"zero relations" in dataset mappings (has no matching entity in)

When matching and mapping two datasets, it is common that - on both
sides - you find entities which don't have a matching entity on the
other side.
 
When that non-matching was verified intellectually, it could be valuable
to report this fact - especially to keep track of "false positives"
(e.g. matching labels, but different concepts in SKOS systems).
Basically, this states a relation between an entity - e.g., a
skos:Concept - and a set of entities - as defined e.g. by a
skos:ConceptScheme or a void:Dataset.

Are you aware of any pattern to express this in RDF?

I consider coining something like

  ext:noMatchingEntity rdfs:subPropertyOf skos:note .
 
Since the date of the above mentioned verification should be reported,
you could end up along the lines the following example

  <http://d-nb.info/gnd/4125416-8> ext:noMatchingEntity 
    [ rdf:value <http://zbw.eu/stw> ;
      dcterms:modified "2010-01-25"^^xsd:date ] .

What do you think?

Cheers, Joachim