Class: Qa::LinkedData::LdpathService

Inherits:

Object

• Object
• Qa::LinkedData::LdpathService

Defined in:

app/services/qa/linked_data/ldpath_service.rb

Constant Summary

VALUE_ON_ERROR =

[].freeze

Class Method Summary

• .ldpath_evaluate(program:, graph:, subject_uri:, limit_to_context: Qa.config.limit_ldpath_to_context?) ⇒ Array<String>

  Evaluate an ldpath for a specific subject uri in the context of a graph and return the extracted values.

• .ldpath_program(ldpath:, prefixes: {}) ⇒ Ldpath::Program

  Create the ldpath program for a given ldpath.

Class Method Details

.ldpath_evaluate(program:, graph:, subject_uri:, limit_to_context: Qa.config.limit_ldpath_to_context?) ⇒ Array<String>

Evaluate an ldpath for a specific subject uri in the context of a graph and return the extracted values.

Parameters:

• program (Ldpath::Program) —

  an executable program that will extract a value from a graph

• graph (RDF::Graph) —

  the graph from which the values will be extracted

• subject_uri (RDF::URI) —

  retrieved values will be limited to those with the subject uri

• limit_to_context (Boolean) (defaults to: Qa.config.limit_ldpath_to_context?) —

  if true, the evaluation process will not make any outside network calls. It will limit results to those found in the context graph.

Returns:

• (Array<String>) —

  the extracted values based on the ldpath

# File 'app/services/qa/linked_data/ldpath_service.rb', line 33

def self.ldpath_evaluate(program:, graph:, subject_uri:, limit_to_context: Qa.config.limit_ldpath_to_context?)
  return VALUE_ON_ERROR if program.blank?
  output = program.evaluate(subject_uri, context: graph, limit_to_context: limit_to_context)
  output.present? ? output['property'].uniq : nil
rescue => e
  Rails.logger.warn("WARNING: #{I18n.t('qa.linked_data.ldpath.evaluate_logger_error')} (cause: #{e.message}")
  raise StandardError, I18n.t("qa.linked_data.ldpath.evaluate_error") + "... cause: #{e.message}"
end

.ldpath_program(ldpath:, prefixes: {}) ⇒ Ldpath::Program

Create the ldpath program for a given ldpath.

Parameters:

• ldpath (String) —

  ldpath to follow to get a value from a graph (documation: marmotta.apache.org/ldpath/language.html)

• prefixes (Hash) (defaults to: {}) —

  shortcut names for URI prefixes with key = part of predicate that is the same for all terms (e.g. { “madsrdf”: “www.loc.gov/mads/rdf/v1#” })

Returns:

• (Ldpath::Program) —

  an executable program that will extract a value from a graph

# File 'app/services/qa/linked_data/ldpath_service.rb', line 16

def self.ldpath_program(ldpath:, prefixes: {})
  program_code = ""
  prefixes.each { |key, url| program_code << "@prefix #{key} : <#{url}> \;\n" }
  program_code << "property = #{ldpath} \;"
  Ldpath::Program.parse program_code
rescue => e
  Rails.logger.warn("WARNING: #{I18n.t('qa.linked_data.ldpath.parse_logger_error')}... cause: #{e.message}\n   ldpath_program=\n#{program_code}")
  raise StandardError, I18n.t("qa.linked_data.ldpath.parse_error") + "... cause: #{e.message}"
end