Qualified links

Hello,

I know the question of qualified linking has been discussed at length at
least a couple of times already [1], and I understand the WA model does not
provision with explicit qualified linking, but I have failed to extract
from these discussions an agreed best practice.

So please allow me to ask for further guidance : what would be in practice
the best way to qualify a linking body with an arbitrary IRI ?

Is there an existing property type that fits this usage?
Motivation looks like the way to go, but the need for subclasses of
SkosConcept [2] sounds too restrictive to be able to re-use existing
vocabularies.
Or should I use a custom "linkType" property on bodies? e.g.

{
  "type": "Annotation",
  "body": {
    "purpose" : "linking",
    "source": "http://example.org/item2.pdf",
    "selector": {
      "type": "FragmentSelector",
      "value": "page=7&xywh=323,502,241,45"
    },
    "foo:linkType" : "http:/schema.example.org/isSomehowRelatedWith"
  },
  "target": "http://example.org/item1"
}

(I know this looks very much like rdf:predicate, but I don't mean to revive
the reification debate)

Thank you,

Philippe


[1] http://lists.w3.org/Archives/Public/public-annotation/2016Jan/0107.html
[2] https://www.w3.org/TR/annotation-vocab/#extending-motivations