Semantic Predication: 1 - basic distinctions

As I said, I’m interested to make sure that in RDF-star there will be a sound characterisation of the class of use cases which I call “semantic predication”. It is clear that they behave homogeneously but differently from the other two classes of use cases which I call “syntactic predication” and “modal/epistemic predication”. For this reason and for simplicity, in order to avoid confusion, at this stage I will use three different notations to identify embedded triples in the three different predication classes; I will argue elsewhere why I believe that this is better than adopting other ways to distinguish the three classes.

Let me, again, summarise the difference between these three classes, via three different examples:


Semantic predication example:


<<< :john :teaches :cs101 >>> rdf:type :teaching ;
                              dct:Location dbr:Stanford_University ;
                              dct:PeriodOfTime :1st-term-2022 .


A semantic embedded triple denotes a resource that is meaningful in the domain of interest. In the above example, <<< :john :teaches :cs101 >>> denotes an instance of :teaching.


Syntactic predication example:


<< :john :teaches :cs101 >> :recorded "2021-07-07"^^xsd:date .


A syntactic embedded triple denotes a resource representing the triple itself as a syntactic object. In the above example, << :john :teaches :cs101 >> should denote an instance of something like unstar:triple and not an instance of :teaching.


Modal/epistemic predication example:


<<<< :john :teaches :cs101 >>>> :accordingTo :employee22 .


A modal/epistemic embedded triple does not denote any meaningful resource in the domain of interest, but it represents a statement which should be true in the context of the predication. For this reason, it would be wrong to let a modal/epistemic embedded triple denote a resource. As a matter of fact, a modal/epistemic embedded triple should denote a set of RDF interpretations, namely all the RDF interpretations in which the modal/epistemic embedded triple is true. This leads to a semantics for RDF-star modal/epistemic embedded triples in the style of modal logics, which clearly can not be adjusted easily as an extension of the RDF 1.1 semantics. However, in the spirit of RDF as a language capable of meta modelling, the modal/epistemic embedded triple  <<<< :john :teaches :cs101 >>>> could still denote a resource, and it would be an instance of something like unstar:statement.


Final comment:

So, the above examples show that a way to understand which class an occurrence of an embedded triple belongs to, is to ask yourself: does the occurrence of the embedded triple denote an instance of some event/state meaningful in your domain, or it denotes just the occurrence of the triple itself, or it denotes a statement which is meant to be true in the context of the predication?