Package org.eclipse.rdf4j.query.algebra.evaluation.federation

Interface FederatedService

All Known Implementing Classes:
RepositoryFederatedService, RepositoryFederatedService, SPARQLFederatedService, SPARQLFederatedService, TupleFunctionFederatedService
public interface FederatedService
FederatedService to allow for customized evaluation of SERVICE expression. By default SPARQLFederatedService is used.
Author:
Andreas Schwarte, James Leigh
See Also:

  • Method Details

    • ask

      boolean ask(Service service, BindingSet bindings, String baseUri) throws QueryEvaluationException

      Evaluate the provided SPARQL ASK query at this federated service. 

       Expected behavior: evaluate boolean query using the bindings as constraints
      Parameters:
      service - the reference to the service node, contains additional meta information (vars, prefixes)
      bindings - the bindings serving as additional constraints
      baseUri -
      Returns:
      true if at least one result exists
      Throws:
      QueryEvaluationException - If there was an exception generated while evaluating the query.

    • select

      CloseableIteration<BindingSet,QueryEvaluationException> select(Service service, Set<String> projectionVars, BindingSet bindings, String baseUri) throws QueryEvaluationException

      Evaluate the provided SPARQL query at this federated service.

      Important: The original bindings need to be inserted into the result. 

       Expected behavior: evaluate the given SPARQL query using the bindings as constraints
      Parameters:
      service - the reference to the service node, contains additional meta information (vars, prefixes)
      projectionVars - The variables with unknown value that should be projected from this evaluation
      bindings - the bindings serving as additional constraints
      baseUri -
      Returns:
      an iteration over the results of the query
      Throws:
      QueryEvaluationException - If there was an exception generated while evaluating the query.

    • evaluate

      CloseableIteration<BindingSet,QueryEvaluationException> evaluate(Service service, CloseableIteration<BindingSet,QueryEvaluationException> bindings, String baseUri) throws QueryEvaluationException
      Evaluate the provided SPARQL query at this federated service, possibilities for vectored evaluation.

      Contracts:

      • The original bindings need to be inserted into the result
      • SILENT service must be dealt with in the method

      Compare SPARQLFederatedService for a reference implementation

      Parameters:
      service - the reference to the service node, contains information to construct the query
      bindings - the bindings serving as additional constraints (for vectored evaluation)
      baseUri - the baseUri
      Returns:
      the result of evaluating the query using bindings as constraints, the original bindings need to be inserted into the results!
      Throws:
      QueryEvaluationException - If there was an exception generated while evaluating the query.

    • isInitialized

      boolean isInitialized()
      Method to check if initialize() had been called.

    • initialize

      void initialize() throws QueryEvaluationException
      Method to perform any initializations, invoked after construction.
      Throws:
      QueryEvaluationException - If there was an exception generated while initializing the service.

    • shutdown

      void shutdown() throws QueryEvaluationException
      Method to perform any shutDown code, invoked at unregistering.
      Throws:
      QueryEvaluationException - If there was an exception generated while shutting down the service.