Avoid the negated property path

The ! negation operator in property paths negate the match. For example:

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SELECT ?s ?o { ?s !nie:url ?o }

This query looks for every other property that is not nie:url. The same reasoning than unrestricted predicates apply, since that specific query is equivalent to:

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SELECT ?s ?o { ?s ?p ?o .
               FILTER (?p != nie:url) }