4 sesame

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4 sesame

  1. 1. + Sesame Mariano Rodriguez-Muro, Free University of Bozen-Bolzano
  2. 2. + Disclaimer  License   This work is licensed under a Creative Commons Attribution-Share Alike 3.0 License (http://creativecommons.org/licenses/by-sa/3.0/) Material for these slides has been taken from  Programming the Semantic Web (Chapter 8)  Sesame’s documentation
  3. 3. + Reading material  Programming the Semantic Web Chapter 8  Sesame user guide http://www.openrdf.org/doc/sesame2/users/  See also Jetty 8 http://download.eclipse.org/jetty/stable-8/dist/
  4. 4. + Overview
  5. 5. + Overview  Sesame  History  Overview  Repository API  Creating a Repository  Repository connections  Sesame Console  Sesame workbench
  6. 6. + Overview and History  Open source Java for storage and querying RDF  By Aduna for the On-ToKnowledge EU project  RDF inference   RDF IO (all file formats) Now developed by Nlnet foundation, Ontotext and community volunteers  JDBC-like user API  Available at www.openrdf.org  RESTful HTTP interface  SPARQL Protocol support  Easy learning curve, great management features
  7. 7. + Sesame components  RDF Model: contains all basic entities  Repository API: high level API with developer-methods  Rio: parsers and writers  HTTP Server: Java Servlets to access Sesame repos  Sail: low level API for RDF stores and inferencers (abstraction)  HTTPClient: Abstraction layer to access HTTP Servers
  8. 8. + Repository API
  9. 9. + Repository API  Developer-focused API  In contrast with Jena, in Sesame RDF models are not handled by the user (normally), instead we use Repositories.  Vendors provide triple stores as Repository implementations  Sesame provides the following repository implementations:     Main memory Native RDF repository Remote repository (HTTP proxy) To use Sesame repositories, these must be stacked in Sails, i.e., stacks of layered behavior
  10. 10. + Creating a repository  An in-memory repo Repository myRepository = new SailRepository(new MemoryStore()); myRepository.initialize();  An in-memory repo with persistance File dataDir = new File("c:tempmyRepository"); Repository myRepository = new SailRepository( new MemoryStore(dataDir) ); myRepository.initialize();
  11. 11. + Creating a repository  a native RDF repository File dataDir = new File("/path/to/datadir/"); Repository myRepository = new SailRepository(new NativeStore(dataDir)); myRepository.initialize();  a native RDF repository with custom indexes File dataDir = new File("/path/to/datadir/"); String indexes = "spoc,posc,cosp"; Repository myRepository = new SailRepository(new NativeStore(dataDir, indexes)); myRepository.initialize();
  12. 12. + Creating a repository  a remote Repository String sesameServer = "http://example.org/sesame2"; String repositoryID = "example-db"; Repository myRepository = new HTTPRepository(sesameServer, repositoryID); myRepository.initialize();
  13. 13. + Using a repository: RepositoryConnection  JDBC like-interface  Operations  add triples by file, URI, Statement  query using SPARQL SELECT, ASK or Construct queries  create, retrieve, remove individual statements  prepared queries  Transaction support  commit(), rollback()
  14. 14. + Adding to a repository File file = new File("/path/to/example.rdf"); String baseURI = "http://example.org/example/local"; try { RepositoryConnection con = myRepository.getConnection(); try { con.add(file, baseURI, RDFFormat.RDFXML); URL url = new URL("http://example.org/example/remote"); con.add(url, url.toString(), RDFFormat.RDFXML); } finally { con.close(); } } catch (…)
  15. 15. + Querying a repository (tuple) RepositoryConnection con = myRepository.getConnection(); try { String queryString = “SELECT …. “; TupleQuery tupleQuery = con.prepareTupleQuery(SPARQL, queryString); TupleQueryResult result = tupleQuery.evaluate(); try { .... // do something with the result } finally { result.close(); } } finally { con.close(); }
  16. 16. + Tuple queries (cont) while (result.hasNext()) { BindingSet bindingSet = result.next(); Value valueOfX = bindingSet.getValue("x"); Value valueOfY = bindingSet.getValue("y"); // do something interesting with the values here... } List<String> bindingNames = result.getBindingNames(); while (result.hasNext()) { BindingSet bindingSet = result.next(); Value firstValue = bindingSet.getValue(bindingNames.get(0)); Value secondValue = bindingSet.getValue(bindingNames.get(1)); // do something interesting with the values here... }
  17. 17. + TupleQueryResultHandler FileOutputStream out = new FileOutputStream("/path/to/result.srx"); try { SPARQLResultsXMLWriter sparqlWriter = new SPARQLResultsXMLWriter(out); RepositoryConnection con = myRepository.getConnection(); try { String queryString = "SELECT * FROM {x} p {y}"; TupleQuery tupleQuery = con.prepareTupleQuery(QueryLanguage.SERQL, queryString); tupleQuery.evaluate(sparqlWriter); } finally { con.close(); } } finally { out.close(); }
  18. 18. + Evaluating Graph queries GraphQueryResult graphResult = con.prepareGraphQuery( QueryLanguage.SPARQL, "CONSTRUCT ….").evaluate(); while (graphResult.hasNext()) { Statement st = graphResult.next(); // ... do something with the resulting statement here. }
  19. 19. + RDF Handler  Equivalent for TupleQueryResultHandler > RDFHandler  Examples: RDFXMLWriter, TurtleWriter, etc. TurtleWriter turtleWriter = new TurtleWriter(System.out); con.prepareGraphQuery(QueryLanguage.SPARQL, "CONSTRUCT …").evaluate(turtleWriter);
  20. 20. + Adding individual statements ValueFactory f = myRepository.getValueFactory(); URI alice = f.createURI("http://example.org/people/alice"); URI bob = f.createURI("http://example.org/people/bob"); URI name = f.createURI("http://example.org/ontology/name"); URI person = f.createURI("http://example.org/ontology/Person"); Literal bobsName = f.createLiteral("Bob"); Literal alicesName = f.createLiteral("Alice"); RepositoryConnection con = myRepository.getConnection(); con.add(alice, RDF.TYPE, person); con.add(alice, name, alicesName); con.add(bob, RDF.TYPE, person); con.add(bob, name, bobsName);
  21. 21. + Retrieving RepositoryResult<Statement> statements = con.getStatements(alice, null, null, true); try { while (statements.hasNext()) { Statement st = statements.next(); ... // do something with the statement } } finally { statements.close(); // make sure the result object is closed properly }
  22. 22. + Deleting statements  a single statement con.remove(alice, name, alicesName);  many statements con.remove(alice, null, null);
  23. 23. + Iterators and statements  Sesame’s API offer many calls compatible for iterators to facilitate “batch” manipulation // Retrieve all statements about Alice and put them in a list RepositoryResult<Statement> statements = con.getStatements(alice, null, null, true)); List<Statement> aboutAlice = Iterations.addAll(statements, new ArrayList<Statement>()); // Then, remove them from the repository con.remove(aboutAlice); con.remove(con.getStatements(alice, null, null, true));
  24. 24. + Named graphs  Named graphs are natively supported by Sesame  Named graphs are called “Context” in Sesame String location = "http://example.org/example/example.rdf"; String baseURI = location; URL url = new URL(location); URI context = f.createURI(location); con.add(url, baseURI, RDFFormat.RDFXML, context);
  25. 25. + Transactions  SQL-like transactions  Treat a “block” of operations as a single update  Failures can be “rolled back”
  26. 26. + Transactions File inputFile1 = new File("/path/to/example1.rdf"); String baseURI1 = "http://example.org/example1/"; File inputFile2 = new File("/path/to/example2.rdf"); String baseURI2 = "http://example.org/example2/"; RepositoryConnection con = myRepository.getConnection(); try { con.setAutoCommit(false); con.add(inputFile1, baseURI1, RDFFormat.RDFXML); con.add(inputFile2, baseURI2, RDFFormat.RDFXML); con.commit(); } catch (RepositoryException e) { con.rollback(); } finally { con.close(); }
  27. 27. + Sesame Console
  28. 28. + Sesame console  command-line application to interact with Sesame  Possible actions:  Easy way to create and manage repositories Create in the console, use from Java Creating repositories  Load/Unload data from Files/URIs/SPARQL Update    Query using SPARQL  Querying/Managing remote Sesame repositories > sh bin/console.sh Connected to default data directory Commands end with '.' at the end of a line Type 'help.' for help > help.
  29. 29. +  Repository types memory,memory-rdfs a memory based RDF repository (optionaly with RDFS inference) Please specify values for the following variables: Repository ID [native]: myRepo Repository title [Native store]: My repository Triple indexes [spoc,posc]: Repository created  pgsql, mysql > show repositories. a repository that stores data in a > +---------PostgreSQL (mysql) database > |SYSTEM > |myRepo(”My repository")  remote -- a repository that serves as > +--------- native, native-rdfs a repository that uses on-disk data structure (optional RDFS inference) a proxy for a repository on a Sesame Server
  30. 30. + Sesame Workbench Repository Manager and SPARQL end-points with Sesame
  31. 31. + Sesame workbench  SPARQL Protocol implementation (sparqlendpoint) for Sesame repositories  Web based management console for Sesame repositories  Web based query interface for repositories.
  32. 32. + Setup  Requires a JSP server, e.g., Tomcat or Jetty 8  Drop the 2 .war files from the /war folder of the sesame .zip into your webapps folder  Start the JSP server If you are using Jetty, do: jetty.sh/bat start in the command line

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