Class: SPARQL::Client::Query

Inherits:
RDF::Query
  • Object
show all
Defined in:
lib/sparql/client/query.rb

Overview

A SPARQL query builder.

Examples:

Iterating over all found solutions

query.each_solution { |solution| puts solution.inspect }

Defined Under Namespace

Classes: Filter, WhereDecorator

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#self.construct(*variables, **options) ⇒ Query

Returns a new instance of Query.

Parameters:

Options Hash (**options):

  • :count (Hash{Symbol => Symbol}) —

    Contents are symbols relating a variable described within the query, to the projected variable.

Parameters:

  • form (Symbol, #to_s) (defaults to: :ask)

Yields:

Yield Parameters:



106
107
108
109
110
 
# File 'lib/sparql/client/query.rb', line 106

def initialize(form = :ask, **options, &block)
  @subqueries = []
  @form = form.respond_to?(:to_sym) ? form.to_sym : form.to_s.to_sym
  super([], **options, &block)
end

Instance Attribute Details

#form ⇒ :select, ... (readonly)

The form of the query.

Returns:

  • (:select, :ask, :construct, :describe)

See Also:



16
17
18
 
# File 'lib/sparql/client/query.rb', line 16

def form
  @form
end

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

Returns:

  • (Hash{Symbol => Object}) 


20
21
22
 
# File 'lib/sparql/client/query.rb', line 20

def options
  @options
end

Class Method Details

.ask(**options) ⇒ Query

Creates a boolean ‘ASK` query.

Examples:

ASK WHERE { ?s ?p ?o . }

Query.ask.where([:s, :p, :o])

Parameters:

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

    (see #initialize)

Returns:

See Also:



31
32
33
 
# File 'lib/sparql/client/query.rb', line 31

def self.ask(**options)
  self.new(:ask, **options)
end

.self.construct(*variables, **options) ⇒ Query

Creates a graph ‘CONSTRUCT` query.

Examples:

CONSTRUCT { ?s ?p ?o . } WHERE { ?s ?p ?o . }

Query.construct([:s, :p, :o]).where([:s, :p, :o])

Parameters:

  • patterns (Array<RDF::Query::Pattern, Array>)
  • options (Hash{Symbol => Object}) —

    (see #initialize)

Returns:

Parameters:

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

Returns:

See Also:



91
92
93
 
# File 'lib/sparql/client/query.rb', line 91

def self.construct(*patterns, **options)
  self.new(:construct, **options).construct(*patterns) # FIXME
end

.self.describe(*variables, **options) ⇒ Query

Creates a ‘DESCRIBE` query.

Examples:

DESCRIBE * WHERE { ?s ?p ?o . }

Query.describe.where([:s, :p, :o])

Parameters:

  • variables (Array<Symbol, RDF::URI>)
  • options (Hash{Symbol => Object}) —

    (see #initialize)

Returns:

Parameters:

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

Returns:

See Also:



73
74
75
 
# File 'lib/sparql/client/query.rb', line 73

def self.describe(*variables, **options)
  self.new(:describe, **options).describe(*variables)
end

.self.select(*variables, **options) ⇒ Query

Creates a tuple ‘SELECT` query.

Examples:

‘SELECT * WHERE { ?s ?p ?o . }`

Query.select.where([:s, :p, :o])

‘SELECT ?s WHERE ?p ?o .`

Query.select(:s).where([:s, :p, :o])

‘SELECT COUNT(?uri as ?c) WHERE a owl:Class`

Query.select(count: {uri: :c}).where([:uri, RDF.type, RDF::OWL.Class])

Parameters:

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

    (see #initialize)

Returns:

Parameters:

  • variables (Array<Symbol>)

Returns:

See Also:



55
56
57
 
# File 'lib/sparql/client/query.rb', line 55

def self.select(*variables, **options)
  self.new(:select, **options).select(*variables)
end

Instance Method Details

#asc(var) ⇒ Query

Examples:

SELECT * WHERE { ?s ?p ?o . } ORDER BY ASC(?o)

query.select.where([:s, :p, :o]).order.asc(:o)
query.select.where([:s, :p, :o]).asc(:o)

Parameters:

  • var (Array<Symbol, String>)

Returns:

See Also:



266
267
268
269
 
# File 'lib/sparql/client/query.rb', line 266

def asc(var)
  (options[:order_by] ||= []) << {var => :asc}
  self
end

#ask ⇒ Query

Examples:

ASK WHERE { ?s ?p ?o . }

query.ask.where([:s, :p, :o])

Returns:

See Also:



118
119
120
121
 
# File 'lib/sparql/client/query.rb', line 118

def ask
  @form = :ask
  self
end

#build_patterns(patterns) ⇒ Object 



623
624
625
 
# File 'lib/sparql/client/query.rb', line 623

def build_patterns(patterns)
  patterns.map {|pattern| RDF::Query::Pattern.from(pattern)}
end

#construct(*patterns) ⇒ Query

Examples:

CONSTRUCT { ?s ?p ?o . } WHERE { ?s ?p ?o . }

query.construct([:s, :p, :o]).where([:s, :p, :o])

Parameters:

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

Returns:

See Also:



166
167
168
169
 
# File 'lib/sparql/client/query.rb', line 166

def construct(*patterns)
  options[:template] = build_patterns(patterns)
  self
end

#desc(var) ⇒ Query

Examples:

SELECT * WHERE { ?s ?p ?o . } ORDER BY DESC(?o)

query.select.where([:s, :p, :o]).order.desc(:o)
query.select.where([:s, :p, :o]).desc(:o)

Parameters:

  • var (Array<Symbol, String>)

Returns:

See Also:



279
280
281
282
 
# File 'lib/sparql/client/query.rb', line 279

def desc(var)
  (options[:order_by] ||= []) << {var => :desc}
  self
end

#describe(*variables) ⇒ Query

Examples:

DESCRIBE * WHERE { ?s ?p ?o . }

query.describe.where([:s, :p, :o])

Parameters:

  • variables (Array<Symbol>)

Returns:

See Also:



152
153
154
155
156
157
 
# File 'lib/sparql/client/query.rb', line 152

def describe(*variables)
  @values = variables.map { |var|
    [var, var.is_a?(RDF::URI) ? var : RDF::Query::Variable.new(var)]
  }
  self
end

#distinct(state = true) ⇒ Query

Examples:

SELECT DISTINCT ?s WHERE { ?s ?p ?o . }

query.select(:s).distinct.where([:s, :p, :o])

Returns:

See Also:



304
305
306
307
 
# File 'lib/sparql/client/query.rb', line 304

def distinct(state = true)
  options[:distinct] = state
  self
end

#each_solution {|solution| ... } ⇒ Enumerator

Enumerates over each matching query solution.

Yields:

  • (solution)

Yield Parameters:

  • solution (RDF::Query::Solution)

Returns:

  • (Enumerator) 


672
673
674
675
 
# File 'lib/sparql/client/query.rb', line 672

def each_solution(&block)
  @solutions = result
  super
end

#each_statement {|statement| ... } ⇒ Enumerator

Yields:

  • (statement)

Yield Parameters:

  • (RDF::Statement)

Returns:

  • (Enumerator) 


663
664
665
 
# File 'lib/sparql/client/query.rb', line 663

def each_statement(&block)
  result.each_statement(&block)
end

#execute ⇒ Object

Returns:

  • (Object)

Raises:

  • (NotImplementedError) 


685
686
687
 
# File 'lib/sparql/client/query.rb', line 685

def execute
  raise NotImplementedError
end

#expects_statements? ⇒ Boolean

Returns expects_statements?.

Returns:

  • (Boolean) —

    expects_statements?



617
618
619
 
# File 'lib/sparql/client/query.rb', line 617

def expects_statements?
  [:construct, :describe].include?(form)
end

#false? ⇒ Boolean

Returns:

  • (Boolean) 


649
650
651
 
# File 'lib/sparql/client/query.rb', line 649

def false?
  !true?
end

#filter(string) ⇒ Query

Examples:

ASK WHERE { ?s ?p ?o . FILTER(regex(?s, ‘Abiline, Texas’)) }

query.ask.where([:s, :p, :o]).filter("regex(?s, 'Abiline, Texas')")

Returns:



631
632
633
634
 
# File 'lib/sparql/client/query.rb', line 631

def filter(string)
  ((options[:filters] ||= []) << Filter.new(string)) if string and not string.empty?
  self
end

#from(uri) ⇒ Query

Examples:

SELECT * FROM <a> WHERE { ?s ?p ?o . }

query.select.from(RDF::URI.new(a)).where([:s, :p, :o])

Parameters:

  • uri (RDF::URI)

Returns:

See Also:



178
179
180
181
 
# File 'lib/sparql/client/query.rb', line 178

def from(uri)
  options[:from] = uri
  self
end

#graph(graph_uri_or_var) ⇒ Query

Examples:

SELECT * WHERE { GRAPH ?g { ?s ?p ?o . } }

query.select.graph(:g).where([:s, :p, :o])

Parameters:

  • graph_uri_or_var (RDF::Value)

Returns:

See Also:



326
327
328
329
330
331
332
333
334
 
# File 'lib/sparql/client/query.rb', line 326

def graph(graph_uri_or_var)
  options[:graph] = case graph_uri_or_var
    when Symbol then RDF::Query::Variable.new(graph_uri_or_var)
    when String then RDF::URI(graph_uri_or_var)
    when RDF::Value then graph_uri_or_var
    else raise ArgumentError
  end
  self
end

#group(*variables) ⇒ Query Also known as: group_by

Examples:

SELECT ?s WHERE { ?s ?p ?o . } GROUP BY ?s

query.select(:s).where([:s, :p, :o]).group_by(:s)

Parameters:

  • variables (Array<Symbol, String>)

Returns:

See Also:



291
292
293
294
 
# File 'lib/sparql/client/query.rb', line 291

def group(*variables)
  options[:group_by] = variables
  self
end

#inspect ⇒ String

Returns a developer-friendly representation of this query.

Returns:

  • (String) 


836
837
838
 
# File 'lib/sparql/client/query.rb', line 836

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

#inspect! ⇒ void

This method returns an undefined value.

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



827
828
829
830
 
# File 'lib/sparql/client/query.rb', line 827

def inspect!
  warn(inspect)
  self
end

#limit(length) ⇒ Query

Examples:

SELECT * WHERE { ?s ?p ?o . } LIMIT 10

query.select.where([:s, :p, :o]).limit(10)

Parameters:

  • length (Integer, #to_i)

Returns:

See Also:



354
355
356
 
# File 'lib/sparql/client/query.rb', line 354

def limit(length)
  slice(nil, length)
end

#minus(*patterns) {|query| ... } ⇒ Query

The block form can be used for more complicated queries, using the ‘select` form (note, use either block or argument forms, not both):

Examples:

SELECT * WHERE { ?book dc:title ?title . MINUS { ?book dc11:title ?title } }

query.select.where([:book, RDF::Vocab::DC.title, :title]).
  minus([:book, RDF::Vocab::DC11.title, :title])

SELECT * WHERE { ?book dc:title ?title MINUS { ?book dc11:title ?title . FILTER(langmatches(lang(?title), ‘EN’)) } }

query1 = SPARQL::Client::Query.select.
  where([:book, RDF::Vocab::DC11.title, :title]).
  filter("langmatches(?title, 'en')")
query.select.where([:book, RDF::Vocab::DC.title, :title]).minus(query1)

SELECT * WHERE { ?book dc:title ?title MINUS { ?book dc11:title ?title . FILTER(langmatches(lang(?title), ‘EN’))} }

query1 = SPARQL::Client::Query.select.where([:book, RDF::Vocab::DC11.title, :title]).filter("langmatches(?title, 'en')")
query.select.where([:book, RDF::Vocab::DC.title, :title]).minus do |q|
  q.select.
    where([:book, RDF::Vocab::DC11.title, :title]).
    filter("langmatches(?title, 'en')")
end

Parameters:

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

    splat of zero or more patterns followed by zero or more queries.

Yields:

  • (query) —

    Yield form with or without argument; without an argument, evaluates within the query.

Yield Parameters:

Returns:

See Also:



525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
 
# File 'lib/sparql/client/query.rb', line 525

def minus(*patterns, &block)
  options[:minuses] ||= []

  if block_given?
    raise ArgumentError, "#minus requires either arguments or a block, not both." unless patterns.empty?
    # Evaluate calls in a new query instance
    query = self.class.select
    case block.arity
      when 1 then block.call(query)
      else query.instance_eval(&block)
    end
    options[:minuses] << query
  elsif patterns.all? {|p| p.is_a?(SPARQL::Client::Query)}
    # With argument form, all must be patterns or queries
    options[:minuses] += patterns
  elsif patterns.all? {|p| p.is_a?(Array)}
    # With argument form, all must be patterns, or queries
    options[:minuses] << self.class.select.where(*patterns)
  else
    raise ArgumentError, "#minus arguments are triple patters or queries, not both."
  end

  self
end

#offset(start) ⇒ Query

Examples:

SELECT * WHERE { ?s ?p ?o . } OFFSET 100

query.select.where([:s, :p, :o]).offset(100)

Parameters:

  • start (Integer, #to_i)

Returns:

See Also:



343
344
345
 
# File 'lib/sparql/client/query.rb', line 343

def offset(start)
  slice(start, nil)
end

#optional(*patterns) {|query| ... } ⇒ Query

The block form can be used for adding filters:

Examples:

SELECT * WHERE { ?s ?p ?o . OPTIONAL { ?s a ?o . ?s <purl.org/dc/terms/abstract> ?o . } }

query.select.where([:s, :p, :o]).
  optional([:s, RDF.type, :o], [:s, RDF::Vocab::DC.abstract, :o])

ASK WHERE { ?s ?p ?o . OPTIONAL { ?s ?p ?o . FILTER(regex(?s, ‘Abiline, Texas’))} }

query.ask.where([:s, :p, :o]).optional([:s, :p, :o]) do
  filter("regex(?s, 'Abiline, Texas')")
end

Parameters:

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

    splat of zero or more patterns followed by zero or more queries.

Yields:

  • (query) —

    Yield form with or without argument; without an argument, evaluates within the query.

Yield Parameters:

Returns:

See Also:



426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
 
# File 'lib/sparql/client/query.rb', line 426

def optional(*patterns, &block)
  (options[:optionals] ||= []) << build_patterns(patterns)

  if block_given?
    # Steal options[:filters]
    query_filters = options[:filters]
    options[:filters] = []
    case block.arity
      when 1 then block.call(self)
      else instance_eval(&block)
    end
    options[:optionals].last.concat(options[:filters])
    options[:filters] = query_filters
  end

  self
end

#order(*variables) ⇒ Query Also known as: order_by

Examples:

SELECT * WHERE { ?s ?p ?o . } ORDER BY ?o

query.select.where([:s, :p, :o]).order(:o)
query.select.where([:s, :p, :o]).order_by(:o)

SELECT * WHERE { ?s ?p ?o . } ORDER BY ?o ?p

query.select.where([:s, :p, :o]).order_by(:o, :p)

SELECT * WHERE { ?s ?p ?o . } ORDER BY ASC(?o) DESC(?p)

query.select.where([:s, :p, :o]).order_by(o: :asc, p: :desc)

Parameters:

  • variables (Array<Symbol, String>)

Returns:

See Also:



251
252
253
254
 
# File 'lib/sparql/client/query.rb', line 251

def order(*variables)
  options[:order_by] = variables
  self
end

#prefix(prefix: uri) ⇒ Query #prefix(string) ⇒ Query

Overloads:

  • #prefix(prefix: uri) ⇒ Query

    Examples:

    PREFIX dc: <purl.org/dc/elements/1.1/> PREFIX foaf: <xmlns.com/foaf/0.1/> SELECT * WHERE { ?s ?p ?o . }

    query.select.
  prefix(dc: RDF::URI("http://purl.org/dc/elements/1.1/")).
  prefix(foaf: RDF::URI("http://xmlns.com/foaf/0.1/")).
  where([:s, :p, :o])

    Parameters:

    • uri (RDF::URI)
    • prefix (Symbol, String) (defaults to: uri)

    Returns:

  • #prefix(string) ⇒ Query

    Examples:

    PREFIX dc: <purl.org/dc/elements/1.1/> PREFIX foaf: <xmlns.com/foaf/0.1/> SELECT * WHERE { ?s ?p ?o . }

    query.select.
  prefix("dc: <http://purl.org/dc/elements/1.1/>").
  prefix("foaf: <http://xmlns.com/foaf/0.1/>").
  where([:s, :p, :o])

    Parameters:

    • string (string)

    Returns:

See Also:



393
394
395
396
397
398
399
400
401
402
403
404
405
 
# File 'lib/sparql/client/query.rb', line 393

def prefix(val)
  options[:prefixes] ||= []
  if val.kind_of? String
    options[:prefixes] << val
  elsif val.kind_of? Hash
    val.each do |k, v|
      options[:prefixes] << "#{k}: <#{v}>"
    end
  else
    raise ArgumentError, "prefix must be a kind of String or a Hash"
  end
  self
end

#reduced(state = true) ⇒ Query

Examples:

SELECT REDUCED ?s WHERE { ?s ?p ?o . }

query.select(:s).reduced.where([:s, :p, :o])

Returns:

See Also:



315
316
317
318
 
# File 'lib/sparql/client/query.rb', line 315

def reduced(state = true)
  options[:reduced] = state
  self
end

#result ⇒ Object

Returns:

  • (Object) 


679
680
681
 
# File 'lib/sparql/client/query.rb', line 679

def result
  @result ||= execute
end

#select(*variables) ⇒ Query

Examples:

‘SELECT * WHERE { ?s ?p ?o . }`

query.select.where([:s, :p, :o])

‘SELECT ?s WHERE ?p ?o .`

query.select(:s).where([:s, :p, :o])

‘SELECT COUNT(?uri as ?c) WHERE a owl:Class`

query.select(count: {uri: :c}).where([:uri, RDF.type, RDF::OWL.Class])

Parameters:

  • variables (Array<Symbol>, Hash{Symbol => RDF::Query::Variable})

Returns:

See Also:



136
137
138
139
140
141
142
143
 
# File 'lib/sparql/client/query.rb', line 136

def select(*variables)
  @values = if variables.length == 1 && variables.first.is_a?(Hash)
    variables.to_a
  else
    variables.map { |var| [var, RDF::Query::Variable.new(var)] }
  end
  self
end

#slice(start, length) ⇒ Query

Examples:

SELECT * WHERE { ?s ?p ?o . } OFFSET 100 LIMIT 10

query.select.where([:s, :p, :o]).slice(100, 10)

Parameters:

  • start (Integer, #to_i)
  • length (Integer, #to_i)

Returns:



365
366
367
368
369
 
# File 'lib/sparql/client/query.rb', line 365

def slice(start, length)
  options[:offset] = start.to_i if start
  options[:limit] = length.to_i if length
  self
end

#solutions ⇒ Enumerable<RDF::Query::Solution>

Returns:

  • (Enumerable<RDF::Query::Solution>) 


655
656
657
 
# File 'lib/sparql/client/query.rb', line 655

def solutions
  result
end

#to_s ⇒ String

Returns the string representation of this query.

Returns:

  • (String) 


693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
 
# File 'lib/sparql/client/query.rb', line 693

def to_s
  buffer = [form.to_s.upcase]

  case form
    when :select, :describe
      only_count = values.empty? && options[:count]
      buffer << 'DISTINCT' if options[:distinct] and not only_count
      buffer << 'REDUCED'  if options[:reduced]
      buffer << ((values.empty? and not options[:count]) ? '*' : values.map { |v| SPARQL::Client.serialize_value(v[1]) }.join(' '))
      if options[:count]
        options[:count].each do |var, count|
          buffer << '( COUNT(' + (options[:distinct] ? 'DISTINCT ' : '') +
            (var.is_a?(String) ? var : "?#{var}") + ') AS ' + (count.is_a?(String) ? count : "?#{count}") + ' )'
        end
      end
    when :construct
      buffer << '{'
      buffer += SPARQL::Client.serialize_patterns(options[:template])
      buffer << '}'
  end

  buffer << "FROM #{SPARQL::Client.serialize_value(options[:from])}" if options[:from]

  unless patterns.empty? && form == :describe
    buffer += self.to_s_ggp.unshift('WHERE')
  end

  options.fetch(:unions, []).each do |query|
    buffer += query.to_s_ggp.unshift('UNION')
  end

  if options[:group_by]
    buffer << 'GROUP BY'
    buffer += options[:group_by].map { |var| var.is_a?(String) ? var : "?#{var}" }
  end

  if options[:order_by]
    buffer << 'ORDER BY'
    options[:order_by].map { |elem|
      case elem
        # .order_by({ var1: :asc, var2: :desc})
        when Hash
          elem.each { |key, val|
            # check provided values
            if !key.is_a?(Symbol)
              raise ArgumentError, 'keys of hash argument must be a Symbol'
            elsif !val.is_a?(Symbol) || (val != :asc && val != :desc)
              raise ArgumentError, 'values of hash argument must either be `:asc` or `:desc`'
            end
            buffer << "#{val == :asc ? 'ASC' : 'DESC'}(?#{key})"
          }
        # .order_by([:var1, :asc], [:var2, :desc])
        when Array
          # check provided values
          if elem.length != 2
            raise ArgumentError, 'array argument must specify two elements'
          elsif !elem[0].is_a?(Symbol)
            raise ArgumentError, '1st element of array argument must contain a Symbol'
          elsif !elem[1].is_a?(Symbol) || (elem[1] != :asc && elem[1] != :desc)
            raise ArgumentError, '2nd element of array argument must either be `:asc` or `:desc`'
          end
          buffer << "#{elem[1] == :asc ? 'ASC' : 'DESC'}(?#{elem[0]})"
        # .order_by(:var1, :var2)
        when Symbol
          buffer << "?#{elem}"
        # .order_by('ASC(?var1) DESC(?var2)')
        when String
          buffer << elem
        else
          raise ArgumentError, 'argument provided to `order()` must either be an Array, Symbol or String'
      end
    }
  end

  buffer << "OFFSET #{options[:offset]}" if options[:offset]
  buffer << "LIMIT #{options[:limit]}"   if options[:limit]
  options[:prefixes].reverse.each { |e| buffer.unshift("PREFIX #{e}") } if options[:prefixes]

  buffer.join(' ')
end

#to_s_ggp ⇒ Object

Serialize a Group Graph Pattern



776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
 
# File 'lib/sparql/client/query.rb', line 776

def to_s_ggp
  buffer = ["{"]

  if options[:graph]
    buffer << 'GRAPH ' + SPARQL::Client.serialize_value(options[:graph])
    buffer << '{'
  end

  @subqueries.each do |sq|
    buffer << "{ #{sq.to_s} } ."
  end

  buffer += SPARQL::Client.serialize_patterns(patterns)
  if options[:optionals]
    options[:optionals].each do |patterns|
      buffer << 'OPTIONAL {'
      buffer += SPARQL::Client.serialize_patterns(patterns)
      buffer << '}'
    end
  end
  if options[:filters]
    buffer += options[:filters].map(&:to_s)
  end
  if options[:values]
    vars = options[:values].first.map {|var| SPARQL::Client.serialize_value(var)}
    buffer << "VALUES (#{vars.join(' ')}) {"
    options[:values][1..-1].each do |data_block_value|
      buffer << '('
      buffer << data_block_value.map do |value|
        value.nil? ? 'UNDEF' : SPARQL::Client.serialize_value(value)
      end.join(' ')
      buffer << ')'
    end
    buffer << '}'
  end
  if options[:graph]
    buffer << '}' # GRAPH
  end

  options.fetch(:minuses, []).each do |query|
    buffer += query.to_s_ggp.unshift('MINUS')
  end

  buffer << '}'
  buffer
end

#true? ⇒ Boolean

Returns:

  • (Boolean) 


638
639
640
641
642
643
644
645
 
# File 'lib/sparql/client/query.rb', line 638

def true?
  case result
    when TrueClass, FalseClass then result
    when RDF::Literal::Boolean then result.true?
    when Enumerable then !result.empty?
    else false
  end
end

#union(*patterns) {|query| ... } ⇒ Query

The block form can be used for more complicated queries, using the ‘select` form (note, use either block or argument forms, not both):

Examples:

SELECT * WHERE { ?book dc:title ?title } UNION { ?book dc11:title ?title }

query.select.where([:book, RDF::Vocab::DC.title, :title]).
  union([:book, RDF::Vocab::DC11.title, :title])

SELECT * WHERE { ?book dc:title ?title } UNION { ?book dc11:title ?title . FILTER(langmatches(lang(?title), ‘EN’))}

query1 = SPARQL::Client::Query.select.
  where([:book, RDF::Vocab::DC11.title, :title]).
  filter("langmatches(?title, 'en')")
query.select.where([:book, RDF::Vocab::DC.title, :title]).union(query1)

SELECT * WHERE { ?book dc:title ?title } UNION { ?book dc11:title ?title . FILTER(langmatches(lang(?title), ‘EN’))}

query1 = SPARQL::Client::Query.select.where([:book, RDF::Vocab::DC11.title, :title]).filter("langmatches(?title, 'en')")
query.select.where([:book, RDF::Vocab::DC.title, :title]).union do |q|
  q.select.
    where([:book, RDF::Vocab::DC11.title, :title]).
    filter("langmatches(?title, 'en')")
end

Parameters:

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

    splat of zero or more patterns followed by zero or more queries.

Yields:

  • (query) —

    Yield form with or without argument; without an argument, evaluates within the query.

Yield Parameters:

Returns:

See Also:



472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
 
# File 'lib/sparql/client/query.rb', line 472

def union(*patterns, &block)
  options[:unions] ||= []

  if block_given?
    raise ArgumentError, "#union requires either arguments or a block, not both." unless patterns.empty?
    # Evaluate calls in a new query instance
    query = self.class.select
    case block.arity
      when 1 then block.call(query)
      else query.instance_eval(&block)
    end
    options[:unions] << query
  elsif patterns.all? {|p| p.is_a?(SPARQL::Client::Query)}
    # With argument form, all must be patterns or queries
    options[:unions] += patterns
  elsif patterns.all? {|p| p.is_a?(Array)}
    # With argument form, all must be patterns, or queries
    options[:unions] << self.class.select.where(*patterns)
  else
    raise ArgumentError, "#union arguments are triple patters or queries, not both."
  end

  self
end

#values ⇒ Array<Array(key, RDF::Value)> #values(vars, *data) ⇒ Query

Specify inline data for a query

Overloads:

  • #values ⇒ Array<Array(key, RDF::Value)>

    Values returned from previous query.

    Returns:

    • (Array<Array(key, RDF::Value)>)
  • #values(vars, *data) ⇒ Query

    Examples:

    single variable with multiple values

    query.select
 .where([:s, RDF::URI('http://purl.org/dc/terms/title'), :title])
 .values(:title, "This title", "Another title")

    multiple variables with multiple values

    query.select
 .where([:s, RDF::URI('http://purl.org/dc/terms/title'), :title],
        [:s, RDF.type, :type])
 .values([:type, :title],
         [RDF::URI('http://pcdm.org/models#Object'), "This title"],
         [RDF::URI('http://pcdm.org/models#Collection', 'Another title'])

    multiple variables with UNDEF

    query.select
 .where([:s, RDF::URI('http://purl.org/dc/terms/title'), :title],
        [:s, RDF.type, :type])
 .values([:type, :title],
         [nil "This title"],
         [RDF::URI('http://pcdm.org/models#Collection', nil])

    Parameters:

    • vars (Symbol, Array<Symbol>)
    • *data (Array<RDF::Term, String, nil>)

    Returns:



583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
 
# File 'lib/sparql/client/query.rb', line 583

def values(*args)
  return @values if args.empty?
  vars, *data = *args
  vars = Array(vars).map {|var| RDF::Query::Variable.new(var)}
  if vars.length == 1
    # data may be a in array form or simple form
    if data.any? {|d| d.is_a?(Array)} && !data.all? {|d| d.is_a?(Array)}
      raise ArgumentError, "values data must all be in array form or all simple"
    end
    data = data.map {|d| Array(d)}
  end

  # Each data value must be an array with the same number of entries as vars
  unless data.all? {|d| d.is_a?(Array) && d.all? {|dd| dd.is_a?(RDF::Value) || dd.is_a?(String) || dd.nil?}}
    raise ArgumentError, "values data must each be an array of terms, strings, or nil"
  end

  # Turn strings into Literals
  data = data.map do |d|
    d.map do |nil_literal_or_term|
      case nil_literal_or_term
      when nil then nil
      when String then RDF::Literal(nil_literal_or_term)
      when RDF::Value then nil_literal_or_term
      else raise ArgumentError
      end
    end
  end
  options[:values] = [vars, *data]
  self
end

#where(*patterns_queries) {|query| ... } ⇒ Query Also known as: whether

Block form can be used for chaining calls in addition to creating sub-select queries.

Examples:

SELECT * WHERE { ?s ?p ?o . }

query.select.where([:s, :p, :o])
query.select.whether([:s, :p, :o])

SELECT * WHERE { { SELECT * WHERE { ?s ?p ?o . } } . ?s ?p ?o . }

subquery = query.select.where([:s, :p, :o])
query.select.where([:s, :p, :o], subquery)

SELECT * WHERE { { SELECT * WHERE { ?s ?p ?o . } } . ?s ?p ?o . }

query.select.where([:s, :p, :o]) do |q|
  q.select.where([:s, :p, :o])
end

SELECT * WHERE { ?s ?p ?o . } ORDER BY ?o

query.select.where([:s, :p, :o]) do
  order(:o)
end

Parameters:

  • patterns_queries (Array<RDF::Query::Pattern, Array>) —

    splat of zero or more patterns followed by zero or more queries.

Yields:

  • (query) —

    Yield form with or without argument; without an argument, evaluates within the query.

Yield Parameters:

  • query (SPARQL::Client::Query) —

    Actually a delegator to query. Methods other than ‘#select` are evaluated against `self`. For `#select`, a new Query is created, and the result added as a subquery.

Returns:

See Also:



211
212
213
214
215
216
217
218
219
220
221
222
223
224
 
# File 'lib/sparql/client/query.rb', line 211

def where(*patterns_queries, &block)
  subqueries, patterns = patterns_queries.partition {|pq| pq.is_a? SPARQL::Client::Query}
  @patterns += build_patterns(patterns)
  @subqueries += subqueries

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