Module: Krikri::ProvenanceQueryClient

Defined in:
lib/krikri/provenance_query_client.rb

Overview

Implements SPARQL queries for finding RDF Resources by their PROV-O history.

Constant Summary collapse

SPARQL_CLIENT = 
Repository.query_client

Class Method Summary collapse

Class Method Details

.find_by_activity(activity_uri, include_invalidated = false) ⇒ RDF::SPARQL::Query

Finds all entities generated or revised by the activity whose URI is given.

Parameters:

  • activity_uri (#to_uri) —

    the URI of the activity to search

  • include_invalidated (Boolean) (defaults to: false) —

    Whether to include entities that have been invalidated with <www.w3.org/ns/prov#invalidatedAtTime>

Returns:

  • (RDF::SPARQL::Query) —

    a query object that, when executed, will give solutions containing the URIs for the resources in ‘#record`.

Raises:

  • (ArgumentError)

See Also:



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# File 'lib/krikri/provenance_query_client.rb', line 23

def find_by_activity(activity_uri, include_invalidated = false)
  raise ArgumentError, 'activity_uri must be an RDF::URI' unless
    activity_uri.respond_to? :to_term
  query = SPARQL_CLIENT.select(:record)
    .where([:record,
            [RDF::PROV.wasGeneratedBy, '|', RDF::DPLA.wasRevisedBy],
            activity_uri.to_term])

  if include_invalidated
    query
  else
    # We need to say "and if RDF::PROV.invalidatedAtTime is not set."
    #
    # The SPARQL query should be:
    #
    # PREFIX prov: <http://www.w3.org/ns/prov#>
    # SELECT * WHERE {
    #   ?subject prov:wasGeneratedBy  <http://xampl.org/ldp/activity/n> .
    #   FILTER NOT EXISTS { ?subject prov:invalidatedAtTime ?x }
    # }
    #
    # ... However there doesn't appear to be a way of constructing
    # 'FILTER NOT EXISTS' with SPARQL::Client.  Instead, we've managed to
    # hack the following solution together.
    #
    # SPARQL::Client#filter is labeled @private in its YARD comment (and
    # has no other documentation) but it's not private, at least for
    # now.
    query.filter \
      'NOT EXISTS ' \
      '{ ?record <http://www.w3.org/ns/prov#invalidatedAtTime> ?x }'
  end
end