Add key mappingRelation to isAbout and valueReference

[Ludee]

Summary of the discussion

Improve the ontology annotation with matching from SKOS.
SKOS offers standardized terms:
https://www.w3.org/TR/skos-reference/#mapping

Type of change (CHANGELOG.md)

Added

• Add mappingRelation to isAbout (#307)
• Add mappingRelation to valueReference (#307)

Workflow checklist

Automation

Closes #302 / Part of #296

PR-Assignee

• 🐙 Follow the workflow in CONTRIBUTING.md
• 📝 Update the CHANGELOG.md
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Reviewer

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• 🐙 Provided feedback and show sufficient appreciation for the work done

[Cpprentice]

I was wondering what we get out of the JSON-LD semantically if we use skos like this. I think currently we get a triple that says our isAbout blank object has a skos:mappingRelation to a string literal. What we want to express with that is rather that the value in the string should be treated as the actual predicate of that triple towards the isAbout term placed in "@id".

So semantically we should rather replace the isAbout property with the actual names of the skos properties:
So instead of :

{
    "isAbout": [
        { "@id": "http://other.stuff", "label": "troll"},
        { "@id": "http://more.stuff"}
    ]
}

{
    "exactMatch": [
        { "@id": "http://other.stuff", "label": "troll"}
    ],
    "narrowMatch": [
        { "@id": "http://more.stuff"}
    ]
}

But that would probably affect everything that relies on isAbout. So I am not sure this is wise (though semantically correct).

[jh-RLI]

We can still implement these changes in the new version. isAbout, etc., are mainly used in the SemanticMapping for Ontop; so it should certainly be feasible to adapt the relevant functions to use SKOS terms. We won’t break anything right away due to the versioning, but I agree that this will increase the effort required to implement the new Oemetadata version in the OEP and the tools.

[Ludee]

That is a good point.
The information is the same, but it would break all existing mechanism.