Semantic Web Technologies: RDFS Inference

The purpose of this lab is to build an RDFS inference engine using a rule system.

Introduction

RDFS reasoning can be realized by a set of rules (See Figure 1). Therefore, RFDS reasoning can be implemented using a rule engine. Each RDF triple xxx yyy zzz . can be modeled as a (Datalog) fact.

triple(xxx, yyy, zzz)

The entailment patterns can be modeled as Datalog rules. For instance, entailment pattern rdfs2 said that

If S contains triples “aaa rdfs:domain xxx .” and “yyy aaa zzz .”, then S RDFS entails the triple “yyy rdf:type xxx .”

It can be captured by the following Datalog rule

triple(Y, "rdf:type", X) :- triple(A, "rdfs:domain", X),                            triple(Y, A, Z).

Together with the the following facts

triple(":hasTripAdvisorRating", "rdfs:domain", ":TourismObject").triple("i:ChickenHut", ":hasTripAdvisorRating", "3.5") .

We can compute all the entailed triples using a Datalog engine like DLV.

$ ~/bin/dlv rdfs-2-example.dlvDLV [build BEN+ODBC/Dec 17 2012 gcc 4.2.1 (Apple Inc. build 5666) (dot 3)]{ triple(":hasTripAdvisorRating","rdfs:domain",":TourismObject"),  triple("i:ChickenHut","rdf:type",":TourismObject"),  triple("i:ChickenHut",":hasTripAdvisorRating","3.5") }

　　　　　　　　　　　　　Figure 1: RFDS Entailment Patterns

Tasks

• Convert the tourism RDFS ontology into a Datalog file (“tourism.dlv”).

  tourism-rdfs.ttl

  @prefix : <http://example.org/term/> .@prefix i: <http://example.org/inst/> .@prefix rdf:    <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .@prefix rdfs:   <http://www.w3.org/2000/01/rdf-schema#> .@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .:Museum rdfs:subClassOf :TourismAttraction .:ArtMeseum rdfs:subClassOf :Museum .:ModernArtMuseum rdfs:subClassOf :ArtMeseum .:Landmark rdfs:subClassOf :TourismAttraction .:OutdoorSpot rdfs:subClassOf :TourismAttraction .:AmusementPark rdfs:subClassOf :TourismAttraction .:Restaurant rdfs:subClassOf :TourismObject .:Hotel rdfs:subClassOf :TourismObject .:TourismAttraction rdfs:subClassOf :TourismObject .:hasTripAdvisorRating rdfs:domain :TourismObject .:hasTripAdvisorRating rdfs:subPropertyOf :hasRating .i:Museion rdf:type :ModernArtMuseum .The TripAdvisor rating of Chicken Hut is 3.5.i:ChickenHut :hasTripAdvisorRating "3.5"^^xsd:decimal .

  tourism.dlv

  triple(":Museum", "rdfs:subClassOf", ":TourismAttraction") .triple(":ArtMeseum", "rdfs:subClassOf", ":Museum") .triple(":ModernArtMuseum", "rdfs:subClassOf", ":ArtMeseum") .triple(":Landmark", "rdfs:subClassOf", ":TourismAttraction") .triple(":OutdoorSpot", "rdfs:subClassOf", ":TourismAttraction") .triple(":AmusementPark", "rdfs:subClassOf", ":TourismAttraction") .triple(":Restaurant", "rdfs:subClassOf", ":TourismObject") .triple(":Hotel", "rdfs:subClassOf", ":TourismObject") .triple(":TourismAttraction", "rdfs:subClassOf", ":TourismObject") .triple(":hasTripAdvisorRating", "rdfs:domain", ":TourismObject") .triple(":hasTripAdvisorRating", "rdfs:subPropertyOf", ":hasRating") .triple("i:Museion", "rdf:type", ":ModernArtMuseum") .triple("i:ChickenHut", ":hasTripAdvisorRating", "3.5^^xsd:decimal") .

• Implement rdfs2, rdfs3, rdfs5, rdfs7, rdfs9, rdfs11 in Datalog (“rdfs.dlv”)

  rdfs.dlv

  % RDFS2triple(Y, "rdf:type", X) :- triple(A, "rdfs:domain", X),                            triple(Y, A, Z).% RDFS3triple(Z, "rdf:type", X) :- triple(A, "rdfs:range", X),                            triple(Y, A, Z).% RDFS5triple(X, "rdfs:subPropertyOf", Z) :- triple(X, "rdfs:subPropertyOf", Y),                                      triple(Y, "rdfs:subPropertyOf", Z).% RDFS7triple(X, B, Y) :- triple(A, "rdfs:subPropertyOf", B),                   triple(X, A, Y).% RDFS9triple(Z, "rdf:type", Y) :- triple(X, "rdfs:subClassOf", Y),                            triple(Z, "rdf:type", X).% RDFS11triple(X, "rdfs:subClassOf", Z) :- triple(X, "rdfs:subClassOf", Y),                                   triple(Y, "rdfs:subClassOf", Z).

• Test“tourism.dlv”and“rdfs.dlv”using DLV to check whether we can get all expected entailed triples.

  dlv.mingw tourism.dlv

  

  We can see that the output is the same as its original data.

  {triple(":Museum","rdfs:subClassOf",":TourismAttraction"), triple(":TourismAttraction","rdfs:subClassOf",":TourismObject"), triple(":ArtMeseum","rdfs:subClassOf",":Museum"), triple(":ModernArtMuseum","rdfs:subClassOf",":ArtMeseum"), triple(":Landmark","rdfs:subClassOf",":TourismAttraction"), triple(":OutdoorSpot","rdfs:subClassOf",":TourismAttraction"), triple(":AmusementPark","rdfs:subClassOf",":TourismAttraction"), triple(":Restaurant","rdfs:subClassOf",":TourismObject"), triple(":Hotel","rdfs:subClassOf",":TourismObject"), triple(":hasTripAdvisorRating","rdfs:domain",":TourismObject"), triple(":hasTripAdvisorRating","rdfs:subPropertyOf",":hasRating"), triple("i:Museion","rdf:type",":ModernArtMuseum"), triple("i:ChickenHut",":hasTripAdvisorRating","3.5^^xsd:decimal")}

  dlv.mingw tourism.dlv rdfs.dlv

  

  Now we can see that we successfully get all the entailed triples using DLV.

  {triple(":Museum","rdfs:subClassOf",":TourismAttraction"), triple(":Museum","rdfs:subClassOf",":TourismObject"), triple(":TourismAttraction","rdfs:subClassOf",":TourismObject"), triple(":ArtMeseum","rdfs:subClassOf",":Museum"), triple(":ArtMeseum","rdfs:subClassOf",":TourismAttraction"), triple(":ArtMeseum","rdfs:subClassOf",":TourismObject"), triple(":ModernArtMuseum","rdfs:subClassOf",":Museum"), triple(":ModernArtMuseum","rdfs:subClassOf",":TourismAttraction"), triple(":ModernArtMuseum","rdfs:subClassOf",":ArtMeseum"), triple(":ModernArtMuseum","rdfs:subClassOf",":TourismObject"), triple(":Landmark","rdfs:subClassOf",":TourismAttraction"), triple(":Landmark","rdfs:subClassOf",":TourismObject"), triple(":OutdoorSpot","rdfs:subClassOf",":TourismAttraction"), triple(":OutdoorSpot","rdfs:subClassOf",":TourismObject"), triple(":AmusementPark","rdfs:subClassOf",":TourismAttraction"), triple(":AmusementPark","rdfs:subClassOf",":TourismObject"), triple(":Restaurant","rdfs:subClassOf",":TourismObject"), triple(":Hotel","rdfs:subClassOf",":TourismObject"), triple(":hasTripAdvisorRating","rdfs:domain",":TourismObject"), triple(":hasTripAdvisorRating","rdfs:subPropertyOf",":hasRating"), triple("i:Museion","rdf:type",":Museum"), triple("i:Museion","rdf:type",":TourismAttraction"), triple("i:Museion","rdf:type",":ArtMeseum"), triple("i:Museion","rdf:type",":ModernArtMuseum"), triple("i:Museion","rdf:type",":TourismObject"), triple("i:ChickenHut",":hasTripAdvisorRating","3.5^^xsd:decimal"), triple("i:ChickenHut",":hasRating","3.5^^xsd:decimal"), triple("i:ChickenHut","rdf:type",":TourismObject")}

Analyzation

triple(":Museum", "rdfs:subClassOf", ":TourismAttraction") .triple(":TourismAttraction", "rdfs:subClassOf", ":TourismObject") .

According to RDFS11 rule

triple(X, "rdfs:subClassOf", Z) :- triple(X, "rdfs:subClassOf", Y),                                   triple(Y, "rdfs:subClassOf", Z).

here X ⇒ “:Museum”, Y ⇒ “:TourismAttraction” and Z ⇒ “:TourismObject”. So we can know that

 triple(":Museum", "rdfs:subClassOf", ":TourismObject") .