> "items in group A which are linked to group C via linkages to items in group B"
Relational databases are actually quite convenient for such cases because you can model each "group" of items via a database table, including potentially an associative table which provides "linkage" between items in the database. Graph-based models are generally more limited than that, e.g. RDF and SPARQL are limited to simple triples which link a "source" and a "target" entity (both of which are essentially non-typed) according to a fixed "predicate". You can sort of materialize triples and endow them with extra information, but it gets clunky.
> Relational databases are actually quite convenient for such cases
I believe that someone may have done this in a nice way but every time I've encountered it (3 times thus far), it's always ended with complex SQL and tables being bent out of shape to try and keep performance.
> RDF and SPARQL are limited to simple triples which link a "source" and a "target" entity according to a fixed "predicate"
But can also infer transitive relations based on those predicates - `A canSee B`, `B canSee C` => `A canSee C` - which is handy when you're trying to discover those relationships in your data.
> But can also infer transitive relations based on those predicates - `A canSee B`, `B canSee C` => `A canSee C` - which is handy when you're trying to discover those relationships in your data.
You can do this sort of inference in a view if you use relational databases. (A view is a sort of "virtual" table based on the result of some database query. Many databases can also materialize views for improved performance, though this can make it a bit challenging to manage updates.)
> You can do this sort of inference in a view if you use relational databases.
You'd need to use recursive queries though, I think, and there be dragons.
> [materialized views] can make it a bit challenging to manage updates
We're not using them with Postgres because refreshing materialized views is very much a blunt hammer and it'd cause more hassle than it would solve. Which is annoying because they've been great when I've used them previously.
Relational databases are actually quite convenient for such cases because you can model each "group" of items via a database table, including potentially an associative table which provides "linkage" between items in the database. Graph-based models are generally more limited than that, e.g. RDF and SPARQL are limited to simple triples which link a "source" and a "target" entity (both of which are essentially non-typed) according to a fixed "predicate". You can sort of materialize triples and endow them with extra information, but it gets clunky.