The Knowledge Graph server is based on FactForge by Ontotext. FactForge integrates a subset of the Linked Open Data cloud (LOD) and provides inference and SPARQL querying on top of it. The underlying RDF engine of FactForge is GraphDB by Ontotext.
The following Linked Datasets are available for querying via the Knowledge Graph Server (FactForge):
See http://www.ontotext.com/factforge for more info
The following ontologies and vocabularies are used:
At present, the integrated datasets provide more than 5 billion RDF triples.
Both GET and POST methods are supported. The GET method is preferred as it adheres to the REST architectural style. The POST method should be used in cases where the length of the (URL-encoded) query exceeds practicable limits of proxies, servers, etc. In case a POST request is used, the query parameters should be sent to the server as www-form-urlencoded data.
The response format depends on the query type and the selected Accept format parameter.
Let's execute the following simple SPARQL query, listing the names of all European countries (from DBpedia):
We can use a simple online tool like curl to execute the request to the RESTful service for the Knowledge Graph server:
Lets go step-by-step through the sample code above:
The result of the service invocation is a JSON file which looks like:
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