There are several possibilities to store RDF(S). RDF Graphs can be represented as a set of Triples, i.e. Subject, Predicate and Object. Of course these sets can simply be stored in a Relational Database Management System, for example in a single Table with a column for Subject, Predict and Object. It benefits from the very developed system of Relational Databases. However one has to convert the SPARQL Queries that were formulated into SQL with respect to a given Schema. On the other hand one can then take use of the Relational Database System to answer the SQL Query that was converted. In the end one has to generate the SPARQL results from the SQL results. This is a common way to implement SPARQL on the base of a Relational Database Technology.
Triples can simply be stored in a Relational Database Management System (RDBMS)
Motivation: Use specific relational schema for RDF data and benefit from 40 years of Research in the DB community
Convert SPARQL Query to SQL Query (w.r.t. the Schema)
Vertically Portioned Tables (Binary Tables)
It is also possible to make SPARQL endpoint on top of a Graph based Database
