Triplestore
A triplestore or RDF store is a type of database built and optimized for storing Semantic triples (RDF triples) (subject–predicate–object). It can be queried through semantic queries.
See List of databases, relational databases.
Also known as storing quads where graph is fourth or zeroth -iple.
See the good answer by FrobberOfBits and some comments by Joshua Taylor on StackOverflow Graph Databases vs Triple Stores - when to use which? https://stackoverflow.com/a/30167732
References
Comparison of triplestores on Wikipedia
A comparison of information modeling in ORM and OWL (University of Oslo – UiO)