How to find if an artifact has links or not in DNG?
One answer
Do you mean outgoing links (those stored in DN), incoming links (stored in other applications linking to a requirement), or both?
For incoming links, since DN does not manage or persist that data, it won't be part of the RDF of a requirement and you would have to query LQE (or LDX) for that data.
For outgoing links, a GET on the requirement should produce RDF that includes the outgoing links for that requirement. You will need to use the Oslc-Core-Version=2.0 header on the GET request.