Reference : REST RDF API reference : Content negotiation
  
Content negotiation
REST RDF API supports RDF/XML, TURTLE and N3 formats. You can request any of these formats by using the standard HTTP Accept header content negotiation.When making the REST API calls, you can use these HTTP Accept header values to specify the preferred format:
 
Accept header value
Preferred format
URL extension
application/rdf+xml
rdf/xml
.rdf
application/x-turtle
rdf/turtle
.ttl
application/rdf+n3
rdf/n3
.n3
application/xml
XML
.xml
application/html
HTML
.html
For example, to view resources in the RDF or XML format, use this URL in a web browser:
http://fpserver/fp/resources/workspaces/2.rdf
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REST RDF API reference