Class: SPARQL::Client

Inherits:
Object
  • Object
show all
Defined in:
lib/sparql/client.rb,
lib/sparql/client/query.rb,
lib/sparql/client/update.rb,
lib/sparql/client/version.rb,
lib/sparql/client/repository.rb

Overview

A SPARQL 1.0/1.1 client for RDF.rb.

See Also:

Defined Under Namespace

Modules: Update, VERSION Classes: ClientError, MalformedQuery, Query, QueryElement, Repository, ServerError

Constant Summary collapse

RESULT_JSON = 
'application/sparql-results+json'.freeze
RESULT_XML = 
'application/sparql-results+xml'.freeze
RESULT_CSV = 
'text/csv'.freeze
RESULT_TSV = 
'text/tab-separated-values'.freeze
RESULT_BOOL =

Sesame-specific

'text/boolean'.freeze
RESULT_BRTR =

Sesame-specific

'application/x-binary-rdf-results-table'.freeze
RESULT_ALL = 
[
  RESULT_JSON,
  RESULT_XML,
  RESULT_BOOL,
  "#{RESULT_TSV};q=0.8",
  "#{RESULT_CSV};q=0.2",
  '*/*;q=0.1'
].join(', ').freeze
GRAPH_ALL = 
(
  RDF::Format.content_types.keys +
  ['*/*;q=0.1']
).join(', ').freeze
ACCEPT_JSON = 
{'Accept' => RESULT_JSON}.freeze
ACCEPT_XML = 
{'Accept' => RESULT_XML}.freeze
ACCEPT_CSV = 
{'Accept' => RESULT_CSV}.freeze
ACCEPT_TSV = 
{'Accept' => RESULT_TSV}.freeze
ACCEPT_BRTR = 
{'Accept' => RESULT_BRTR}.freeze
ACCEPT_RESULTS = 
{'Accept' => RESULT_ALL}.freeze
ACCEPT_GRAPH = 
{'Accept' => GRAPH_ALL}.freeze
DEFAULT_PROTOCOL = 
1.0
DEFAULT_METHOD = 
:post
XMLNS = 
{'sparql' => 'http://www.w3.org/2005/sparql-results#'}.freeze

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(url, options = {}, &block) ⇒ Client

Initialize a new sparql client, either using the URL of a SPARQL endpoint or an ‘RDF::Queryable` instance to use the native SPARQL gem.

Parameters:

  • url (String, RDF::Queryable, #to_s) —

    URL of endpoint, or queryable object.

  • options (Hash{Symbol => Object}) (defaults to: {})

Options Hash (options):

  • :method (Symbol) — default: DEFAULT_METHOD
  • :protocol (Number) — default: DEFAULT_PROTOCOL
  • :headers (Hash)
  • :read_timeout (Hash) 


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# File 'lib/sparql/client.rb', line 90

def initialize(url, options = {}, &block)
  case url
  when RDF::Queryable
    @url, @options = url, options.dup
  else
    @url, @options = RDF::URI.new(url.to_s), options.dup
    @headers = @options.delete(:headers) || {}
    @http = http_klass(@url.scheme)
  end

  if block_given?
    case block.arity
      when 1 then block.call(self)
      else instance_eval(&block)
    end
  end
end

Instance Attribute Details

#headers ⇒ Hash{String => String} (readonly)

The HTTP headers that will be sent in requests to the endpoint.

Returns:

  • (Hash{String => String}) 


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# File 'lib/sparql/client.rb', line 70

def headers
  @headers
end

#options ⇒ Hash{Symbol => Object} (readonly)

Any miscellaneous configuration.

Returns:

  • (Hash{Symbol => Object}) 


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# File 'lib/sparql/client.rb', line 76

def options
  @options
end

#url ⇒ RDF::URI, RDF::Queryable (readonly)

The SPARQL endpoint URL, or an RDF::Queryable instance, to use the native SPARQL engine.

Returns:

  • (RDF::URI, RDF::Queryable) 


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# File 'lib/sparql/client.rb', line 64

def url
  @url
end

Class Method Details

.parse_csv_bindings(csv, nodes = {}) ⇒ <RDF::Query::Solutions>

Parameters:

  • csv (String, Array<Array<String>>)

Returns:

  • (<RDF::Query::Solutions>)

See Also:



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# File 'lib/sparql/client.rb', line 425

def self.parse_csv_bindings(csv, nodes = {})
  require 'csv' unless defined?(::CSV)
  csv = CSV.parse(csv.to_s) unless csv.is_a?(Array)
  vars = csv.shift
  solutions = RDF::Query::Solutions.new
  csv.each do |row|
    solution = RDF::Query::Solution.new
    row.each_with_index do |v, i|
      term = case v
      when /^_:(.*)$/ then nodes[$1] ||= RDF::Node($1)
      when /^\w+:.*$/ then RDF::URI(v)
      else RDF::Literal(v)
      end
      solution[vars[i].to_sym] = term
    end
    solutions << solution
  end
  solutions
end

.parse_json_bindings(json, nodes = {}) ⇒ <RDF::Query::Solutions>

Parameters:

  • json (String, Hash)

Returns:

  • (<RDF::Query::Solutions>)

See Also:



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# File 'lib/sparql/client.rb', line 385

def self.parse_json_bindings(json, nodes = {})
  require 'json' unless defined?(::JSON)
  json = JSON.parse(json.to_s) unless json.is_a?(Hash)
  case
    when json.has_key?('boolean')
      json['boolean']
    when json.has_key?('results')
      solutions = json['results']['bindings'].map do |row|
        row = row.inject({}) do |cols, (name, value)|
          cols.merge(name.to_sym => parse_json_value(value, nodes))
        end
        RDF::Query::Solution.new(row)
      end
      RDF::Query::Solutions.new(solutions)
  end
end

.parse_json_value(value, nodes = {}) ⇒ RDF::Value

Parameters:

  • value (Hash{String => String})

Returns:

  • (RDF::Value)

See Also:



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# File 'lib/sparql/client.rb', line 407

def self.parse_json_value(value, nodes = {})
  case value['type'].to_sym
    when :bnode
      nodes[id = value['value']] ||= RDF::Node.new(id)
    when :uri
      RDF::URI.new(value['value'])
    when :literal
      RDF::Literal.new(value['value'], :datatype => value['datatype'], :language => value['xml:lang'])
    when :'typed-literal'
      RDF::Literal.new(value['value'], :datatype => value['datatype'])
    else nil
  end
end

.parse_tsv_bindings(tsv, nodes = {}) ⇒ <RDF::Query::Solutions>

Parameters:

  • tsv (String, Array<Array<String>>)

Returns:

  • (<RDF::Query::Solutions>)

See Also:



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# File 'lib/sparql/client.rb', line 449

def self.parse_tsv_bindings(tsv, nodes = {})
  tsv = tsv.lines.map {|l| l.chomp.split("\t")} unless tsv.is_a?(Array)
  vars = tsv.shift.map {|h| h.sub(/^\?/, '')}
  solutions = RDF::Query::Solutions.new
  tsv.each do |row|
    solution = RDF::Query::Solution.new
    row.each_with_index do |v, i|
      if !v.empty?
        term = RDF::NTriples.unserialize(v) || case v
        when /^\d+\.\d*[eE][+-]?[0-9]+$/  then RDF::Literal::Double.new(v)
        when /^\d*\.\d+[eE][+-]?[0-9]+$/  then RDF::Literal::Double.new(v)
        when /^\d*\.\d+$/                 then RDF::Literal::Decimal.new(v)
        when /^\d+$/                      then RDF::Literal::Integer.new(v)
        else
          RDF::Literal(v)
        end
        nodes[term.id] = term if term.is_a? RDF::Node
        solution[vars[i].to_sym] = term
      end
    end
    solutions << solution
  end
  solutions
end

.parse_xml_bindings(xml, nodes = {}) ⇒ <RDF::Query::Solutions>

Parameters:

  • xml (String, IO, Nokogiri::XML::Node, REXML::Element)

Returns:

  • (<RDF::Query::Solutions>)

See Also:



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# File 'lib/sparql/client.rb', line 478

def self.parse_xml_bindings(xml, nodes = {})
  xml.force_encoding(::Encoding::UTF_8) if xml.respond_to?(:force_encoding)

  if defined?(::Nokogiri)
    xml = Nokogiri::XML(xml).root unless xml.is_a?(Nokogiri::XML::Document)
    case
      when boolean = xml.xpath("//sparql:boolean", XMLNS)[0]
        boolean.text == 'true'
      when results = xml.xpath("//sparql:results", XMLNS)[0]
        solutions = results.elements.map do |result|
          row = {}
          result.elements.each do |binding|
            name  = binding.attr('name').to_sym
            value = binding.elements.first
            row[name] = parse_xml_value(value, nodes)
          end
          RDF::Query::Solution.new(row)
        end
        RDF::Query::Solutions.new(solutions)
    end
  else
    # REXML
    xml = REXML::Document.new(xml).root unless xml.is_a?(REXML::Element)
    case
      when boolean = xml.elements['boolean']
        boolean.text == 'true'
      when results = xml.elements['results']
        solutions = results.elements.map do |result|
          row = {}
          result.elements.each do |binding|
            name  = binding.attributes['name'].to_sym
            value = binding.select { |node| node.kind_of?(::REXML::Element) }.first
            row[name] = parse_xml_value(value, nodes)
          end
          RDF::Query::Solution.new(row)
        end
        RDF::Query::Solutions.new(solutions)
    end
  end
end

.parse_xml_value(value, nodes = {}) ⇒ RDF::Value

Parameters:

  • value (Nokogiri::XML::Element, REXML::Element)

Returns:

  • (RDF::Value)

See Also:



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# File 'lib/sparql/client.rb', line 523

def self.parse_xml_value(value, nodes = {})
  case value.name.to_sym
    when :bnode
      nodes[id = value.text] ||= RDF::Node.new(id)
    when :uri
      RDF::URI.new(value.text)
    when :literal
      lang     = value.respond_to?(:attr) ? value.attr('xml:lang') : value.attributes['xml:lang']
      datatype = value.respond_to?(:attr) ? value.attr('datatype') : value.attributes['datatype']
      RDF::Literal.new(value.text, :language => lang, :datatype => datatype)
    else nil
  end
end

.serialize_patterns(patterns, use_vars = false) ⇒ String

Serializes a SPARQL graph

Parameters:

  • patterns (RDF::Enumerable)
  • use_vars (Boolean) (defaults to: false) —

    (false) Use variables in place of BNodes

Returns:

  • (String) 


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# File 'lib/sparql/client.rb', line 610

def self.serialize_patterns(patterns, use_vars = false)
  patterns.map do |pattern|
    serialized_pattern = case pattern
    when SPARQL::Client::QueryElement then [pattern.to_s]
    else
      RDF::Statement.from(pattern).to_triple.each_with_index.map do |v, i|
        if i == 1
          SPARQL::Client.serialize_predicate(v)
       else
          SPARQL::Client.serialize_value(v, use_vars)
        end
      end
    end
    serialized_pattern.join(' ') + ' .'
  end
end

.serialize_predicate(value, rdepth = 0) ⇒ String

Serializes a SPARQL predicate

Parameters:

  • value (RDF::Value, Array, String)
  • rdepth (Fixnum) (defaults to: 0)

Returns:

  • (String) 


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# File 'lib/sparql/client.rb', line 589

def self.serialize_predicate(value,rdepth=0)
  case value
    when nil
      RDF::Query::Variable.new.to_s
    when String then value
    when Array
      s = value.map{|v|serialize_predicate(v,rdepth+1)}.join
      rdepth > 0 ? "(#{s})" : s
    when RDF::Value
      # abbreviate RDF.type in the predicate position per SPARQL grammar
      value.equal?(RDF.type) ? 'a' : serialize_value(value)
  end
end

.serialize_uri(uri) ⇒ String

Serializes a URI or URI string into SPARQL syntax.

Parameters:

  • uri (RDF::URI, String)

Returns:

  • (String) 


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# File 'lib/sparql/client.rb', line 556

def self.serialize_uri(uri)
  case uri
    when String then RDF::NTriples.serialize(RDF::URI(uri))
    when RDF::URI then RDF::NTriples.serialize(uri)
    else raise ArgumentError, "expected the graph URI to be a String or RDF::URI, but got #{uri.inspect}"
  end
end

.serialize_value(value, use_vars = false) ⇒ String

Serializes an ‘RDF::Value` into SPARQL syntax.

Parameters:

  • value (RDF::Value)
  • use_vars (Boolean) (defaults to: false) —

    (false) Use variables in place of BNodes

Returns:

  • (String) 


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# File 'lib/sparql/client.rb', line 571

def self.serialize_value(value, use_vars = false)
  # SPARQL queries are UTF-8, but support ASCII-style Unicode escapes, so
  # the N-Triples serializer is fine unless it's a variable:
  case
    when value.nil?      then RDF::Query::Variable.new.to_s
    when value.variable? then value.to_s
    when value.node?     then (use_vars ? RDF::Query::Variable.new(value.id) : value)
    else RDF::NTriples.serialize(value)
  end
end

Instance Method Details

#ask(*args) ⇒ Query

Executes a boolean ‘ASK` query.

Parameters:

  • options (Hash{Symbol => Object}) —

    (see #initialize)

Returns:



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# File 'lib/sparql/client.rb', line 113

def ask(*args)
  call_query_method(:ask, *args)
end

#call_query_method(meth, *args) ⇒ Object 



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# File 'lib/sparql/client.rb', line 266

def call_query_method(meth, *args)
  client = self
  result = Query.send(meth, *args)
  (class << result; self; end).send(:define_method, :execute) do
    client.query(self)
  end
  result
end

#clear(what, *arguments) ⇒ void #clear(what, *arguments, options = {}) ⇒ void

Executes a ‘CLEAR` operation.

This requires that the endpoint support SPARQL 1.1 Update.

Examples:

‘CLEAR GRAPH <example.org/>`

client.clear(:graph, RDF::URI("http://example.org/"))

‘CLEAR DEFAULT`

client.clear(:default)

‘CLEAR NAMED`

client.clear(:named)

‘CLEAR ALL`

client.clear(:all)

Overloads:

  • #clear(what, *arguments) ⇒ void

    This method returns an undefined value.

    Returns ‘self`.

    Parameters:

  • #clear(what, *arguments, options = {}) ⇒ void

    This method returns an undefined value.

    Returns ‘self`.

    Parameters:

    • what (Symbol, #to_sym)
    • arguments (Array) —

      splat of other arguments to SPARQL::Client::Update::Clear.

    • options (Hash{Symbol => Object}) (defaults to: {})

    Options Hash (options):

    • :silent (Boolean)

See Also:



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# File 'lib/sparql/client.rb', line 260

def clear(what, *arguments)
  self.update(Update::Clear.new(what, *arguments))
end

#clear_graph(graph_uri, options = {}) ⇒ void

This method returns an undefined value.

Executes a ‘CLEAR GRAPH` operation.

This is a convenience wrapper for the #clear method.

Examples:

‘CLEAR GRAPH <example.org/>`

client.clear_graph("http://example.org/")

Parameters:

  • graph_uri (RDF::URI, String)
  • options (Hash{Symbol => Object}) (defaults to: {})

Options Hash (options):

  • :silent (Boolean)

See Also:



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# File 'lib/sparql/client.rb', line 225

def clear_graph(graph_uri, options = {})
  self.clear(:graph, graph_uri, options)
end

#construct(*args) ⇒ Query

Executes a graph ‘CONSTRUCT` query.

Parameters:

  • patterns (Array<RDF::Query::Pattern, Array>)

Returns:



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# File 'lib/sparql/client.rb', line 140

def construct(*args)
  call_query_method(:construct, *args)
end

#delete_data(data, options = {}) ⇒ void

This method returns an undefined value.

Executes a ‘DELETE DATA` operation.

This requires that the endpoint support SPARQL 1.1 Update.

Examples:

Deleting data sourced from a file or URL

data = RDF::Graph.load("https://raw.githubusercontent.com/ruby-rdf/rdf/develop/etc/doap.nt")
client.delete_data(data)

Deleting data from a named graph

client.delete_data(data, :graph => "http://example.org/")

Parameters:

  • data (RDF::Enumerable)
  • options (Hash{Symbol => Object}) (defaults to: {})

Options Hash (options):

  • :graph (RDF::URI, String)

See Also:



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# File 'lib/sparql/client.rb', line 192

def delete_data(data, options = {})
  self.update(Update::DeleteData.new(data, options))
end

#delete_insert(delete_graph, insert_graph = nil, where_graph = nil, options = {}) ⇒ void

This method returns an undefined value.

Executes a ‘DELETE/INSERT` operation.

This requires that the endpoint support SPARQL 1.1 Update.

Parameters:

  • delete_graph (RDF::Enumerable)
  • insert_graph (RDF::Enumerable) (defaults to: nil)
  • where_graph (RDF::Enumerable) (defaults to: nil)
  • options (Hash{Symbol => Object}) (defaults to: {})

Options Hash (options):

  • :graph (RDF::URI, String)

See Also:



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# File 'lib/sparql/client.rb', line 208

def delete_insert(delete_graph, insert_graph = nil, where_graph = nil, options = {})
  self.update(Update::DeleteInsert.new(delete_graph, insert_graph, where_graph, options))
end

#describe(*args) ⇒ Query

Executes a ‘DESCRIBE` query.

Parameters:

  • variables (Array<Symbol, RDF::URI>)

Returns:



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# File 'lib/sparql/client.rb', line 131

def describe(*args)
  call_query_method(:describe, *args)
end

#insert_data(data, options = {}) ⇒ void

This method returns an undefined value.

Executes an ‘INSERT DATA` operation.

This requires that the endpoint support SPARQL 1.1 Update.

Note that for inserting non-trivial amounts of data, you probably ought to consider using the RDF store’s native bulk-loading facilities or APIs, as ‘INSERT DATA` operations entail comparably higher parsing overhead.

Examples:

Inserting data constructed ad-hoc

client.insert_data(RDF::Graph.new { |graph|
  graph << [:jhacker, RDF::Vocab::FOAF.name, "J. Random Hacker"]
})

Inserting data sourced from a file or URL

data = RDF::Graph.load("https://raw.githubusercontent.com/ruby-rdf/rdf/develop/etc/doap.nt")
client.insert_data(data)

Inserting data into a named graph

client.insert_data(data, :graph => "http://example.org/")

Parameters:

  • data (RDF::Enumerable)
  • options (Hash{Symbol => Object}) (defaults to: {})

Options Hash (options):

  • :graph (RDF::URI, String)

See Also:



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# File 'lib/sparql/client.rb', line 171

def insert_data(data, options = {})
  self.update(Update::InsertData.new(data, options))
end

#inspect ⇒ String

Returns a developer-friendly representation of this object.

Returns:

  • (String) 


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# File 'lib/sparql/client.rb', line 639

def inspect
  sprintf("#<%s:%#0x(%s)>", self.class.name, __id__, url.to_s)
end

#inspect! ⇒ void

This method returns an undefined value.

Outputs a developer-friendly representation of this object to ‘stderr`.



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# File 'lib/sparql/client.rb', line 631

def inspect!
  warn(inspect)
end

#nodes ⇒ Object

Returns a mapping of blank node results for this client.



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# File 'lib/sparql/client.rb', line 279

def nodes
  @nodes ||= {}
end

#parse_rdf_serialization(response, options = {}) ⇒ RDF::Enumerable

Parameters:

  • response (Net::HTTPSuccess)
  • options (Hash{Symbol => Object}) (defaults to: {})

Returns:

  • (RDF::Enumerable) 


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# File 'lib/sparql/client.rb', line 541

def parse_rdf_serialization(response, options = {})
  options = {:content_type => response.content_type} unless options[:content_type]
  if reader = RDF::Reader.for(options)
    reader.new(response.body)
  else
    raise RDF::ReaderError, "no RDF reader was found for #{options}."
  end
end

#parse_response(response, options = {}) ⇒ Object

Parameters:

  • response (Net::HTTPSuccess)
  • options (Hash{Symbol => Object}) (defaults to: {})

Returns:

  • (Object) 


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# File 'lib/sparql/client.rb', line 362

def parse_response(response, options = {})
  case options[:content_type] || response.content_type
    when NilClass
      response.body
    when RESULT_BOOL # Sesame-specific
      response.body == 'true'
    when RESULT_JSON
      self.class.parse_json_bindings(response.body, nodes)
    when RESULT_XML
      self.class.parse_xml_bindings(response.body, nodes)
    when RESULT_CSV
      self.class.parse_csv_bindings(response.body, nodes)
    when RESULT_TSV
      self.class.parse_tsv_bindings(response.body, nodes)
    else
      parse_rdf_serialization(response, options)
  end
end

#query(query, options = {}) ⇒ Array<RDF::Query::Solution>

Executes a SPARQL query and returns the parsed results.

Parameters:

  • query (String, #to_s)
  • options (Hash{Symbol => Object}) (defaults to: {})

Options Hash (options):

  • :content_type (String)
  • :headers (Hash)

Returns:

  • (Array<RDF::Query::Solution>)

See Also:



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# File 'lib/sparql/client.rb', line 292

def query(query, options = {})
  @op = :query
  @alt_endpoint = options[:endpoint]
  case @url
  when RDF::Queryable
    require 'sparql' unless defined?(::SPARQL::Grammar)
    begin
      SPARQL.execute(query, @url, options)
    rescue SPARQL::MalformedQuery
      $stderr.puts "error running #{query}: #{$!}"
      raise
    end
  else
    parse_response(response(query, options), options)
  end
end

#response(query, options = {}) ⇒ String

Executes a SPARQL query and returns the Net::HTTP::Response of the result.

Parameters:

  • query (String, #to_s)
  • options (Hash{Symbol => Object}) (defaults to: {})

Options Hash (options):

  • :content_type (String)
  • :headers (Hash)

Returns:

  • (String) 


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# File 'lib/sparql/client.rb', line 341

def response(query, options = {})
  headers = options[:headers] || {}
  headers['Accept'] = options[:content_type] if options[:content_type]
  request(query, headers) do |response|
    case response
      when Net::HTTPBadRequest  # 400 Bad Request
        raise MalformedQuery.new(response.body + " Processing query #{query}")
      when Net::HTTPClientError # 4xx
        raise ClientError.new(response.body + " Processing query #{query}")
      when Net::HTTPServerError # 5xx
        raise ServerError.new(response.body + " Processing query #{query}")
      when Net::HTTPSuccess     # 2xx
        response
    end
  end
end

#select(*args) ⇒ Query

Executes a tuple ‘SELECT` query.

Parameters:

  • variables (Array<Symbol>)

Returns:



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# File 'lib/sparql/client.rb', line 122

def select(*args)
  call_query_method(:select, *args)
end

#update(query, options = {}) ⇒ void

This method returns an undefined value.

Executes a SPARQL update operation.

Parameters:

  • query (String, #to_s)
  • options (Hash{Symbol => Object}) (defaults to: {})

Options Hash (options):

  • :endpoint (String)
  • :content_type (String)
  • :headers (Hash)

See Also:



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# File 'lib/sparql/client.rb', line 319

def update(query, options = {})
  @op = :update
  @alt_endpoint = options[:endpoint]
  case @url
  when RDF::Queryable
    require 'sparql' unless defined?(::SPARQL::Grammar)
    SPARQL.execute(query, @url, options.merge(update: true))
  else
    response(query, options)
  end
  self
end