The N3.js library is an implementation of the RDF.js low-level specification that lets you handle RDF in JavaScript easily. It offers:
- Parsing triples/quads from Turtle, TriG, N-Triples, N-Quads, RDF* and Notation3 (N3)
- Writing triples/quads to Turtle, TriG, N-Triples, N-Quads and RDF*
- Storage of triples/quads in memory
Parsing and writing is:
- 🎛 asynchronous – triples arrive as soon as possible
- 🚰 streaming – streams are parsed as data comes in, so you can parse files larger than memory
- ⚡️ fast – triples are flying out at high speeds
For Node.js, N3.js comes as an npm package.
$ npm install n3const N3 = require('n3');N3.js seamlessly works in browsers via webpack
or browserify.
If you're unfamiliar with these tools,
you can read
webpack: Creating a Bundle – getting started
or
Introduction to browserify.
You will need to create a "UMD bundle" and supply a name (e.g. with the -s N3 option in browserify).
You can also load it via CDN:
<script src="https://unpkg.com/n3/browser/n3.min.js"></script>N3.js follows the RDF.js low-level specification.
N3.DataFactory will give you the factory functions to create triples and quads:
const { DataFactory } = N3;
const { namedNode, literal, defaultGraph, quad } = DataFactory;
const myQuad = quad(
namedNode('https://ruben.verborgh.org/profile/#me'),
namedNode('http://xmlns.com/foaf/0.1/givenName'),
literal('Ruben', 'en'),
defaultGraph(),
);
console.log(myQuad.termType); // Quad
console.log(myQuad.value); // ''
console.log(myQuad.subject.value); // https://ruben.verborgh.org/profile/#me
console.log(myQuad.object.value); // Ruben
console.log(myQuad.object.datatype.value); // http://www.w3.org/1999/02/22-rdf-syntax-ns#langString
console.log(myQuad.object.language); // enIn the rest of this document, we will treat “triples” and “quads” equally: we assume that a quad is simply a triple in a named or default graph.
N3.Parser transforms Turtle, TriG, N-Triples, or N-Quads document into quads through a callback:
const parser = new N3.Parser();
parser.parse(
`PREFIX c: <http://example.org/cartoons#>
c:Tom a c:Cat.
c:Jerry a c:Mouse;
c:smarterThan c:Tom.`,
(error, quad, prefixes) => {
if (quad)
console.log(quad);
else
console.log("# That's all, folks!", prefixes);
});The callback's first argument is an optional error value, the second is a quad.
If there are no more quads,
the callback is invoked one last time with null for quad
and a hash of prefixes as third argument.
Pass a second callback to parse to retrieve prefixes as they are read.
If no callbacks are provided, parsing happens synchronously.
By default, N3.Parser parses a permissive superset of Turtle, TriG, N-Triples, and N-Quads.
For strict compatibility with any of those languages, pass a format argument upon creation:
const parser1 = new N3.Parser({ format: 'N-Triples' });
const parser2 = new N3.Parser({ format: 'application/trig' });Notation3 (N3) is supported only through the format argument:
const parser3 = new N3.Parser({ format: 'N3' });
const parser4 = new N3.Parser({ format: 'Notation3' });
const parser5 = new N3.Parser({ format: 'text/n3' });It is possible to provide the base IRI of the document that you want to parse.
This is done by passing a baseIRI argument upon creation:
const parser = new N3.Parser({ baseIRI: 'http://example.org/' });By default, N3.Parser will prefix blank node labels with a b{digit}_ prefix.
This is done to prevent collisions of unrelated blank nodes having identical
labels. The blankNodePrefix constructor argument can be used to modify the
prefix or, if set to an empty string, completely disable prefixing:
const parser = new N3.Parser({ blankNodePrefix: '' });N3.Parser can parse Node.js streams as they grow,
returning quads as soon as they're ready.
const parser = new N3.Parser(),
rdfStream = fs.createReadStream('cartoons.ttl');
parser.parse(rdfStream, console.log);N3.StreamParser is a Node.js stream and RDF.js Sink implementation.
This solution is ideal if your consumer is slower,
since source data is only read when the consumer is ready.
const streamParser = new N3.StreamParser(),
rdfStream = fs.createReadStream('cartoons.ttl');
rdfStream.pipe(streamParser);
streamParser.pipe(new SlowConsumer());
function SlowConsumer() {
const writer = new require('stream').Writable({ objectMode: true });
writer._write = (quad, encoding, done) => {
console.log(quad);
setTimeout(done, 1000);
};
return writer;
}A dedicated prefix event signals every prefix with prefix and term arguments.
N3.Writer serializes quads as an RDF document.
Write quads through addQuad.
const writer = new N3.Writer({ prefixes: { c: 'http://example.org/cartoons#' } });
writer.addQuad(
namedNode('http://example.org/cartoons#Tom'),
namedNode('http://www.w3.org/1999/02/22-rdf-syntax-ns#type'),
namedNode('http://example.org/cartoons#Cat')
);
writer.addQuad(quad(
namedNode('http://example.org/cartoons#Tom'),
namedNode('http://example.org/cartoons#name'),
literal('Tom')
));
writer.end((error, result) => console.log(result));By default, N3.Writer writes Turtle (or TriG if some quads are in a named graph).
To write N-Triples (or N-Quads) instead, pass a format argument upon creation:
const writer1 = new N3.Writer({ format: 'N-Triples' });
const writer2 = new N3.Writer({ format: 'application/trig' });N3.Writer can also write quads to a Node.js stream.
const writer = new N3.Writer(process.stdout, { end: false, prefixes: { c: 'http://example.org/cartoons#' } });
writer.addQuad(
namedNode('http://example.org/cartoons#Tom'),
namedNode('http://www.w3.org/1999/02/22-rdf-syntax-ns#type'),
namedNode('http://example.org/cartoons#Cat')
);
writer.addQuad(quad(
namedNode('http://example.org/cartoons#Tom'),
namedNode('http://example.org/cartoons#name'),
literal('Tom')
));
writer.end();N3.StreamWriter is a Node.js stream and RDF.js Sink implementation.
const streamParser = new N3.StreamParser(),
inputStream = fs.createReadStream('cartoons.ttl'),
streamWriter = new N3.StreamWriter({ prefixes: { c: 'http://example.org/cartoons#' } });
inputStream.pipe(streamParser);
streamParser.pipe(streamWriter);
streamWriter.pipe(process.stdout);You might want to use the […] and list (…) notations of Turtle and TriG.
However, a streaming writer cannot create these automatically:
the shorthand notations are only possible if blank nodes or list heads are not used later on,
which can only be determined conclusively at the end of the stream.
The blank and list functions allow you to create them manually instead:
const writer = new N3.Writer({ prefixes: { c: 'http://example.org/cartoons#',
foaf: 'http://xmlns.com/foaf/0.1/' } });
writer.addQuad(
writer.blank(
namedNode('http://xmlns.com/foaf/0.1/givenName'),
literal('Tom', 'en')),
namedNode('http://www.w3.org/1999/02/22-rdf-syntax-ns#type'),
namedNode('http://example.org/cartoons#Cat')
);
writer.addQuad(quad(
namedNode('http://example.org/cartoons#Jerry'),
namedNode('http://xmlns.com/foaf/0.1/knows'),
writer.blank([{
predicate: namedNode('http://www.w3.org/1999/02/22-rdf-syntax-ns#type'),
object: namedNode('http://example.org/cartoons#Cat'),
},{
predicate: namedNode('http://xmlns.com/foaf/0.1/givenName'),
object: literal('Tom', 'en'),
}])
));
writer.addQuad(
namedNode('http://example.org/cartoons#Mammy'),
namedNode('http://example.org/cartoons#hasPets'),
writer.list([
namedNode('http://example.org/cartoons#Tom'),
namedNode('http://example.org/cartoons#Jerry'),
])
);
writer.end((error, result) => console.log(result));N3.Store allows you to store triples in memory and find them fast.
In this example, we create a new store and add the triples :Pluto a :Dog. and :Mickey a :Mouse.
Then, we find triples with :Mickey as subject.
const store = new N3.Store();
store.add(
namedNode('http://ex.org/Pluto'),
namedNode('http://ex.org/type'),
namedNode('http://ex.org/Dog')
);
store.add(
namedNode('http://ex.org/Mickey'),
namedNode('http://ex.org/type'),
namedNode('http://ex.org/Mouse')
);
// Retrieve all quads
for (const quad of store)
console.log(quad);
// Retrieve Mickey's quads
for (const quad of store.match(namedNode('http://ex.org/Mickey'), null, null))
console.log(quad);This store adheres to the DatasetCore interface which exposes the following properties
Attributes:
size— A non-negative integer that specifies the number of quads in the set.
Methods:
add— Adds the specified quad to the dataset. Existing quads, as defined inQuad.equals, will be ignored.delete— Removes the specified quad from the dataset.has— Determines whether a dataset includes a certain quad.match— Returns a new dataset that is comprised of all quads in the current instance matching the given arguments.[Symbol.iterator]— Implements the iterator protocol to allow iteration over allquadsin the dataset as in the example above.
The store provides the following manipulation methods in addition to implementing the standard DatasetCore Interface
(documentation):
addQuadto insert one quadaddQuadsto insert an array of quadsremoveQuadto remove one quadremoveQuadsto remove an array of quadsremoveto remove a stream of quadsremoveMatchesto remove all quads matching the given patterndeleteGraphto remove all quads with the given graphcreateBlankNodereturns an unused blank node identifier
The store provides the following search methods (documentation):
readQuadsreturns a generator of quads matching the given patterngetQuadsreturns an array of quads matching the given patternmatchreturns a stream of quads matching the given patterncountQuadscounts the number of quads matching the given patternforEachexecutes a callback on all matching quadseveryreturns whether a callback on matching quads always returns truesomereturns whether a callback on matching quads returns true at least oncegetSubjectsreturns an array of unique subjects occurring in matching quadsforSubjectsexecutes a callback on unique subjects occurring in matching quadsgetPredicatesreturns an array of unique predicates occurring in matching quadforPredicatesexecutes a callback on unique predicates occurring in matching quadsgetObjectsreturns an array of unique objects occurring in matching quadforObjectsexecutes a callback on unique objects occurring in matching quadsgetGraphsreturns an array of unique graphs occurring in matching quadforGraphsexecutes a callback on unique graphs occurring in matching quads
The N3.js parser and writer is fully compatible with the following W3C specifications:
- RDF 1.1 Turtle – EARL report
- RDF 1.1 TriG – EARL report
- RDF 1.1 N-Triples – EARL report
- RDF 1.1 N-Quads – EARL report
In addition, the N3.js parser also supports Notation3 (N3) (no official specification yet).
The N3.js parser and writer are also fully compatible with the RDF* variants of the W3C specifications.
The default mode is permissive
and allows a mixture of different syntaxes, including RDF*.
Pass a format option to the constructor with the name or MIME type of a format
for strict, fault-intolerant behavior.
If a format string contains star or *
(e.g., turtlestar or TriG*),
RDF* support for that format will be enabled.
The N3.js submodules are compatible with the following RDF.js interfaces:
N3.DataFactoryimplementsDataFactoryN3.StreamParserimplementsStreamandSinkN3.StreamWriterimplementsStreamandSinkN3.StoreimplementsStoreSourceSinkDatasetCore
The N3.js library is copyrighted by Ruben Verborgh and released under the MIT License.
Contributions are welcome, and bug reports or pull requests are always helpful. If you plan to implement a larger feature, it's best to contact me first.