- From: Aidan Hogan <aidhog@gmail.com>
- Date: Tue, 30 Jun 2020 21:02:04 -0400
- To: semantic-web@w3.org
- Cc: Juan Sequeda <juanfederico@gmail.com>, holger@topquadrant.com
On 2020-06-30 19:48, Holger Knublauch wrote: > On 30/06/2020 23:45, Antoine Zimmermann wrote: > >> >> In passing, I'd like to add a use case for existential variables that >> has not been mentioned and is absolutely crucial: in the RDF-based >> interpretation of OWL, bnodes being existential is essential. The >> RDF-based semantics of OWL would be completely disconnected from its >> direct semantics if bnodes were not interpreted as existential variables. > > Pardon me, but RDF is a standard by itself. OWL is just one other > vocabulary with additional semantics, but it shouldn't dictate what > happens in RDF. There is for example also SPARQL and SHACL, where bnodes > are *not* existential variables but simply resources where the creator > didn't care about a URI. That's BTW exactly how objects in any > mainstream programming language work - they are essentially anonymous > resources which you can only access if you have a pointer to them. > > Eric is spot on w.r.t. the mismatch between the official specs and what > is being implemented in practice. It would be good if the official specs > would be adjusted to that reality. The logicians have dominated this > space for way too long. > > As a practical example, several years ago I spoke to a couple of > database vendors because if you uploaded an RDF file with blank nodes, > their implementations were returning new blank nodes for the same data > with each query. As a result of this, it basically wasn't possible to do > incremental graph traversals or even delete nodes that you had fetched > in previous queries. Imagine delivering such useless semantics in any > other object store or relational database... We don't have to imagine when we have nulls in relational databases: https://www.wired.com/story/null-license-plate-landed-one-hacker-ticket-hell/ (... though this is what happens *without* semantics.)
Received on Wednesday, 1 July 2020 01:02:20 UTC