The Store and the Session

What do surf.store.Store and surf.session.Session do?

The Session establishes all conversations to the backend storage service. Resources use it to load and save their constituting triples. The Session keeps a cache of already loaded data, and it uses one or more stores to do actual loading and presistence of data.

The Store provides functions for loading and saving data, these are divided into reader and writer sub-components. Readers and writers are provided by plugins.

Preparing the store and the session

The Store and the Session objects can be instantiated as any regular Python object. Instantiation of store and session objects is illustrated below:

import surf
store = surf.Store(reader = "rdflib", writer = "rdflib")
session = surf.Session(store)

the Store is configured using its constructor arguments. reader and writer arguments specify which plugin is to be used for reading and writing RDF data. Possible values (but not limited to) for these two arguments are sparql_protocol, rdflib, allegro_franz and sesame2. Plugin-specific configuration options are also specified as constructor argument for Store. In this example, store is configured to use the sparql_protocol plugin and the address of the SPARQL HTTP endpoint is also specified:

import surf
store = surf.Store(reader = "sparql_protocol",
                   endpoint = "http://dbpedia.org/sparql")
session = surf.Session(store)

It is often convenient to load Store configuration options from file instead of specifying them in code. For example, consider an .ini file with the following contents:

[surf]
reader=sparql_protocol
endpoint=http://dbpedia.org/sparql

The following snippet loads all configuration keys from the [surf] section of the ini file and passes them to Store constructor:

import ConfigParser
import surf

config = ConfigParser.ConfigParser()
config.readfp(open("sample.ini"))
store_params = dict(config.items("surf"))
store = surf.Store(**store_params)
session = surf.Session(store)