Comunica SPARQL OSTRICH

Comunica SPARQL OSTRICH is a SPARQL query engine for JavaScript that enables versioned querying over OSTRICH archives.

This module is part of the Comunica framework.

Install

$ yarn add @comunica/query-sparql-ostrich

or

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

Install a prerelease

Since this package is still in testing phase, you may want to install a prerelease of this package, which you can do by appending @next to the package name during installation.

$ yarn add @comunica/query-sparql-ostrich@next

or

$ npm install -g @comunica/query-sparql-ostrich@next

Usage

Show 100 triples from an OSTRICH store at version 1:

$ comunica-sparql-ostrich [email protected] \
  "SELECT * WHERE {
    GRAPH <version:1> {
      ?s ?p ?o
    }
  } LIMIT 100"

Show the help with all options:

$ comunica-sparql-ostrich --help

Just like Comunica SPARQL, a dynamic variant (comunica-dynamic-sparql-ostrich) 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-ostrich').QueryEngine;
const myEngine = new QueryEngine();

const bindingsStream = await myEngine.queryBindings(`
  SELECT * WHERE {
    GRAPH <version:1> {
      ?s ?p ?o
    }
  } LIMIT 100`, {
    sources: [{ type: 'ostrichFile', value: 'dataset.ostrich' }],
    lenient: true,
});

// 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 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 an OSTRICH dataset via the SPARQL protocol, i.e., a SPARQL endpoint.

$ comunica-sparql-ostrich-http [email protected]

Show the help with all options:

$ comunica-sparql-ostrich-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.