@comunica/mediator-combine-union

Comunica Mediator Combine Union

A comunica mediator that takes the union of all actor results.

This module is part of the Comunica framework, and should only be used by developers that want to build their own query engine.

Click here if you just want to query with Comunica.

Install

$ yarn add @comunica/mediator-combine-union

Configure

After installing, this mediator can be instantiated as follows:

{
  "@context": [
    ...
    "https://linkedsoftwaredependencies.org/bundles/npm/@comunica/mediator-combine-union/^4.0.0/components/context.jsonld"
  ],
  "actors": [
    ...
    {
      "@type": "SomeActor",
      "someMediator": {
        "@id": "#mediatorRdfParseMediatypes",
        "@type": "MediatorCombineUnion",
        "bus": { "@id": "ActorRdfParse:_default_bus" },
        "field": "mediaTypes"
      }
    }
  ]
}

Config Parameters

• bus: Identifier of the bus to mediate over.
• field: The field name to mediate over.
• filterErrors: Optional flag to indicate if actors that throw test errors should be filtered out of the pipeline, defaults to false.

Changelog

v4.4.0 - 2025-09-17

Added

• Accept RDF/JS datasets as sources
• Include VoID metadata in SPARQL endpoint, Closes #1545
• Add automatic type casting for xs:untypedAtomic
• Vary requests to SPARQL endpoints using Accept-Post header
• Allow fileBaseIRI to be set, Closes #1540
• Send extension functions to remote SPARQL endpoints if supported.
  • Only push down extension functions to sources if allowed
  • List and detect extension functions in service descriptions

Changed

• Make sources field type in context less strict, Closes #1615
• Make partial cardinality emission optional (#1618)
• Cache identified sources in service operation actor
• Send short SPARQL endpoint requests as GET
• Update to immutable v5
• Optimizations:
  • Optimize OPTIONALs with expressions applying to only left or right
  • Avoid cartesian products in actor-rdf-join-inner-multi-smallest

Fixed

• Fix wrong handling of FILTER in OPTIONAL
• Fix distinctConstruct not working when over a single SPARQL endpoint
• Skip ActorIteratorTransformRecordIntermediateResults if context entry is missing
• Fix incorrect context being used during empty source pruning
• Use ASK to verify cardinality estimate-based source assignments (#1587)

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