Skip to content

SPARQL endpoint¤

The SPARQL endpoint plugin is a dataset for connecting to an existing, remote SPARQL endpoint.

Description¤

The sparqlEndpoint plugin is an example of a RDF dataset. A dataset is a collection of data to be read from or written into, both a source and a sink of information. A RDF dataset is a dataset that can deal with RDF data. There are several plugins for dealing with RDF datasets in the BUILD stage, depending on where the RDF dataset is located and how it is being accessed. In this case, the sparqlEndpoint dataset is a plugin that can access a remote SPARQL endpoint such as one of those listed by the W3C, e.g. Wikidata or DBpedia.

The SPARQL dataset (this plugin) is an instance of a RDF dataset. All RDF datasets provide the abstraction and functionality of a SPARQL endpoint. The SPARQL endpoint used in this plugin is a remote SPARQL endpoint. It can handle and execute SPARQL SELECT, ASK and CONSTRUCT queries. Additionally, it can execute updates.

Example usage¤

A very simple example showcasing the usage of this plugin is the following idea: Use an online SPARQL Query Editor such as https://dbpedia.org/sparql, with a simple SPARQL query like select distinct ?Concept where {[] a ?Concept} LIMIT 10 or similar. Use this plugin as a source dataset, and transform or transfer the SPARQL query results into a sink dataset such as a CSV file. A similar or related showcase example involves considering other output datasets such as an in-memory dataset or a Knowledge Graph such as the one handled by the eccencaDataPlatform plugin, which is the flagship RDF dataset of Corporate Memory.

Other types of RDF datasets are the in-memory dataset, the RDF dataset. These are worth considering if the information is short-lived or the dataset is small. A more durable and resilient solution is to use a proper Knowledge Graph.

The SPARQL dataset plugin can be used in conjunction with the task plugins for SPARQL SELECT, UPDATE and CONSTRUCT queries, i.e. the plugins sparqlSelectOperator, sparqlUpdateOperator and sparqlCopyOperator.

Parameter¤

Endpoint URI¤

The URI of the SPARQL endpoint, e.g. http://dbpedia.org/sparql

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

Login¤

Login required for authentication

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

Password¤

Password required for authentication

  • ID: password
  • Datatype: password
  • Default Value: None

Graph¤

The URI of a named graph. If set, the SPARQL endpoint will only retrieve entities from that specific graph.

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

Strategy¤

The strategy for retrieving entities. There are three options: simple retrieves all entities using a single query; subQuery also uses a single query, which is optimized for Virtuoso; parallel executes multiple queries in parallel, one for each entity property.

  • ID: strategy
  • Datatype: enumeration
  • Default Value: parallel

Use order by¤

Enforces the correct ordering of values, if set to true (default).

  • ID: useOrderBy
  • Datatype: boolean
  • Default Value: true

Clear graph before workflow execution¤

If set to true, this will clear the specified graph before executing a workflow that writes into it.

  • ID: clearGraphBeforeExecution
  • Datatype: boolean
  • Default Value: false

SPARQL query timeout (ms)¤

SPARQL query timeout in milliseconds. By default, a value of zero is used. This zero value has a symbolic character: it means that the timeout of SPARQL select and update queries is configured via the properties silk.remoteSparqlEndpoint.defaults.connection.timeout.ms andsilk.remoteSparqlEndpoint.defaults.read.timeout.ms` for the default connection and read timeouts. To overwrite these configured values, specify a (common) timeout greater than zero milliseconds.

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

Advanced Parameter¤

Page size¤

The number of entities to be retrieved per SPARQL query. This is the page size used when paging.

  • ID: pageSize
  • Datatype: int
  • Default Value: 1000

Entity list¤

An optional list of entities to be retrieved. If not specified, all entities will be retrieved. Multiple entities need to be separated by whitespace.

  • ID: entityList
  • Datatype: multiline string
  • Default Value: None

Pause time¤

The number of milliseconds to wait between subsequent queries

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

Retry count¤

The total number of retries to execute a (repeatedly) failing query

  • ID: retryCount
  • Datatype: int
  • Default Value: 3

Retry pause¤

The number of milliseconds to wait until a previously failed query is executed again

  • ID: retryPause
  • Datatype: int
  • Default Value: 1000

Query parameters¤

Additional parameters to be appended to every query, e.g. &soft-limit=1

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

Comments