RDF Data Factory
This package contains an implementation of the RDF/JS Data model. It works in both JavaScript and TypeScript.
Concretely, it provides an implementation of the following interfaces:
-
DataFactory
: A factory for instantiating RDF terms and quads. -
NamedNode
: A term that contains an IRI. -
BlankNode
: A term that represents an RDF blank node with a label. -
Literal
: A term that represents an RDF literal, containing a string with an optional language tag or datatype. -
Variable
: A term that represents a variable. -
DefaultGraph
: A singleton term instance that represents the default graph.
If using TypeScript, it is recommended to use this in conjunction with @types/rdf-js
.
Installation
$ npm install rdf-data-factory
or
$ yarn add rdf-data-factory
This package also works out-of-the-box in browsers via tools such as webpack and browserify.
Usage
It is recommended to always create terms via a DataFactory
instance:
import { DataFactory } from 'rdf-data-factory';
import * as RDF from 'rdf-js';
const factory: RDF.DataFactory = new DataFactory();
You can pass the following option to define a blank node prefix:
const factory: RDF.DataFactory = new DataFactory({ blankNodePrefix: 'bnode_' });
If no blankNodePrefix
is passed, it will generate a unique prefix of the form df_[0-9]+_
,
which ensures there will be no blank nodes clashes when instantiating multiple factories.
Creating named nodes
const term: RDF.NamedNode = factory.namedNode('http://example.org');
console.log(term.value); // 'http://example.org'
console.log(term.termType); // 'NamedNode'
console.log(term.equals(term)); // true
Creating blank nodes
With a given blank node label:
const term: RDF.BlankNode = factory.blankNode('bnode');
console.log(term.value); // 'bnode'
console.log(term.termType); // 'BlankNode'
console.log(term.equals(term)); // true
Autogenerate a blank node label using an internal blank node counter:
const term: RDF.BlankNode = factory.blankNode();
console.log(term.value); // 'df-0'
console.log(term.termType); // 'BlankNode'
console.log(term.equals(term)); // true
Reset the blank node label counter:
factory.resetBlankNodeCounter();
Creating literals
Plain string literal:
const term: RDF.Literal = factory.literal('abc');
console.log(term.value); // 'abc'
console.log(term.termType); // 'Literal'
console.log(term.language); // ''
console.log(term.datatype); // namedNode('http://www.w3.org/2001/XMLSchema#string')
console.log(term.equals(term)); // true
Languaged tagged string literal:
const term: RDF.Literal = factory.literal('abc', 'en-us');
console.log(term.value); // 'abc'
console.log(term.termType); // 'Literal'
console.log(term.language); // 'en-us'
console.log(term.datatype); // namedNode('http://www.w3.org/1999/02/22-rdf-syntax-ns#langString')
console.log(term.equals(term)); // true
Datatyped literal:
const term: RDF.Literal = factory.literal('1.2', factory.namedNode('http://www.w3.org/2001/XMLSchema#double'));
console.log(term.value); // 'abc'
console.log(term.termType); // 'Literal'
console.log(term.language); // ''
console.log(term.datatype); // namedNode('http://www.w3.org/2001/XMLSchema#double')
console.log(term.equals(term)); // true
Creating variables
const term: RDF.Variable = factory.variable('myVar');
console.log(term.value); // 'myVar'
console.log(term.termType); // 'Variable'
console.log(term.equals(term)); // true
Getting the default graph
This will always produce the same default graph instance;
const term: RDF.DefaultGraph = factory.defaultGraph();
console.log(term.value); // ''
console.log(term.termType); // 'DefaultGraph'
console.log(term.equals(term)); // true
Creating quads
Create a triple in the default graph:
const quad: RDF.Quad = factory.quad(
factory.namedNode('ex:s'),
factory.namedNode('ex:p'),
factory.literal('o'),
);
console.log(term.subject); // An RDF.Term
console.log(term.predicate); // An RDF.Term
console.log(term.object); // An RDF.Term
console.log(term.graph); // An RDF.Term, in this case defaultGraph()
console.log(quad.equals(quad)); // true
Create a triple in a named graph:
const quad: RDF.Quad = factory.quad(
factory.namedNode('ex:s'),
factory.namedNode('ex:p'),
factory.literal('o'),
factory.namedNode('ex:g'),
);
console.log(term.subject); // An RDF.Term
console.log(term.predicate); // An RDF.Term
console.log(term.object); // An RDF.Term
console.log(term.graph); // An RDF.Term
console.log(quad.equals(quad)); // true
Since a Quad
is also a Term
, it is possible to annotate Quad
's by nesting them:
const quad: RDF.Quad = factory.quad(
factory.quad(
factory.namedNode('ex:s'),
factory.namedNode('ex:p1'),
factory.literal('o'),
),
factory.namedNode('ex:p2'),
factory.literal('o'),
);
Copying terms
Create a deep copy of the given term:
const term1 = factory.namedNode('ex:s');
const term1 = factory.fromTerm(term1);
This is useful if you need to transform terms from another data factory.
Copying quads
Create a deep copy of the given quad:
const quad1: RDF.Quad = factory.quad(
factory.namedNode('ex:s'),
factory.namedNode('ex:p'),
factory.literal('o'),
);
const quad2 = factory.fromQuad(quad1);
This is useful if you need to transform quads from another data factory.
Nested quads will be copied recursively to produce an actual deep copy.
License
This software is written by Ruben Taelman.
This code is released under the MIT license.