Scalable and Reactive Programming for Semantic Web Developers discusses using Scala for semantic web development. Key points include:- Scala allows for more concise RDF code compared to Java through features like type inference and implicit parameters.- The actor model and futures in Scala enable asynchronous and reactive programming for RDF streams and SPARQL queries. - OWL API reasoning with ontologies can be done more clearly in Scala through implicit classes that simplify common operations.

What's hot

Viewers also liked

Similar to Scala Programming for Semantic Web Developers ESWC Semdev2015

More from Jean-Paul Calbimonte

Recently uploaded

Scala Programming for Semantic Web Developers ESWC Semdev2015

• 1.
  Scalable and ReactiveProgrammingfor SemanticWeb DevelopersJean-Paul CalbimonteLSIR EPFLDevelopers Workshop. Extended Semantic Web Conference ESWC 2015Portoroz, 31.05.2015@jpcik
• 2.
  Semantic Web Devs2HavefunLove challengesNeed cool toolsSesame
• 3.
  Scala: Functions andObjects3JVM languageBoth object and functional orientedEasy Java-interopReuse Java librariesGrowing community
• 4.
  RDF in Jena:in ScalaString personURI = "http://somewhere/JohnSmith";Model model = ModelFactory.createDefaultModel();model.createResource(personURI).addProperty(VCARD.FN,"John Smith");Type inferenceNot too useful; and ()4Terser & compact codeType-safe DSLCompiler takes careval personURI = "http://somewhere/JohnSmith"val model = ModelFactory.createDefaultModelmodel.createResource(personURI).addProperty(VCARD.FN,"John Smith")sw:JohnSmith “John Smith”vcard:FNval personURI = "http://somewhere/JohnSmith"implicit val model = createDefaultModeladd(personURI,VCARD.FN->"John Smith")boilerplateString convertedto Resource
• 5.
  Some more RDF5StringpersonURI = "http://somewhere/JohnSmith";String givenName = "John";String familyName = "Smith";String fullName = givenName + " " + familyName;Model model = ModelFactory.createDefaultModel();model.createResource(personURI).addProperty(VCARD.FN,fullName).addProperty(VCARD.N,model.createResource().addProperty(VCARD.Given,givenName).addProperty(VCARD.Family,familyName));val personURI = "http://somewhere/JohnSmith"val givenName = "John"val familyName = "Smith"val fullName = s"$givenName $familyName"implicit val model = createDefaultModeladd(personURI,VCARD.FN->fullName,VCARD.N ->add(bnode,VCARD.Given -> givenName,VCARD.Family->familyName))sw:JohnSmith“John Smith”vcard:FN_:n“John”“Smith”vcard:Nvcard:Givenvcard:FamilyBlank nodeScala DSLs customizablePredicate-objects are pairs
• 6.
  Some more RDFin Jena6implicit val m=createDefaultModelval ex="http://example.org/"val alice=iri(ex+"alice")val bob=iri(ex+"bob")val charlie=iri(ex+"charlie")alice+(RDF.`type`->FOAF.Person,FOAF.name->"Alice",FOAF.mbox->iri("mailto:alice@example.org"),FOAF.knows->bob,FOAF.knows->charlie, FOAF.knows->bnode)bob+ (FOAF.name->"Bob",FOAF.knows->charlie)charlie+(FOAF.name->"Charlie",FOAF.knows->alice)Still valid Jena RDFYou can do it even nicer
• 7.
  Exploring an RDFGraph7ArrayList<String> names=new ArrayList<String>();NodeIterator iter=model.listObjectsOfProperty(VCARD.N);while (iter.hasNext()){RDFNode obj=iter.next();if (obj.isResource())names.add(obj.asResource().getProperty(VCARD.Family).getObject().toString());else if (obj.isLiteral())names.add(obj.asLiteral().getString());}val names=model.listObjectsOfProperty(VCARD.N).map{case r:Resource=>r.getProperty(VCARD.Family).obj.toStringcase l:Literal=>l.getString}Imperative iteration of collectionsType-based conditional executionType castingCase typeMap applied to operators
• 8.
  8
• 9.
  Query with SPARQL9valqueryStr = """select distinct ?Conceptwhere {[] a ?Concept} LIMIT 10"""val query = sparql(queryStr)query.serviceSelect("http://dbpedia.org/sparql").foreach{implicit qs=>println(res("Concept").getURI)}val f=Future(query.serviceSelect("http://es.dbpedia.org/sparql")).fallbackTo(Future(query.serviceSelect("http://dbpedia.org/sparql")))f.recover{case e=> println("Error "+e.getMessage)}f.map(_.foreach{implicit qs=>println(res("Concept").getValue)})Remote SPARQL endpointSimplified access toQuery solutionsFutures: asnyc executionNon blocking codeFallback alternative execution
• 10.
  Actor Model10Actor1Actor2mNo sharedmutable stateAvoid blocking operatorsLightweight objectsLoose couplingcommunicatethrough messagesmailboxstatebehaviornon-blocking responsesend: fire-forgetImplementations: e.g. Akka for Java/ScalaParentActor1SupervisionhierarchySupervisionActor2Actor4XActor2Actor1Actor2mActor3Actor4mmRemoting
• 11.
  Reactive SystemsEvent-DrivenJonas Boner.Go Reactive: Event-Driven, Scalable, Resilient & Responsive Systems. 2013.Events:reacttoScalableLoad:ResilientFailure:ResponsiveUsers:11
• 12.
  RDF Streams: Actors12valsys=ActorSystem.create("system")val consumer=sys.actorOf(Props[RdfConsumer])class Streamer extends StreamRDF{override def triple(triple:Triple){consumer ! triple}}class RdfConsumer extends Actor{def receive= {case t:Triple =>if (t.predicateMatches(RDF.‘type‘))println(s"received triple $t")}RDF consumerActor receive methodImplements behaviorMessage-passing modelRDF producerAsync message passing
• 13.
  Web RDF Services13GET/containers/:containerid/ org.rsp.ldp.ContainerApp.retrieve(containerid:String)POST /containers/:containerid/ org.rsp.ldp.ContainerApp.add(containerid:String)object ContainerApp extends Controller {def retrieve(id:String) = Action.async {implicit request=>val sw=new StringWriterval statements=m.listStatements(iri(prefix+id+"/"),null,null)val model=createDefaultModelstatements.foreach(i=>model.add(i))model.write(sw, "TURTLE")Future(Ok(sw.toString).as("text/turtle").withHeaders(ETAG->tag,ALLOW->"GET,POST"))}Routing rulesController returns RDF async
• 14.
  OWLAPI: reasoning14val onto=mgr.createOntologyvalartist=clazz(pref+"Artist")val singer=clazz(pref +"Singer")onto += singer subClassOf artistval reasoner = new RELReasonerFactory.createReasoner(onto)val elvis=ind(pref+"Elvis")reasoner += elvis ofClass singerreasoner.reclassifyreasoner.getIndividuals(artist) foreach{a=>println(a.getRepresentativeElement.getIRI)}Creating OWL classesDeclaring class relationshipsDeclare instances
• 15.
  How is itdone?15object OwlApiTips{implicit class TrowlRelReasoner(reasoner:RELReasoner){def += (axiom:OWLAxiom)= reasoner.add(Set(axiom)) }implicit class OwlClassPlus(theClass:OWLClass){def subClassOf(superclass:OWLClass)(implicit fac:OWLDataFactory)=fac.getOWLSubClassOfAxiom(theClass, superclass) }implicit class OwlOntologyPlus(onto:OWLOntology){def += (axiom:OWLAxiom)(implicit mgr:OWLOntologyManager)=mgr.addAxiom(onto, axiom) }implicit class OwlIndividualPlus(ind:OWLIndividual){def ofClass (theclass:OWLClass)(implicit fac:OWLDataFactory)=fac.getOWLClassAssertionAxiom(theclass, ind) }implicit def str2Iri(s:String):IRI=IRI.create(s)object clazz{def apply(iri:String)(implicit fac:OWLDataFactory)=fac.getOWLClass(iri) }object ind{def apply(iri:String)(implicit fac:OWLDataFactory)=fac.getOWLNamedIndividual(iri) } }
• 16.
  Muchas gracias!Jean-Paul CalbimonteLSIREPFL@jpcik