Chapter 2. Architecture

The following figure shows the main components and APIs in Sesame and how they are built on top of each other:

Figure 2.1. The Sesame architecture

The Sesame architecture

Being an RDF-oriented framework, all parts of Sesame are to some extent related to the RDF model. This model defines interfaces for the RDF entities "URI", "blank node", "literal" and "statement".

Sesame has two main communication interfaces: the Sail API and the Repository API. The Storage And Inference Layer (Sail) API is a low level system API (or: SPI) for RDF stores and inferencers. It's purpose is to abstract from the storage details, allowing various types of storage and inference to be used.

The Repository API is a higer level API and is meant to be the main API that people can program against. It offers various methods for uploading data files, querying, and extracting and manipulating data. It comes in two flavours: local and remote. The local Repository API can be used for "local" repositories, as in "running in the same Java Virtual Machine". The remote Repository API can be used in client-server settings, where the application communicates with a Sesame server. The two flavours share a common interface so that applications can be developed to work with both local and remote repositories transparently.

Part of the Sail API is the Sail Query Model, which can be used to build object models representing queries. A query engine like the SeRQL engine takes care of parsing query strings and building such query object model from them. These query object models can then be passed to Sail objects, which take care of their evaluation.

Rio stands for "RDF I/O" and consists of a set of parsers and writers for various RDF file formats. The parsers can be used to translate RDF files to lists of statements, and the writers for the reverse operation. Rio is used by the Repository API for data import and export, but can also be used directly by applications.