sentences:  It contains implementations of an in-memory triplestore and an on-disk triplestore, along with two separate Servlet packages that can be used to manage and provide access to these triplestores, on a permanent server.The RDF4J Rio (RDF Input/Output) package contains a simple API for Java-based RDF parsers and writers.Parsers and writers for popular RDF serialisations are distributed along with RDF4J, and users can easily extend the list by putting their parsers and writers on the Java classpath when running their application.