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SPARQL Endpoint

 

OntoBroker RDF supports an endpoint providing access to SPARQL Query and SPARQL Update. Therefore OntoBroker RDF can be used in context of Linked Open Data (LOD). To activate this web service, either use the OntoConfig option

SparqlEndpoint = on

or start the server with option -sparqlEndpoint. If left unchanged in the settings (option HttpPort), the default port is 8267. The path for the service is /services/sparql/query for queries and /services/sparql/update for updates. For example, if the OntoBroker web service is running on "localhost" standard port 8267, the query service is accessible via

http://localhost:8267/services/sparql/query

and the update service via

http://localhost:8267/services/sparql/update

If no parameters are supplied the debug mode showing a simple HTML based UI is activated.

To verify if the service is started you can access

http://localhost:8267/services

which provides an overview of all deployed REST or REST-style (and SOAP) services. Additionally via

http://localhost:8267/services/sparql?_wadl

a Web Application Description Language (WADL)-based specification of the service parameters and supported MIME types can be derived. Please be aware that this generated description does not reflect every detail, e.g. parameter qualifiers like required and repeating are not included.

For testing and debugging purposes the debug mode might be used. It is activated either by directly accessing the service without any arguments or explicitly setting the parameter debug to true. The lightweight HTML based UI allows you to switch between update and query mode. For queries the URI-results are linked to basic SPARQL queries thus supporting a basic navigation through the loaded data. Both the query and update services are documented in detail in the next sections.

 

Additional information about Linked Open Data (LOD):

While the traditional web links a huge amount of human readable web pages to each other the great vision of the Semantic Web creates a web of data. A light-weight version of this web of data are linked open data (LOD) sources. They collect structured information and provide this information in LOD servers. These LOD servers are accessible with the http-protocol and thus by ordinary browsers. Objects are identified by URIs.  For instance DBpedia is a system extracting information from Wikipedia and providing this information in a structured way as an LOD server.

Ontobroker can be exposed as such an LOD endpoint. Together with its integration capabilities this provides a large amount of possibilities to bring data into the linked open data cloud.