
Can't find an answer to your question?
Feel free to [ask us](/ask/), or have a look at the
[example](https://github.com/comunica/examples) repository.

## Should I publish my package to npm before I can use it?

While it is recommended to publish your reusable Comunica packages to npm, this is not required.
The [Components.js](/docs/modify/advanced/componentsjs/) dependency injection framework is able to work with packages that are locally linked to each other, as long as they are available in the `node_modules/` directory.

If you receive warnings in the form of `Detected remote context lookup for...`,
this usually means that Components.js was not able to find the corresponding package locally, and will [fallback to a remote context lookup](https://github.com/LinkedSoftwareDependencies/Components.js/discussions/82).
This can either be caused by an incorrect context URL, or a missing dependency in the `node_modules/` directory.

## How to query over a non-RDF source?

Adding support for new types of sources is typically done by adding a new actor to
the [RDF Resolve Quad Pattern bus](/docs/modify/advanced/buses/#rdf-resolve-quad-pattern).
[Click here](https://github.com/comunica/examples/tree/master/packages/actor-rdf-resolve-quad-pattern-api-weather)
to find an example on how to query over a JSON weather API source.

## How to count all triples that are received by the query engine?

[Click here](https://github.com/comunica/examples/tree/master/packages/actor-observe-rdf-dereference)
to find an example on how this can be done.


Frequently asked question about Comunica modification.

Modify FAQ

About

Organization for ensuring the maintenance and development of the Comunica

Comunica Association

The board makes decisions regarding the Comunica Association

Board of Directors

The process for handling bounties on issues

Bounty Procedures

Blog posts, containing announcements or other news.

Blog

A New Website for Comunica

Release 1.16.0: Full spec compliance, property paths, CSV/TSV, basic auth, and fixes

Hacktoberfest and Release 1.17.0

Release 1.18.0: Smaller Web bundles and Microdata parsing

Release 1.19.0: Simplifications for extensions

Release 1.20.0: SPARQL Update support

Release 1.21.0: Hypermedia-based SPARQL Updating

Announcing the Comunica Association, and a Bounty Program

Release 1.22.0: Improved update support, extension functions, and improved CLI handling

Comunica Association Memberships

Release 2.0.0: A new major release with radical simplifications and performance improvements

Release 2.3.0: Better timeout support and minor enhancements

Official launch of the Comunica Association

Release 2.4.0: Better browser support and performance improvements

Release 2.5.0: Fixes, string sources, and HTTP error handling

Release 2.7.0: Better date support, better performance over SPARQL endpoints, and internal fixes

Release 2.8.0: Support for quoted triples (RDF-star and SPARQL-star)

Release 3.0: 🔥 Blazingly fast federation over heterogeneous sources

Release 3.1: 🌱 New package with tiny bundle size

Release 3.2: 🔎 Knowing what to optimize

Release 4.0: 🚄 Faster actor testing and modularized expressions

Contribute to the development of Comunica.

Contribute

Documentation

Learn how to configure your own Comunica engine, or extend Comunica by implementing new components.

Modify Comunica

Advanced guides on how to get the most out of Comunica modification.

Advanced modification

Overview of common design patterns for actors

Actor Patterns

The internal representation of queries during query execution.

Algebra

The low-level software architecture of Comunica for achieving modularity.

Core Architecture

The high-level software architecture of Comunica for implementing SPARQL.

SPARQL Architecture

All modules in Comunica can be built for the browser.

Browser builds

An overview of all buses in Comunica and their actors.

Buses and Actors

Components.js is the dependency injection framework that Comunica uses to wire components via config files.

Components.js

Custom CLI arguments

The expression evaluation engine of Comunica.

Expression Evaluator

Discovery of data source capabilities during query execution.

Hypermedia

Overview of how join operations are handled during query planning

Joins

Guide on how to use a local development version of Comunica with another local project

Linking local Comunica versions to other projects

Logging

An overview of all mediators in Comunica.

Mediators

Information for adaptive planning of query operations.

Metadata

Passively observe actions executed by actors on a given bus.

Observers

An overview of the different output types for query operations.

Query operation result types

Basic concepts behind parsing and serializing RDF.

RDF Parsing and Serializing

The unit and integration tests that lead to a more stable codebase.

Testing

Guidelines on running experiments with Comunica.

Benchmarking

Extensions

Basic guides on how to easily get started with Comunica modification.

Getting started with modification

For an existing actor, add a parameter that can be customized in the config file.

Adding a config parameter to an actor

Setup a development environment, implement a new actor, and create a pull request.

Contributing a new query operation actor to the Comunica repository

Create a custom configuration of Comunica modules with changed features, and query with it from within your application using the JavaScript API.

Querying with a custom configuration in a JavaScript app

Create a custom configuration of Comunica modules with reduced features, and query with it from the command line.

Querying with a custom configuration from the command line

Wrap your config in an npm package, and expose a CLI tool and a JavaScript API.

Exposing your custom config as an npm package

Demonstrate your query engine as a static Web page.

Exposing your custom config in a Web client

Learn how to execute queries in different environments. Such as live in the browser, in JavaScript applications, or the CLI.

Query with Comunica

Advanced guides on how to get the most out of Comunica.

Advanced querying

Send authenticated HTTP requests by including username and password.

HTTP Basic Authentication

Bindings objects are used to represent results of SPARQL SELECT queries

Bindings

When remote sources are requested, caching allows them to be reused in the future.

Caching

A context can be passed to a query engine to tweak its runtime settings.

Passing a context

Comunica detects and handles different types of destinations.

Destination types

Display information about the logical and physical query plan

Explain

Providing implementations for SPARQL extension functions.

Extension Functions

Query over the union of data within any number of sources

Federated Querying

Using the power of JSON-LD contexts, GraphQL queries can be executed by Comunica

GraphQL-LD

HDT offers highly compressed immutable RDF storage.

Loggers can be set to different logging levels to inspect what Comunica is doing behind the scenes.

Using the Memento protocol, time travel queries can be executed.

Memento

All HTTP requests can optionally go through a proxy.

HTTP Proxy

To achieve maximum interoperability between different JavaScript libraries, Comunica builds on top of the RDF/JS specifications.

RDF/JS

If the built-in source types are not sufficient, you can pass a custom JavaScript object implementing a specific interface.

Querying over RDF/JS sources

If the built-in destination types are not sufficient, you can pass a custom JavaScript object implementing a specific interface.

Updating RDF/JS stores

Query results can be serialized in different formats.

Result formats

Solid – the Web-based decentralization ecosystem – can be queried with Comunica.

Solid

Comunica detects and handles different types of sources.

Source types

Different SPARQL query types are possible, such as SELECT, CONSTRUCT, ASK, ...

SPARQL query types

Comunica supports several RDF-related specifications

Supported specifications

Frequently asked questions about using Comunica.

Querying FAQ

Basic guides on how to easily get started with querying.

Getting started with querying

Execute SPARQL queries from within your application using the JavaScript API.

Querying in a JavaScript app

Execute SPARQL queries from within your client-side browser application using the JavaScript API.

Querying in a JavaScript browser app

Execute SPARQL queries directly from the command line.

Querying from the command line

Execute SPARQL queries over local RDF files directly from the command line.

Querying local files from the command line

If you want to make use of the latest changes that are not released yet

Query using the latest development version

Execute SPARQL queries within a Docker container.

Querying from a Docker container

Allow querying over HTTP via the SPARQL protocol

Setting up a SPARQL endpoint

Set up a user-friendly static Web page where SPARQL queries can be executed client-side

Setting up a Web client

Execute SPARQL Update queries from within your application using the JavaScript API.

Updating in a JavaScript app

Execute SPARQL Update queries directly from the command line.

Updating from the command line

Usage showcase

Events

Comunica tutorial at the ESWC 2019 conference

2019-06-03: Tutorial at ESWC 2019

Comunica and Solid tutorial at the ISWC 2019 conference

2019-10-26: Tutorial at ISWC 2019

An online event for the official launch of the Comunica Association

2022-09-07: Comunica Association Launch

The Comunica Association will have a booth and talk at the Semantics Conference in Vienna

2022-09-13/15: Semantics Conference

Logos

An overview of these research surrounding Comunica.

Research

An overview of research that has been done on AMFs during query execution.

Approximate Membership Functions

An overview of research that has been done on Link-Traversal-based Query Processing.

Link Traversal

An overview of research that has been done on Query Processing for RDF archives.