Predicate to state "isTargetOfShape" (~ inverse of sh:targetNode)

[tfrancart]

(Original post at https://lists.w3.org/Archives/Public/public-shacl/2024Jan/0004.html)

I have a use-case that involves documenting a dataset (not necessarily validating it) against a SHACL specification. By documenting I mean provide a "summary" of the graph. To do this I would like to count the number of targets of each shape in the dataset; for this I could use a direct predicate to indicate a node is a target of a shape (e.g. "xx:isTargetOfShape") (which would then be the basis to determine if a node is not targeted by any shape). This could be seen as the inverse of sh:targetNode.