Re: the rationale and history of RDF-star semantics

How far does this history go back?  Wasn't the original semantics for RDF* a 
semantics that treats embedded triples as syntactic sugar for RDF reification?


peter



On 1/17/23 08:35, Pierre-Antoine Champin wrote:
> Dear Enrico, all,
>
> following the discussion we had during the last call [1], I would like to 
> give a more detail overview of our rationale when designing the RDF-star 
> semantics in the CG report [2], and defuse a few misunderstandings.
>
> 1. It was not the intention to make RDF-star a modal logic
>
> I know that examples such that ":alice :belives << :s :p :o >>." strongly 
> point in the direction of modal logic, and that such examples have been 
> largely used to "sell" RDF-star. I agree that such examples are misleading, 
> and we actually tried to avoid such examples in the CG report.
>
> The intention was to make RDF-star quoted triples opaque, and providing as 
> little inferences as possible -- leaving it open for semantic extensions to 
> provide more inferences.
>
>
> 2. Ground quoted triples are similar to literals
>
> Our initial attempt was to define from scratch a model theoretic semantics 
> of RDF-star, where ground quoted triples (i.e. quoted triples containing no 
> blank node) were constrained to denoted themselves. In other words, we 
> consider that RDF(-star) triples (as defined by the specification) are 
> conceptual objects that exist in the world (in the same way that graphs, 
> classes and properties exist), and that ground quoted triples did denote 
> exactly them.
>
> In that sense, ground quoted triples are very much like literals (except 
> that they are allowed in the subject position).
>
>
> 3. Blank node rain on our parade (as they usually do)
>
> Of course, things get tricky when we take blank nodes into account.
>
> Just like the RDF1.1 Semantics, our proposal was built in two steps :
> - define the semantics of ground RFD-star graphs (following the rationale 
> described above)
> - deal with blank node
>
> The second step was quite complicated, and it raised some questions about 
> whether this brand new semantics was sound. An alternative way was therefore 
> proposed, to rely on the battle-tested RDF semantics. And that's where we 
> are now.
>
> Honestly, I would rather give another try at /adapting /the current RDF 
> semantics to take into account quoted graphs, than keeping the layered 
> approach that we currently have.
>
>   pa
>
>
> [1] https://www.w3.org/2023/01/12-rdf-star-minutes.html#t03
> [2] https://www.w3.org/2021/12/rdf-star.html#rdf-star-semantics
>