LDflex is a domain-specific language for querying Linked Data on the Web as if you were browsing a local JavaScript graph.
You can write things like person.friends.firstName
to get a list of your friends.
Thanks to the power of JSON-LD contexts
and JavaScript's Proxy,
these properties are not hard-coded in LDflex,
but can be chosen at runtime.
They feel as if you're traversing a local object,
while you're actually querying the Web—without
pulling in all data first.
Tim Berners-Lee came up with the idea for such a fluid JavaScript interface to Linked Data, in a discussion on how to make Linked Data easier for developers.
npm install ldflex
In order to execute queries, you will also need a query engine:
npm install ldflex-comunica
When you have obtained a starting subject, you can navigate through its properties using standard JavaScript dot property syntax.
In order to query for the result,
use await
if you want a single value,
or for await
to iterate over all values.
const { PathFactory } = require('ldflex');
const { default: ComunicaEngine } = require('ldflex-comunica');
const { namedNode } = require('@rdfjs/data-model');
// The JSON-LD context for resolving properties
const context = {
"@context": {
"@vocab": "http://xmlns.com/foaf/0.1/",
"friends": "knows",
"label": "http://www.w3.org/2000/01/rdf-schema#label",
}
};
// The query engine and its source
const queryEngine = new ComunicaEngine('https://ruben.verborgh.org/profile/');
// The object that can create new paths
const path = new PathFactory({ context, queryEngine });
const ruben = path.create({ subject: namedNode('https://ruben.verborgh.org/profile/#me') });
showPerson(ruben);
async function showPerson(person) {
console.log(`This person is ${await person.name}`);
console.log(`${await person.givenName} is interested in:`);
for await (const name of person.interest.label)
console.log(`- ${name}`);
console.log(`${await person.givenName} is friends with:`);
for await (const name of person.friends.givenName)
console.log(`- ${name}`);
}
(async person => {
console.log(await person.friends.givenName.pathExpression);
})(ruben);
(async document => {
for await (const subject of document.subjects)
console.log(`${subject}`);
})(ruben);
(async subject => {
for await (const property of subject.properties)
console.log(`${property}`);
})(ruben);
(async person => {
console.log(await person.friends.givenName.sparql);
})(ruben);
©2018–present Ruben Verborgh, Ruben Taelman. MIT License.