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SPARQL Select query¤

The SPARQL SELECT plugin is a task for executing SPARQL SELECT queries on the input RDF data source.

Description¤

The sparqlSelectOperator plugin is an example of a RDF task or operator. Such a task can be used in a workflow, connecting an input to an output. In this specific case, the input is — in essence — a SPARQL endpoint and the output is the entity table containing the SPARQL results of the SPARQL SELECT query execution.

In general terms, a SPARQL 1.1 SELECT query is supported. One of the simplest examples is SELECT * WHERE { ?s ?p ?o }.

The result limit can be specified for the SPARQL SELECT plugin itself, with the parameter limit. Additionally, a timeout can be specified with the parameter sparqlTimeout.

As usual, the SPARQL results contain both “variables” and “bindings”, such as in this example. This tabular raw form is transformed into an entity table.

Internal Specifics¤

If the SPARQL source is defined on a specific graph, a FROM clause will be added to the query at execution time, except when there already exists a GRAPH or FROM clause in the query. FROM NAMED clauses are not injected.

Other types of RDF tasks are the sparqlCopyOperator for executing SPARQL CONSTRUCT queries, and the sparqlUpdateOperator for building SPARQL UPDATE queries from a templating engine.

Regarding the input dataset, any RDF dataset is acceptable. For further details on the RDF datasets, see for example the documentation of the sparqlEndpoint plugin.

Parameter¤

Select query¤

A SPARQL 1.1 select query

  • ID: selectQuery
  • Datatype: code-sparql
  • Default Value: None

Result limit¤

If set to a positive integer, the number of results is limited

  • ID: limit
  • Datatype: string
  • Default Value: None

Optional SPARQL dataset¤

An optional SPARQL dataset that can be used for example data, so e.g. the transformation editor shows mapping examples.

  • ID: optionalInputDataset
  • Datatype: SPARQL endpoint
  • Default Value: None

SPARQL query timeout (ms)¤

SPARQL query timeout (select/update) in milliseconds. A value of zero means that there is no timeout set explicitly. If a value greater zero is specified this overwrites possible default timeouts.

  • ID: sparqlTimeout
  • Datatype: int
  • Default Value: 0

Advanced Parameter¤

None

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