de.fuberlin.wiwiss.ng4j.semwebclient
Class SemanticWebClient

java.lang.Object
  de.fuberlin.wiwiss.ng4j.impl.NamedGraphSetIO
      de.fuberlin.wiwiss.ng4j.impl.NamedGraphSetImpl
          de.fuberlin.wiwiss.ng4j.semwebclient.SemanticWebClient

All Implemented Interfaces:

NamedGraphSet

public class SemanticWebClient
extends NamedGraphSetImpl

The SematicWebClient interface enables applications to access the Semantic Web.

The Semantic Web is represended as a single, global RDF graph. The library enables applications to query this global graph using SPARQL- and find(SPO) queries. To answer queries, the library dynamically retrieves information from the Semantic Web.

During the execution of a query, information about all resources that appear in triple patterns and in the query results is dynamically loaded from the Semantic Web by:

• dereferencing the URI of each resource using the HTTP protocol,
• following all known rdf:seeAlso links for a resource.

Internally, retrieved information is represented as a set of named graphs, which allows applications to keep track of information provenance.

If the result of dereferencing a URI is a RDF graph, the graph is added as a named graph (named with the retrieval URI) to graph set.
Within each graphset there is a graph http://localhost/provenanceInformation, which contains provenance information for each retrieved graph. The graph contains a swp:sourceURL and a swp:retrievalTimestamp triple for each retrieved graph. More information about the Semantic Web Client is found on the project's website: http://sites.wiwiss.fu-berlin.de/suhl/bizer/ng4j/semwebclient/

Author:

Chris Bizer (chris@bizer.de), Richard Cyganiak (richard@cyganiak.de), Tobias Gauß (tobias.gauss@web.de)

Field Summary

String	CONFIG_ENABLEGRDDL
String	CONFIG_MAXFILESIZE
String	CONFIG_MAXGRAPHS
String	CONFIG_MAXSTEPS
String	CONFIG_MAXTHREADS
String	CONFIG_TIMEOUT

Constructor Summary

SemanticWebClient()
Creates a Semantic Web Client.

Method Summary

void	addGraph(NamedGraph graph) Adds a NamedGraph to the set.
void	addRemoteGraph(String uri) Adds a remote graph to the graphset.
Graph	asJenaGraph(Node defaultGraphForAdding) Returns the union graph of the NamedGraphSet.
void	close() Determines all retrieval threads.
SemWebIterator	find(TripleMatch pattern) Finds Triples that match a triple pattern.
void	find(TripleMatch pattern, TripleListener listener) Finds Triples that match a triple pattern.
String	getConfig(String option) Returns the value of a given configuration option.
boolean	isClosed() Returns true if the SemanticWebCliend is already closed false if not.
void	reloadRemoteGraph(String uri) Reloads a remote graph.
boolean	requestDereferencing(String uri, int step, DereferencingListener listener) Initiates a new retrieval process for a given uri.
void	setConfig(String option, String value) Sets a configuration option.
List	successfullyDereferencedURIs() Returns an iterator over all successfully dereferenced URIs.
List	unsuccessfullyDereferencedURIs() Returns an iterator over all URIs that couldn't be dereferenced.

Methods inherited from class de.fuberlin.wiwiss.ng4j.impl.NamedGraphSetImpl

addQuad, asJenaModel, clear, containsGraph, containsGraph, containsQuad, countGraphs, countQuads, createGraph, createGraph, createNamedGraphInstance, findQuads, findQuads, getGraph, getGraph, isEmpty, listGraphs, removeGraph, removeGraph, removeQuad

Methods inherited from class de.fuberlin.wiwiss.ng4j.impl.NamedGraphSetIO

read, read, read, write, write

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface de.fuberlin.wiwiss.ng4j.NamedGraphSet

read, read, read, write, write

Field Detail

CONFIG_MAXSTEPS

public String CONFIG_MAXSTEPS

CONFIG_MAXTHREADS

public String CONFIG_MAXTHREADS

CONFIG_TIMEOUT

public String CONFIG_TIMEOUT

CONFIG_MAXGRAPHS

public String CONFIG_MAXGRAPHS

CONFIG_MAXFILESIZE

public String CONFIG_MAXFILESIZE

CONFIG_ENABLEGRDDL

public String CONFIG_ENABLEGRDDL

Constructor Detail

SemanticWebClient

public SemanticWebClient()

Creates a Semantic Web Client.

Method Detail

find

public SemWebIterator find(TripleMatch pattern)

Finds Triples that match a triple pattern. The argument may contain wildcards (Node.ANY). The implementation of the find method uses multithreading, thus the first triples can already be used while there is still information being retrieved in the background. Returned triples have a getSource() method which returns the URL from which the triple was retrieved.

Parameters:

pattern -

Returns:

find

public void find(TripleMatch pattern,
                 TripleListener listener)

Finds Triples that match a triple pattern. The argument may contain wildcards (Node.ANY). The implementation of the find method uses multithreading, thus the first triples can already be used while there is still information being retrieved in the background. This method is called with a TripleListener as second parameter which is notified each time when a triple is found and when the retrieval process is finished.

Parameters:

pattern -

addRemoteGraph

public void addRemoteGraph(String uri)

Adds a remote graph to the graphset. The graph is retrieved by dereferencing the URI.

Parameters:

seconds -

reloadRemoteGraph

public void reloadRemoteGraph(String uri)

Reloads a remote graph. The current graph is replaced by the new graph.

Parameters:

seconds -

setConfig

public void setConfig(String option,
                      String value)

Sets a configuration option. Possible options are "maxsteps" for the maximum retrieval steps ,"timeout" for the timeout and "maxthreads" for the maximum of simultaneous working DereferencerThreads .

getConfig

public String getConfig(String option)

Returns the value of a given configuration option.

successfullyDereferencedURIs

public List successfullyDereferencedURIs()

Returns an iterator over all successfully dereferenced URIs.

unsuccessfullyDereferencedURIs

public List unsuccessfullyDereferencedURIs()

Returns an iterator over all URIs that couldn't be dereferenced.

close

public void close()

Determines all retrieval threads. Has to be called to determine a Sementic Web Client.

Specified by:

close in interface NamedGraphSet

Overrides:

close in class NamedGraphSetImpl

isClosed

public boolean isClosed()

Returns true if the SemanticWebCliend is already closed false if not.

asJenaGraph

public Graph asJenaGraph(Node defaultGraphForAdding)

Description copied from interface: NamedGraphSet

Returns the union graph of the NamedGraphSet. The graph is backed by the NamedGraphSet: Subsequent changes to one are reflected in the other.

Add operations to the union graph are all written to the default graph specified as the argument.

Delete operations remove the triple from all NamedGraphs.

Specified by:

asJenaGraph in interface NamedGraphSet

Overrides:

asJenaGraph in class NamedGraphSetImpl

Parameters:

defaultGraphForAdding - The name of the default graph used for adding triples; must be an URI

Returns:

A Graph view on the NamedGraphSet

addGraph

public void addGraph(NamedGraph graph)

Description copied from interface: NamedGraphSet

Adds a NamedGraph to the set. Will replace a NamedGraph with the same name that is already in the set.

Specified by:

addGraph in interface NamedGraphSet

Overrides:

addGraph in class NamedGraphSetImpl

Parameters:

graph - The NamedGraph to be added

requestDereferencing

public boolean requestDereferencing(String uri,
                                    int step,
                                    DereferencingListener listener)

Initiates a new retrieval process for a given uri.