@comunica/query-sparql-file

Comunica SPARQL File

Comunica SPARQL is a SPARQL query engine for JavaScript for querying local and remote RDF files.

This module is part of the Comunica framework.

Install

$ yarn global add @comunica/query-sparql-file

or

$ npm install -g @comunica/query-sparql-file

Usage from the command line

Show 100 triples from a remote FOAF profile:

$ comunica-sparql-file https://ruben.verborgh.org/profile/#me "CONSTRUCT WHERE { ?s ?p ?o } LIMIT 100"

Show 100 triples from a local RDF file:

$ comunica-sparql-file path/to/my/file.ttl "CONSTRUCT WHERE { ?s ?p ?o } LIMIT 100"

Show all triples from a local and remote file:

$ comunica-sparql-file path/to/my/file.ttl https://ruben.verborgh.org/profile/#me "CONSTRUCT WHERE { ?s ?p ?o } LIMIT 100"

Show the help with all options:

$ comunica-sparql-file --help

Just like Comunica SPARQL, a dynamic variant (comunica-dynamic-sparql-file) also exists.

Read more about querying from the command line.

Usage within application

This engine can be used in JavaScript/TypeScript applications as follows:

const QueryEngine = require('@comunica/query-sparql-file').QueryEngine;
const myEngine = new QueryEngine();

const bindingsStream = await myEngine.queryBindings(`
  SELECT ?s ?p ?o WHERE {
    ?s ?p <http://dbpedia.org/resource/Belgium>.
    ?s ?p ?o
  } LIMIT 100`, {
  sources: ['http://fragments.dbpedia.org/2015/en'],
});

// Consume results as a stream (best performance)
bindingsStream.on('data', (binding) => {
    console.log(binding.toString()); // Quick way to print bindings for testing

    console.log(binding.has('s')); // Will be true

    // Obtaining values
    console.log(binding.get('s').value);
    console.log(binding.get('s').termType);
    console.log(binding.get('p').value);
    console.log(binding.get('o').value);
});
bindingsStream.on('end', () => {
    // The data-listener will not be called anymore once we get here.
});
bindingsStream.on('error', (error) => {
    console.error(error);
});

// Consume results as async iterable (easier)
for await (const binding of bindingsStream) {
  console.log(binding.toString());
}

// Consume results as an array (easier)
const bindings = await bindingsStream.toArray();
console.log(bindings[0].get('s').value);
console.log(bindings[0].get('s').termType);

Read more about querying an application.

Usage as a SPARQL endpoint

Start a webservice exposing http://fragments.dbpedia.org/2015-10/en via the SPARQL protocol, i.e., a SPARQL endpoint.

$ comunica-sparql-file-http path/to/my/file.ttl

Show the help with all options:

$ comunica-sparql-file-http --help

The SPARQL endpoint can only be started dynamically. An alternative config file can be passed via the COMUNICA_CONFIG environment variable.

Use bin/http.js when running in the Comunica monorepo development environment.

Read more about setting up a SPARQL endpoint.