Hacker News new | ask | show | jobs
by felixyz 1221 days ago
I did an interview [1] with Kevin Feeney, one of the founders (no longer active) of TerminusDb, which goes into some depth about the difference between RDF stores and (property) graph databases, where the former is more closely aligned with datalog and logic programming. There are links to a really excellent series of blog posts by Kevin on this topic in the show notes.

[1] https://thesearch.space/episodes/5-kevin-feeney-on-terminusd...
2 comments
forks 1221 days ago
I love The Search Space. Waiting patiently for new episodes!
link
felixyz 1220 days ago
Thank you! They're coming, I promise :)
link
YeGoblynQueenne 1219 days ago
Second that!
link
westurner 1221 days ago
With RDF* and SPARQL* ("RDF-star" and "SPARQL-star") how are triple (or quad) stores still distinct from property graphs?

RDFS and SHACL (and OWL) are optional in a triple store, which expects the subject and predicate to be string URIs, and there is an object datatype and optional language:

  (?s ?p ?o <datatype> [lang])

  (?subject:URI, ?predicate:URI, ?object:datatype, object_datatype, [object_language])
RDFS introduces rdfs:domain and rdfs:range type restrictions for Properties, and rdfs:Class and rdfs:subClassOf.

`a` means `rdf:type`; which does not require RDFS:

  ("#xyz", a,        "https://schema.org/Thing")
  ("#xyz", rdf:type, "https://schema.org/Thing")
Quad stores have a graph_id string URI "?g" for Named Graphs:

  (?g ?s ?p ?o)

  ("https://example.org/ns/graphs/0", "#xyz", a, "https://schema.org/Thing")

  ("https://example.org/ns/graphs/1", "#xyz", a, "https://schema.org/ScholarlyArticle")
There's a W3C CG (Community Group) revising very many of the W3C Linked Data specs to support RDF-star: https://www.w3.org/groups/wg/rdf-star

Looks like they ended up needing to update basically most of the current specs: https://www.w3.org/groups/wg/rdf-star/tools

"RDF-star and SPARQL-star" (Draft Community Group Report; 08 December 2022) https://w3c.github.io/rdf-star/cg-spec/editors_draft.html

GH topics: rdf-star, rdfstar: https://github.com/topics/rdf-star, https://github.com/topics/rdfstar

pyDatalog does datalog with SQLAlchemy and e.g. just the SQLite database: https://github.com/pcarbonn/pyDatalog ; and it is apparently superseded by IDP-Z3: https://gitlab.com/krr/IDP-Z3/

From https://twitter.com/westurner/status/1000516851984723968 :

> A feature comparison of SQL w/ EAV, SPARQL/SPARUL, [SPARQL12 SPARQL-star, [T-SPARQL, SPARQLMT,]], Cypher, Gremlin, GraphQL, and Datalog would be a useful resource for evaluating graph query languages.

> I'd probably use unstructured text search to identify the relevant resources first.

link