[Someone]

> a universal approach to data, see RDF and SPARQL and numerous pretenders. For that matter, think of a C program where the master data structure is a graph of pointers.

A graph of typed pointers. As you likely know, the basic element of RDF is not “foo has a relationship with bar”, but “foo has a relationship with bar of type baz”.

Also, the types themselves can be part of relationships as in “baz has a relationship with quux of type foobar”

> The thing about graphs is, in general, they are amorphous and could have any structure (or lack of structure) at all which can be a disaster from a memory latency perspective

But that’s an implementation detail ;-)

In theory, the engine you use to store the graph could automatically optimize memory layout for both the data and the types of query that are run on it.

Practice is different.

> Thus practitioners tend to be skeptical about general purpose graph processing libraries

I am, too. I think the thing they’re mostly good for is producing PhD’s, both on the theory of querying them, ignoring performance, and on improving performance of implementations.

[PaulHoule]

Funny, the core table of salesforce.com is triples but they got a patent circa 2000 on a system that builds indexes and materializes views based on query profiling so the performance is good (w/ gold plated hardware). That patent is one reason why graph databases sucked for a long time.

Now the Lotus notes patents have been long expired so I’d like to see some graph database based products that can do what Notes did 30 years ago but it is lost technology like the pyramids, stonehenge and how to make HTML form applications without React.

[throwaway290]

> foo has a relationship with bar of type baz

Nope, "of type baz" is not required.

[hobofan]

Depends on the perspective. The predicate will always be an IRI. The object will either be an IRI or a literal, and all literals in RDF (as of RDF 1.1) are typed , though serialization formats like Turtle work with implied types.

There is also the option of blank nodes for objects, though in almost all implementations they are stand-ins for anonymous IRIs, so in some sense or another almost anything has "a" type.

[PaulHoule]

God the word "type" is overloaded in common discourse. For a link

   ?s ?p ?o .

you could say this is a link of "type" ?p, but technically in RDF we say ?s is of type ?type if

   ?s <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?type .

which can be abbreviated as

   ?s a ?type .

If you have RDFS inference turned on, notably, just using ?p in a triple will imply

   ?p a rdf:Property .

In plain RDF you can say a property is of some other ?type but I think you can get in trouble with that if you want to do OWL DL inference and you might want to say something like

   ?p rdfs:subPropertyOf :SomeSpecialKindOfProperty .

[throwaway290]

if baz is meant to be relationship then I was low key wrong in my comment (I thought baz was the kind of bar, which can be untyped). But I guess the relationship must be a property at least