshell Esempio di ontologia <ul><li>Concetti e relazioni primitivi </li></ul><ul><ul><li>essere umano </li></ul></ul><ul><ul><li>maschio </li></ul></ul><ul><ul><li>femmina </li></ul></ul><ul><ul><li>ha figlio </li></ul></ul><ul><li>Concetti e relazioni derivate </li></ul><ul><ul><li>un uomo è un essere umano ed è un maschio </li></ul></ul><ul><ul><li>una donna è un essere umano ed è una femmina </li></ul></ul><ul><ul><li>una madre è una donna che ha almeno un figlio </li></ul></ul><ul><ul><li>una padre è un uomo che ha almeno un figlio </li></ul></ul><ul><ul><li>un genitore è o un padre o una madre </li></ul></ul><ul><ul><li>un nonno è un uomo che ha almeno un figlio che è un genitore </li></ul></ul><ul><ul><li>“ essere figlio di ” è la relazione inversa a “avere un figlio” </li></ul></ul><ul><li>Fatti asseriti </li></ul><ul><ul><li>Antonio , Lorenzo e Carlo sono uomini </li></ul></ul><ul><ul><li>Rosanna è una donna </li></ul></ul><ul><ul><li>Antonio ha figlio Lorenzo </li></ul></ul><ul><ul><li>Rosanna ha figlio Carlo </li></ul></ul><ul><ul><li>Carlo è figlio di Lorenzo </li></ul></ul><ul><ul><li>Una macchina in grado di “capire” un linguaggio ontologico “sa inferire” </li></ul></ul><ul><ul><li>Concetti: un nonno è un genitore </li></ul></ul><ul><ul><li>Fatti: Antonio è un nonno, Lorenzo è un padre, Rosanna è una madre </li></ul></ul>
    8. 8. RDF-S/OWL in a nutshell Linguaggio Ontologico <ul><li>Concetti e relazioni primitivi </li></ul><ul><ul><li>essere umano </li></ul></ul><ul><ul><li>maschio </li></ul></ul><ul><ul><li>femmina </li></ul></ul><ul><ul><li>ha figlio </li></ul></ul><ul><li>Concetti e relazioni derivate </li></ul><ul><ul><li>un uomo è un essere umano ed è un maschio </li></ul></ul><ul><ul><li>una donna è un essere umano ed è una femmina </li></ul></ul><ul><ul><li>una madre è una donna che ha almeno un figlio </li></ul></ul><ul><ul><li>una padre è un uomo che ha almeno un figlio </li></ul></ul><ul><ul><li>un genitore è o un padre o una madre </li></ul></ul><ul><ul><li>un nonno è un uomo che ha almeno un figlio che è un genitore </li></ul></ul><ul><ul><li>“ essere figlio di” è la relazione inversa a “avere un figlio” </li></ul></ul><ul><li>Fatti asseriti </li></ul><ul><ul><li>Antonio , Lorenzo e Carlo sono uomini </li></ul></ul><ul><ul><li>Rosanna è una donna </li></ul></ul><ul><ul><li>Antonio ha figlio Lorenzo </li></ul></ul><ul><ul><li>Rosanna ha figlio Carlo </li></ul></ul><ul><ul><li>Carlo è figlio di Lorenzo </li></ul></ul><ul><ul><li>Una macchina in grado di “capire” un linguaggio ontologico “sa inferire” </li></ul></ul><ul><ul><li>Concetti: un nonno è un genitore </li></ul></ul><ul><ul><li>Fatti: Antonio è un nonno, Lorenzo è un padre, Rosanna è una madre </li></ul></ul>
    9. 9. RDF-S/OWL in a nutshell Le parti di un linguaggio ontologico <ul><li>concetti </li></ul><ul><ul><li>astrazioni del dominio applicativo tipicamente visti come insiemi </li></ul></ul><ul><li>relazioni </li></ul><ul><ul><li>esprimono l’esistenza di relazioni tra i concetti del dominio tipicamente viste come relazioni binarie tra gli individui </li></ul></ul><ul><li>assiomi </li></ul><ul><ul><li>formalizzano quali combinazioni di concetti e relazioni sono ammissibili </li></ul></ul><ul><li>individui </li></ul><ul><ul><li>elementi degli insiemi definiti dai concetti </li></ul></ul><ul><li>asserzioni </li></ul><ul><ul><li>dichiarano l’appartenenza di un individuo ad un insieme </li></ul></ul><ul><li>fatti </li></ul><ul><ul><li>legano due individui tramite una relazione </li></ul></ul>
    10. 10. RDF-S/OWL in a nutshell Strong vs. Weak Semantics? “ A little semantics , goes a long way” [James Hendler, 2001] “ A Little Semantic Web Goes a Long Way in Biology” [ Wolstencroft et al., 2005]
    11. 11. RDF-S/OWL in a nutshell A simple ontology Artist Piece Painter Paint paints Sculptor Sculpt sculpts creates
    12. 12. RDF-S/OWL in a nutshell Specifying classes, sub-classes and instances <ul><li>Creating a class </li></ul><ul><ul><li>RDFS: Artist rdf:type owl:Class . </li></ul></ul><ul><ul><li>FOL:  x Artist(x) </li></ul></ul><ul><li>Creating a subclass </li></ul><ul><ul><li>RDFS: Painter rdfs:subClassOf Artist . </li></ul></ul><ul><ul><li>RDFS: Sculptor rdfs:subClassOf Artist . </li></ul></ul><ul><ul><li>FOL:  x [Painter(x)  Sculptor(x)  Artist(x)] </li></ul></ul><ul><li>Creating an instance </li></ul><ul><ul><li>RDFS: Rodin rdf:type Sculptor . </li></ul></ul><ul><ul><li>FOL: Sculptor(Rodin) </li></ul></ul>Artist Painter Sculptor Rodin
    13. 13. <ul><li>Creating a property </li></ul><ul><ul><li>RDFS: creates rdf:type owl:ObjectProperty . </li></ul></ul><ul><ul><li>FOL:  x  y Creates(x,y) </li></ul></ul><ul><li>Using a property </li></ul><ul><ul><li>RDFS: Rodin creates TheKiss . </li></ul></ul><ul><ul><li>FOL: Creates(Rodin, TheKiss) </li></ul></ul><ul><li>Creating subproperties </li></ul><ul><ul><li>RDFS: paints rdfs:subPropertyOf creates . </li></ul></ul><ul><ul><li>FOL:  x  y [Paints(x,y)  Creates(x,y)] </li></ul></ul><ul><ul><li>RDFS: sculpts rdfs:subPropertyOf creates . </li></ul></ul><ul><ul><li>FOL:  x  y [Sculpts(x,y)  Creates(x,y)] </li></ul></ul>RDF-S/OWL in a nutshell Specifying properties and sub-properties - - creates paints
    14. 14. <ul><li>È abbastanza importante parlare di OWL import e la parte di metadati di un’ontologia altrimenti non si possono validare le ontologie con http://owl.cs.manchester.ac.uk/validator/ </li></ul>
    15. 15. RDF-S/OWL in a nutshell Specifying domain/range constrains <ul><li>Checking which classes and properties can be use together </li></ul><ul><li>RDFS: </li></ul><ul><ul><li>creates rdfs:domain Artist . </li></ul></ul><ul><ul><li>creates rdfs:range Piece . </li></ul></ul><ul><ul><li>paints rdfs:domain Painter . </li></ul></ul><ul><ul><li>paints rdfs:range Paint . </li></ul></ul><ul><ul><li>sculpts rdfs:domain Sculptor . </li></ul></ul><ul><ul><li>sculpts rdfs:range Sculpt . </li></ul></ul><ul><li>FOL: </li></ul><ul><ul><li> x  y [Creates(x,y)  Artist(x)  Piece(y)] </li></ul></ul><ul><ul><li> x  y [Paints(x,y)  Painter(x)  Paint(y)] </li></ul></ul><ul><ul><li> x  y [Sculpts(x,y)  Sculptor(x)  Sculpt(y)] </li></ul></ul>
    16. 16. RDF-S/OWL in a nutshell The ontology we specified Artist Piece Painter Paint paints Sculptor Sculpt sculpts creates
    17. 17. RDF-S/OWL in a nutshell RDF-S semantics (a part of it) <ul><li>if then </li></ul><ul><ul><li>x rdfs:subClassOf y . a rdf:type y . a rdf:type x . </li></ul></ul><ul><ul><li>x rdfs:subClassOf y . x rdfs:subClassOf z . y rdfs:subClassOf z . </li></ul></ul><ul><ul><li>x a y . x b y . a rdfs:subPropertyOf b . </li></ul></ul><ul><ul><li>a rdfs:subPropertyOf b . a rdfs:subPropertyOf c . b rdfs:subPropertyOf c . </li></ul></ul><ul><ul><li>x a y . x rdf:type z . a rdfs:domain z . </li></ul></ul><ul><ul><li>x a u . u rdf:type z . a rdfs:range z . </li></ul></ul><ul><ul><li>Read out more in RDF Semantics http://www.w3.org/TR/rdf-mt/ </li></ul></ul>
    18. 18. RDF-S/OWL in a nutshell RDF-S semantics at work <ul><li>Shared the ontology ... </li></ul><ul><ul><li>@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> . </li></ul></ul><ul><ul><li>@prefix ex: <http://www.ex.org/schema#> . </li></ul></ul><ul><ul><li>ex:Sculptor rdfs:subClassOf ex:Artist . </li></ul></ul><ul><ul><li>ex:Painter rdfs:subClassOf ex:Artist . </li></ul></ul><ul><ul><li>ex:Sculpt rdfs:subClassOf ex:Piece. </li></ul></ul><ul><ul><li>ex:Painting rdfs:subClassOf ex:Piece . </li></ul></ul><ul><ul><li>ex:creates rdfs:domain ex:Artist . </li></ul></ul><ul><ul><li>ex:creates rdfs:range ex:Piece. </li></ul></ul><ul><ul><li>ex:sculpts rdfs:subPropertyOf ex:creates . </li></ul></ul><ul><ul><li>ex:sculpts rdfs:domain ex:Sculptor . </li></ul></ul><ul><ul><li>ex:sculpts rdfs:range ex:Sculpt . </li></ul></ul><ul><li>... when transmitting the following triple … </li></ul><ul><ul><li>ex:Rodin ex:sculpts ex:TheKiss . </li></ul></ul>
    19. 19. RDF-S/OWL in a nutshell Without Inference <ul><li>A recipient, that only understands XML syntax, </li></ul><ul><li>receiving </li></ul><ul><ul><ul><li><RDF> </li></ul></ul></ul><ul><ul><ul><li><Description about=&quot;Rodin&quot;> </li></ul></ul></ul><ul><ul><ul><li><sculpts resource=&quot;TheKiss&quot;/> </li></ul></ul></ul><ul><ul><ul><li></Description> </li></ul></ul></ul><ul><ul><ul><li></RDF> </li></ul></ul></ul><ul><li>can answer the following queries </li></ul><ul><ul><li>What does Rodin sculpt? </li></ul></ul><ul><ul><ul><li>RDF/Description[@about='Rodin']/sculpts/@resource </li></ul></ul></ul><ul><ul><li>Who does sculpt TheKiss? </li></ul></ul><ul><ul><ul><li>RDF/Description[sculpts/@resource='TheKiss']/@about </li></ul></ul></ul><ul><ul><li>Try out your self at http://www.mizar.dk/XPath/ </li></ul></ul><ul><li>but it cannot answer </li></ul><ul><ul><li>Who is Rodin? </li></ul></ul><ul><ul><li>What is TheKiss? </li></ul></ul><ul><ul><li>Is there any Sculptor/Scupts? </li></ul></ul><ul><ul><li>Is there any Artist/Piece? </li></ul></ul>
    20. 20. RDF-S/OWL in a nutshell Knowing the ontology and RDF-S semantics … <ul><li>A recipient, that knows the ontology and “understands” RDF semantics , </li></ul><ul><ul><li>Receiving Rodin sculpts TheKiss . </li></ul></ul>Rodin TheKiss Artist Piece Painter Paint paints Sculptor Sculpt sculpts creates
    21. 21. RDF-S/OWL in a nutshell … a reasoner can answer <ul><li>the previous queries </li></ul><ul><ul><li>What does Rodin sculpt? </li></ul></ul><ul><ul><ul><li>ex:TheKiss </li></ul></ul></ul><ul><ul><li>Who does sculpt TheKiss? </li></ul></ul><ul><ul><ul><li>ex:Rodin </li></ul></ul></ul><ul><li>it can also answer </li></ul><ul><ul><li>Who is Rodin? </li></ul></ul><ul><ul><ul><li>ex:Artist, ex:Sculptor, rdfs: Resource </li></ul></ul></ul><ul><ul><li>What is TheKiss? </li></ul></ul><ul><ul><ul><li>ex:Sclupt, ex:Piece, rdfs: Resource </li></ul></ul></ul><ul><ul><li>Is there any Sculptor? </li></ul></ul><ul><ul><ul><li>ex:Rodin </li></ul></ul></ul><ul><ul><li>Is the any Artist? </li></ul></ul><ul><ul><ul><li>ex:Rodin </li></ul></ul></ul><ul><ul><li>Is there any Sculpt? </li></ul></ul><ul><ul><ul><li>ex:TheKiss </li></ul></ul></ul><ul><ul><li>Is there any Piece? </li></ul></ul><ul><ul><ul><li>ex:TheKiss </li></ul></ul></ul><ul><ul><li>Is there any Paint? </li></ul></ul><ul><ul><ul><li>0 results </li></ul></ul></ul><ul><ul><li>Is there any Painter? </li></ul></ul><ul><ul><ul><li>0 results </li></ul></ul></ul>
    22. 22. RDF-S/OWL in a nutshell More expressive power 1/3 <ul><li>RDFS is a light ontological language that allows for defining simple vocabularies. </li></ul><ul><li>One may want also express </li></ul><ul><ul><li>Cardinality constrains (max, min, exactly) for properties usage </li></ul></ul><ul><ul><ul><li>Es. a Polygon has 3 or more edges </li></ul></ul></ul><ul><ul><ul><li> x [Polygon(x)  ≥3y Edge(y)  Forms(y,x) ] </li></ul></ul></ul><ul><ul><li>Property types </li></ul></ul><ul><ul><ul><li>transitive </li></ul></ul></ul><ul><ul><ul><ul><li>e.g. hasAncestor is a transitive property: if A hasAncestor B and B hasAncestor C , then A hasAncestor C . </li></ul></ul></ul></ul><ul><ul><ul><ul><li> x  y  z [HasAncestor(x,y)  HasAncestor(y,z)  HasAncestor(x,z) ] </li></ul></ul></ul></ul><ul><ul><ul><li>inverse </li></ul></ul></ul><ul><ul><ul><ul><li>e.g. sclupts has isSculptedBy as inverse property: if A sclupts B then B isSculptedBy A </li></ul></ul></ul></ul><ul><ul><ul><ul><li> x  y [Sculpts(x,y)  IsSculptedBy(y,x) ] </li></ul></ul></ul></ul>
    23. 23. RDF-S/OWL in a nutshell More expressive power 2/3 <ul><ul><ul><li>simmetric </li></ul></ul></ul><ul><ul><ul><ul><li>e.g. isCloseTo is a simmetric property: if A isCloseTo B then B isCloseTo A </li></ul></ul></ul></ul><ul><ul><ul><ul><li> x  y [IsCloseTo(x,y)  IsCloseTo(y,x) ] </li></ul></ul></ul></ul><ul><ul><li>Restrictions of usage for a specific property </li></ul></ul><ul><ul><ul><li>All values of property must be of a certain kind </li></ul></ul></ul><ul><ul><ul><ul><li>e.g. a D.O.C. Wine can be only produced by a Certified Wienery </li></ul></ul></ul></ul><ul><ul><ul><ul><li> x  y [DOCWine(x)  Produces(x,y)  CertifiedWienery(y)] </li></ul></ul></ul></ul><ul><ul><ul><li>Some values of property must be of a certain kind </li></ul></ul></ul><ul><ul><ul><ul><li>e.g. a Famous Painter must have painted some Famous Painting </li></ul></ul></ul></ul><ul><ul><ul><ul><li> x [FamousPainter(x)   y FamousPaint(y)  IsPaintedBy(y,x)] </li></ul></ul></ul></ul><ul><ul><li>A class is defined combining other classes (union, intersection, negation, ...) </li></ul></ul><ul><ul><ul><li>A white wine is a Wine and its color is “white” </li></ul></ul></ul><ul><ul><ul><li> x [Wine(x)  White(x)] </li></ul></ul></ul>
    24. 24. RDF-S/OWL in a nutshell More expressive power 3/3 <ul><ul><li>Two instances refers to the same real object </li></ul></ul><ul><ul><ul><li>“ The Boss” and “Bruce Springsteen” are two names for the same person </li></ul></ul></ul><ul><ul><ul><li>TheBoss = BruceSpringsteen </li></ul></ul></ul><ul><ul><li>Two classes refers to the same set </li></ul></ul><ul><ul><ul><li>“ Painters” in english and “Pittori” in italian </li></ul></ul></ul><ul><ul><ul><li> x [Painter(x)  Pittore(x)] </li></ul></ul></ul><ul><ul><li>Two properties refers to the same binary relationship </li></ul></ul><ul><ul><ul><li>“ Paints” in english and “Dipinge” in italian </li></ul></ul></ul><ul><ul><ul><li> x  y [Paints(x,y)  Dipinge(x,y)] </li></ul></ul></ul>
    25. 25. RDF-S/OWL in a nutshell Expressivity vs. Tractability <ul><li>The more an ontological language is expressive the less is tractable </li></ul><ul><li>the Web Ontology Language (OWL) comes with several profiles that offers different trade-offs between expressivity and tractability. </li></ul>
    26. 26. RDF-S/OWL in a nutshell OWL 2 profiles <ul><li>OWL 1 defines only one fragment (OWL Lite) </li></ul><ul><ul><li>And it isn’t very tractable! </li></ul></ul><ul><li>OWL 2 defines several different fragments with </li></ul><ul><ul><li>Useful computational properties </li></ul></ul><ul><ul><ul><li>E.g., reasoning complexity in range LOGSPACE to PTIME </li></ul></ul></ul><ul><ul><li>Useful implementation possibilities </li></ul></ul><ul><ul><ul><li>E.g., Smaller fragments implementable using RDBs </li></ul></ul></ul><ul><li>OWL 2 profiles </li></ul><ul><ul><li>OWL 2 EL, OWL 2 QL, OWL 2 RL </li></ul></ul>
    27. 27. RDF-S/OWL in a nutshell OWL 2 EL <ul><li>Useful for applications employing ontologies that contain very </li></ul><ul><li>large number of properties and/or classes </li></ul><ul><ul><li>Captures expressive power used by many large-scaleontologies E.g.; SNOMED CT, NCI thesaurus </li></ul></ul><ul><li>Features </li></ul><ul><ul><li>Included: existential restrictions, intersection, subClass,equivalentClass, disjointness, range and domain, object property inclusion possibly involving property chains, and data property inclusion, transitive properties, keys … </li></ul></ul><ul><ul><li>Missing: include value restrictions, Cardinality restrictions (min, max and exact), disjunction and negation </li></ul></ul><ul><li>Maximal language for which reasoning (including query answering) known to be worst-case polynomial </li></ul>
    28. 28. RDF-S/OWL in a nutshell OWL 2 QL <ul><li>Useful for applications that use very large volumes of data, and where query answering is the most important task </li></ul><ul><li>Captures expressive power of simple ontologies like thesauri, classifications, and (most of) expressive power of ER/UML schemas </li></ul><ul><li>E.g., CIM10, Thesaurus of Nephrology, ... </li></ul><ul><li>Features </li></ul><ul><ul><li>Included: limited form of existential restrictions, subClass, equivalentClass, disjointness, range & domain, symmetric properties, … </li></ul></ul><ul><ul><li>Missing: existential quantification to a class, self restriction, nominals, universal quantification to a class, disjunction etc. </li></ul></ul><ul><li>Can be implemented on top of standard relational DBMS </li></ul><ul><li>Maximal language for which reasoning (including query answering) is known to be worst case logspace (same as DB) </li></ul>
    29. 29. RDF-S/OWL in a nutshell OWL 2 RL <ul><li>Useful for applications that require scalable reasoning without sacrifying too much expressive power, and where query answering is the most important task </li></ul><ul><li>Support most OWL features but </li></ul><ul><ul><li>with restrictions placed on the syntax of OWL 2 </li></ul></ul><ul><ul><li>standard semantics only apply when they are used in a restricted way </li></ul></ul><ul><li>Can be implemented on top of rule extended DBMS </li></ul><ul><ul><li>E.g., Oracle’s OWL Prime implemented using forward chaining rules in Oracle 11g </li></ul></ul><ul><ul><li>Related to DLP and pD* </li></ul></ul><ul><li>Allows for scalable ( polynomial) reasoning using rule-based technologies </li></ul>
    30. 30. RDF-S/OWL in a nutshell RDF -S/OWL Resources <ul><li>OWL Frequently Asked Questions </li></ul><ul><ul><li>http://www.w3.org/2003/08/owlfaq.html </li></ul></ul><ul><li>RDF-S/OWL implementations - community maintained list of open-source and commercial SPARQL engines </li></ul><ul><ul><li>http://esw.w3.org/topic/SemanticWebTools#head-d07454b4f0d51f5e9d878822d911d0bfea9dcdfd </li></ul></ul><ul><li>RDF-S Specification </li></ul><ul><ul><li>http://www.w3.org/TR/rdf-schema/ </li></ul></ul><ul><li>OWL Working Group Wiki </li></ul><ul><ul><li>http://www.w3.org/2007/OWL/wiki </li></ul></ul>

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