This is a sample script for doing linked data lookup starting with string input. The code pings the Library Of Congress /authorities/suggest OpenSearch service. If it finds an exact match, it will query the RDF graph looking for particular Predicates/Values. Further reasoning would be possible here as well. If it doesn't find a match, it will re…

authority_lookup_sample.rb

require 'net/http'
require 'json'
require 'linkeddata'

# API reference http://ruby-rdf.github.io/rdf/ 

#returned results from lookup
result = Hash.new

#define MADS vocabulary for RDF.ruby
MADS = RDF::Vocabulary.new("http://www.loc.gov/mads/rdf/v1#")

def get_loc_term(q)
  http = Net::HTTP.new("id.loc.gov")
  request = Net::HTTP::Get.new("/authorities/suggest/?q=#{q}") 
  response = http.request(request)
  if response.code != "200"
    puts "id.loc request error (status-code: #{response.code})\n#{response.body}"
  else
    data = JSON.parse(response.body)
    if q.eql? data[1][0] #if the search term matches the first hit exactly
      get_rdf(data[3][0]) #return the first result URI
    else
      data[1] #return search result set for user to choose
    end
  end
end

def get_rdf(uri)
  d = Hash.new
  d[:valueURI] = uri
  RDF::Reader.open(uri) do |reader|
    reader.each_statement do |statement|
      d[:scheme] =  statement.object if statement.predicate == MADS.isMemberOfMADSScheme && statement.subject == uri
      d[:madsCollection] =  statement.object if statement.predicate == MADS.isMemberOfMADSCollection && statement.subject == uri
      d[:authoritativeLabel] =  statement.object if statement.predicate == MADS.authoritativeLabel && statement.subject == uri
    end
  end
  d
end

#sample
a =  "Anti-fascist movements--Spain--Posters".split("--")
a.each { |term| 
  result[term] = get_loc_term(term)
}

#print results
puts result.inspect