# Comunica SPARQL Query Source Identify Hypermedia Actor

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A [Query Source Identify Hypermedia](https://github.com/comunica/comunica/tree/master/packages/bus-query-source-identify-hypermedia) actor that handles [SPARQL endpoints](https://www.w3.org/TR/sparql11-protocol/).

This module is part of the [Comunica framework](https://github.com/comunica/comunica),
and should only be used by [developers that want to build their own query engine](https://comunica.dev/docs/modify/).

[Click here if you just want to query with Comunica](https://comunica.dev/docs/query/).

## Install

```bash
$ yarn add @comunica/actor-query-source-identify-hypermedia-sparql
```

## Configure

After installing, this package can be added to your engine's configuration as follows:
```text
{
  "@context": [
    ...
    "https://linkedsoftwaredependencies.org/bundles/npm/@comunica/actor-query-source-identify-hypermedia-sparql/^1.0.0/components/context.jsonld"
  ],
  "actors": [
    ...
    {
      "@id": "urn:comunica:default:query-source-identify-hypermedia/actors#sparql",
      "@type": "ActorQuerySourceIdentifyHypermediaSparql",
      "mediatorHttp": { "@id": "urn:comunica:default:http/mediators#main" },
      "mediatorMergeBindingsContext": { "@id": "urn:comunica:default:merge-bindings-context/mediators#main" },
      "mediatorQuerySerialize": { "@id": "urn:comunica:default:query-serialize/mediators#main" },
      "sparqlServerSoftwarePatterns": ["Virtuoso", "Fuseki"]
    }
  ]
}
```

### Config Parameters

* `mediatorHttp`: A mediator over the [HTTP bus](https://github.com/comunica/comunica/tree/master/packages/bus-http).
* `mediatorMergeBindingsContext`: A mediator over the [Merge Bindings Context bus](https://github.com/comunica/comunica/tree/master/packages/bus-merge-bindings-context).
* `mediatorQuerySerialize`: A mediator over the [Query Serialize bus](https://github.com/comunica/comunica/tree/master/packages/bus-query-serialize).
* `checkUrlSuffix`: If URLs ending with '/sparql' should also be considered SPARQL endpoints, defaults to `true`.
* `forceHttpGet`: If queries should be sent via HTTP GET instead of POST, defaults to `false`.
* `forceSourceType`: Forces all sources provided to be interpreted as SPARQL endpoints, defaults to `false`.
* `cacheSize`: The cache size for COUNT queries, defaults to `1024`.
* `bindMethod`: The query operation for communicating bindings, defaults to `'values'`, alt: `'union'` or `'filter'`.
* `countTimeout`: Timeout in ms of how long count queries are allowed to take. If the timeout is reached, an infinity cardinality is returned. Defaults to `3000`.
* `cardinalityCountQueries`: If count queries should be sent to obtain the cardinality of (sub)queries. If set to false, resulting cardinalities will always be considered infinity. Defaults to `true`
* `cardinalityEstimateConstruction`: If cardinality estimates for larger queries should be constructed locally from (sub)query cardinalities when possible. Defaults to `false`. If set to false, count queries will be sent for every operation at all levels.
* `sparqlServerSoftwarePatterns`: An optional list of regular expressions to match against the `Server` HTTP response header. If a match is found, the source is identified as a SPARQL endpoint.

## Endpoint Server Header Report

The following endpoints have been observed to return the following `Server` headers (at the time of writing):

| Endpoint                                                          | Server Header                                                          |
| ----------------------------------------------------------------- | ---------------------------------------------------------------------- |
| http://lod.sztaki.hu/sparql                                       | `Virtuoso/06.01.3127 (Linux) i686-pc-linux-gnu`                        |
| http://linguistic.linkeddata.es/sparql                            | `Virtuoso/06.01.3127 (Linux) x86_64-pc-linux-gnu`                      |
| http://www.genome.jp/sparql/linkdb                                | `Virtuoso/07.20.3217 (Linux) x86_64-unknown-linux-gnu`                 |
| http://sparql.archives-ouvertes.fr/sparql                         | `Virtuoso/07.20.3229 (Linux) x86_64-pc-linux-gnu`                      |
| http://data.persee.fr/sparql                                      | `Virtuoso/07.20.3230 (Linux) x86_64-generic_glibc25-linux-gnu`         |
| http://linkedgeodata.org/sparql                                   | `Virtuoso/07.20.3233 (Linux) x86_64-pc-linux-gnu`                      |
| http://kaiko.getalp.org/sparql                                    | `Virtuoso/07.20.3240 (Linux) x86_64-pc-linux-gnu`                      |
| http://data.cervantesvirtual.com/openrdf-sesame/repositories/data | `Virtuoso/07.20.3240 (Linux) x86_64-pc-linux-gnu`                      |
| http://sparql.hegroup.org/sparql/                                 | `Virtuoso/07.20.3241 (Linux) x86_64-pc-linux-gnu`                      |
| http://dbpedia.org/sparql                                         | `Virtuoso/08.03.3334 (Linux) x86_64-ubuntu_noble-linux-glibc2.39  VDB` |
| https://lov.linkeddata.es/dataset/lov/sparql                      | `Fuseki (1.1.1)`                                                       |
| http://lov.okfn.org/endpoint/lov                                  | `Fuseki (1.1.1)`                                                       |