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• Source attribution

Source attribution

Comunica can track the sources that contribute to query results, which corresponds to where-provenance. However, this feature is not enabled by default due to the overhead of computing source attributions. Enabling it requires a custom configuration.

To achieve this, Comunica wraps all query sources in a QuerySourceAddSourceAttribution via ActorQuerySourceIdentifyHypermediaAnnotateSource. This actor sets the URL of each query source in the context of the bindings it produces.

During joins, the contexts of these bindings are merged using the SetUnionBindingsContextMergeHandler, which is constructed by ActorMergeBindingsContextUnion.

Serializing Source Attribution

When using Comunica via the command line, only the result bindings are shown by default, and the binding context is discarded.

To include source attribution in the output, you can use ActorQueryProcessAnnotateSourceBinding, which binds computed attributions to the _source key.

Configuration

First add the following actors to the Comunica configuration:

{
    "@context": [
        "https://linkedsoftwaredependencies.org/bundles/npm/@comunica/runner/^4.0.0/components/context.jsonld",
        "https://linkedsoftwaredependencies.org/bundles/npm/@comunica/actor-query-source-identify-hypermedia-annotate-source/^4.0.0/components/context.jsonld"    
    ],
    "@id": "urn:comunica:default:Runner",
    "@type": "Runner",
    "actors": [ 
        {
            "@id": "urn:comunica:default:query-source-identify-hypermedia/actors#annotate-source",
            "@type": "ActorQuerySourceIdentifyHypermediaAnnotateSource",
            "mediatorMergeBindingsContext": { "@id": "urn:comunica:default:merge-bindings-context/mediators#main" },
            "mediatorQuerySourceIdentifyHypermedia": { "@id": "urn:comunica:default:query-source-identify-hypermedia/mediators#main" },
            "beforeActors": [
                { "@id": "urn:comunica:default:query-source-identify-hypermedia/actors#none" },
                { "@id": "urn:comunica:default:rdf-resolve-quad-pattern/actors#sparql" },
                { "@id": "urn:comunica:default:query-source-identify-hypermedia/actors#qpf" }
            ]
        }
    ]
}

ActorMergeBindingsContextUnion:

{
  "@context": [
    "https://linkedsoftwaredependencies.org/bundles/npm/@comunica/runner/^4.0.0/components/context.jsonld",
    "https://linkedsoftwaredependencies.org/bundles/npm/@comunica/actor-merge-bindings-context-union/^4.0.0/components/context.jsonld"
  ],
  "@id": "urn:comunica:default:Runner",
  "@type": "Runner",
  "actors": [
    {
      "@id": "urn:comunica:default:merge-bindings-context/actors#source-binding-union",
      "@type": "ActorMergeBindingsContextUnion",
      "contextKey": "@comunica/bus-merge-bindings-context:sourcesBinding"
    }
  ]
}

ActorQueryProcessAnnotateSourceBinding (Optional):

{
  "@context": [
    "https://linkedsoftwaredependencies.org/bundles/npm/@comunica/runner/^4.0.0/components/context.jsonld",
    "https://linkedsoftwaredependencies.org/bundles/npm/@comunica/actor-query-process-annotate-source-binding/^4.0.0/components/context.jsonld"
  ],
  "@id": "urn:comunica:default:Runner",
  "@type": "Runner",
  "actors": [
    {
      "@id": "urn:comunica:default:query-process/actors#annotate-source-binding",
      "@type": "ActorQueryProcessAnnotateSourceBinding",
      "mediatorQueryProcess": { "@id": "urn:comunica:default:query-process/mediators#main" },
      "beforeActors": [
        { "@id": "urn:comunica:default:query-process/actors#sequential" }
      ]
    }
  ]
}

Expected Output

With this configuration, running the following query:

node engines/query-sparql/bin/query.js https://ruben.verborgh.org/profile/ https://www.rubensworks.net/publications/ -q "PREFIX schema: <http://schema.org/>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
SELECT *
WHERE {
  ?article a schema:ScholarlyArticle;
     foaf:maker|schema:author ?author;
           foaf:name|schema:name ?name.
}"

will produce:

{"article":"_:bc_1_df_11_4","author":"https://www.linkedin.com/in/bryanelliotttam/","name":"\"Optimizing Traversal Queries of Sensor Data Using a Rule-Based Reachability Approach\"","_source":"\"[\"https://www.rubensworks.net/publications/\"]\""},
{"article":"_:bc_1_df_11_4","author":"https://www.rubensworks.net/","name":"\"Optimizing Traversal Queries of Sensor Data Using a Rule-Based Reachability Approach\"","_source":"\"[\"https://www.rubensworks.net/publications/\"]\""},
...