redland (version 1.0.17-6)

redland: Create, query and write RDF graphs.

Description

The R package redland provides methods to create, query and write information stored in the Resource Description Framework (RDF). This package is implemented as R scripts that provide an R interface (aka "wrapper") to the Redland RDF C libraries. Documentation for the redland R package classes and functions are available from the standard R help facility, for example, 'help("Node-class")', '?getNodeType', etc.

An overview of the redland R package is available with the R command: 'vignette("redland_overview")'.

The Redland C library functions are described at http://librdf.org/docs/api/index.html.

An introduction to RDF can be found at http://www.w3.org/TR/rdf-primer.

Details

The redland R package classes and the corresponding Redland C library types are shown in the following table: llll{ Concept Redland C type redland R class Purpose Resource / Literal librdf_node redland::Node RDF Model & Syntax nodes Statement / Triple librdf_statement redland::Statement RDF Model & Syntax arcs (statements, triples) [isa Resource] Model librdf_model redland::Model Set of Statements usually held in one Storage. Node librdf_node redland::Node The subject, predicate or object of a Statement Storage librdf_storage redland::Storage Storage for Models either persistant or in-memory. Parser librdf_parser redland::Parser Syntaxes parsers delivering Stream of Statements or writing to a Model Query librdf_query redland::Query Querying of an Model delivering a QueryResults QueryResults librdf_query_results redland::QueryResults Results of applying an Query to a Model giving either variable bindings with Node values or Stream of Statements Serializer librdf_serializer redland::Serializer Serializes a Model into a syntax such as RDF/XML World librdf_world redland::World RDF wrapper class handling Redland startup/shutdown }

Examples

# This example creates the necessary R objects to hold an RDF model and reads 
# in a file that contains RDF/XML statements. This model is then queried for 
# and the query results inspected.
world <- new("World")
storage <- new("Storage", world, "hashes", name="", options="hash-type='memory'")
model <- new("Model", world, storage, options="")
filePath <- system.file("extdata/example.rdf", package="redland")
parser <- new("Parser", world)
parseFileIntoModel(parser, world, filePath, model)
queryString <- paste("PREFIX dc: <http://purl.org/dc/elements/1.1/> ",
                     "SELECT ?a ?c WHERE { ?a dc:description ?c . }", sep="")
query <- new("Query", world, queryString, base_uri=NULL, 
             query_language="sparql", query_uri=NULL)
# Get first (and only, in this case) result
queryResult <- executeQuery(query, model)
result <- getNextResult(queryResult)