rdf-data-factory

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.