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-star and Notation3 (N3)
- Writing triples/quads to Turtle, TriG, N-Triples, N-Quads and RDF-star
- 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 n3
const 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'), // Subject
namedNode('http://xmlns.com/foaf/0.1/givenName'), // Predicate
literal('Ruben', 'en'), // Object
defaultGraph(), // Graph
);
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); // en
In 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 add
.
const writer = new N3.Writer({ prefixes: { c: 'http://example.org/cartoons#' } }); // Create a writer which uses `c` as a prefix for the namespace `http://example.org/cartoons#`
writer.add(quad(
namedNode('http://example.org/cartoons#Tom'), // Subject
namedNode('http://example.org/cartoons#name'), // Predicate
literal('Tom') // Object
));
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 through addQuad
.
const writer = new N3.Writer(process.stdout, { end: false, prefixes: { c: 'http://example.org/cartoons#' } });
writer.addQuad(
namedNode('http://example.org/cartoons#Tom'), // Subject
namedNode('http://www.w3.org/1999/02/22-rdf-syntax-ns#type'), // Predicate
namedNode('http://example.org/cartoons#Cat') // Object
);
writer.addQuad(quad(
namedNode('http://example.org/cartoons#Tom'), // Subject
namedNode('http://example.org/cartoons#name'), // Predicate
literal('Tom') // Object
));
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(
quad(
namedNode('http://ex.org/Pluto'),
namedNode('http://ex.org/type'),
namedNode('http://ex.org/Dog')
)
);
store.add(
quad(
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);
If you are using multiple stores, you can reduce memory consumption by allowing them to share an entity index:
const entityIndex = new N3.EntityIndex();
const store1 = new N3.Store([], { entityIndex });
const store2 = new N3.Store([], { entityIndex });
This store adheres to the Dataset
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 allquads
in the dataset as in the example above.
The store implements the following manipulation methods in addition to the standard Dataset
Interface
(documentation):
addQuad
to insert one quadaddQuads
to insert an array of quadsremoveQuad
to remove one quadremoveQuads
to remove an array of quadsremove
to remove a stream of quadsremoveMatches
to remove all quads matching the given patterndeleteGraph
to remove all quads with the given graphcreateBlankNode
returns an unused blank node identifier
The store provides the following search methods (documentation):
match
returns a stream and generator of quads matching the given patterngetQuads
returns an array of quads matching the given patterncountQuads
counts the number of quads matching the given patternforEach
executes a callback on all matching quadsevery
returns whether a callback on matching quads always returns truesome
returns whether a callback on matching quads returns true at least oncegetSubjects
returns an array of unique subjects occurring in matching quadsforSubjects
executes a callback on unique subjects occurring in matching quadsgetPredicates
returns an array of unique predicates occurring in matching quadforPredicates
executes a callback on unique predicates occurring in matching quadsgetObjects
returns an array of unique objects occurring in matching quadforObjects
executes a callback on unique objects occurring in matching quadsgetGraphs
returns an array of unique graphs occurring in matching quadforGraphs
executes a callback on unique graphs occurring in matching quads
N3.js supports reasoning as follows:
import { Reasoner, Store, Parser } from 'n3';
const parser = new Parser({ format: 'text/n3' });
const rules = `
{
?s a ?o .
?o <http://www.w3.org/2000/01/rdf-schema#subClassOf> ?o2 .
} => {
?s a ?o2 .
} .
`
const rulesDataset = new Store(parser.parse(rules));
const dataset = new Store(/* Dataset */)
// Applies the rules to the store; mutating it
const reasoner = new Reasoner(store);
reasoner.reason(rules);
Note: N3.js currently only supports rules with Basic Graph Patterns in the premise and conclusion. Built-ins and backward-chaining are not supported. For an RDF/JS reasoner that supports all Notation3 reasoning features, see eye-js.
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-star variants of the W3C specifications.
The default mode is permissive
and allows a mixture of different syntaxes, including RDF-star.
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-star support for that format will be enabled.
The N3.js submodules are compatible with the following RDF.js interfaces:
N3.DataFactory
implementsDataFactory
N3.StreamParser
implementsStream
andSink
N3.StreamWriter
implementsStream
andSink
N3.Store
implementsStore
Source
Sink
DatasetCore
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.