Update RDF* mode:

gkellogg · gkellogg · commit 819eb0516f47 · 2020-12-11T16:28:00.000-08:00
* Eliminate PG mode, `rdfstar` is not boolean valued.
* Change CLI from `--rdf-star` to `--rdfstar`.
* Update RDF* spec reference.

This follows the CG direction to not have modal operation, as annotations (in other serialization formats) more directly handle the PG use case.
diff --git a/README.md b/README.md
@@ -246,17 +246,10 @@ By default, the N-Triples reader will reject a document containing a subject res
     end
     # => RDF::ReaderError
 
-Readers support a `rdfstar` option with either `:PG` (Property Graph) or `:SA` (Separate Assertions) modes. In `:PG` mode, statements that are used in the subject or object positions are also implicitly added to the graph:
+Readers support a boolean valued `rdfstar` option.
 
     graph = RDF::Graph.new do |graph|
-      RDF::NTriples::Reader.new(nt, rdfstar: :PG) {|reader| graph << reader}
-    end
-    graph.count #=> 2
-
-When using the `:SA` mode, only one statement is asserted, although the reified statement is contained within the graph.
-
-    graph = RDF::Graph.new do |graph|
-      RDF::NTriples::Reader.new(nt, rdfstar: :SA) {|reader| graph << reader}
+      RDF::NTriples::Reader.new(nt, rdfstar: true) {|reader| graph << reader}
     end
     graph.count #=> 1
 
@@ -478,7 +471,7 @@ see <https://unlicense.org/> or the accompanying {file:UNLICENSE} file.
 [RDF::TriX]:        https://ruby-rdf.github.com/rdf-trix
 [RDF::Turtle]:      https://ruby-rdf.github.com/rdf-turtle
 [RDF::Raptor]:      https://ruby-rdf.github.com/rdf-raptor
-[RDF*]:             https://lists.w3.org/Archives/Public/public-rdf-star/
+[RDF*]:             https://w3c.github.io/rdf-star/rdf-star-cg-spec.html/
 [LinkedData]:       https://ruby-rdf.github.com/linkeddata
 [JSON::LD]:         https://ruby-rdf.github.com/json-ld
 [RestClient]:       https://rubygems.org/gems/rest-client
diff --git a/lib/rdf/nquads.rb b/lib/rdf/nquads.rb
@@ -69,9 +69,9 @@ def read_triple
 
           begin
             unless blank? || read_comment
-              subject   = read_uriref || read_node || read_rdfstar || fail_subject
+              subject   = read_uriref || read_node || read_embTriple || fail_subject
               predicate = read_uriref(intern: true) || fail_predicate
-              object    = read_uriref || read_node || read_literal || read_rdfstar || fail_object
+              object    = read_uriref || read_node || read_literal || read_embTriple || fail_object
               graph_name    = read_uriref || read_node
               if validate? && !read_eos
                 log_error("Expected end of statement (found: #{current_line.inspect})", lineno: lineno, exception: RDF::ReaderError)
diff --git a/lib/rdf/ntriples/reader.rb b/lib/rdf/ntriples/reader.rb
@@ -213,7 +213,7 @@ def read_value
       begin
         read_statement
       rescue RDF::ReaderError
-        value = read_uriref || read_node || read_literal || read_rdfstar
+        value = read_uriref || read_node || read_literal || read_embTriple
         log_recover
         value
       end
@@ -229,9 +229,9 @@ def read_triple
 
         begin
           unless blank? || read_comment
-            subject   = read_uriref || read_node || read_rdfstar || fail_subject
+            subject   = read_uriref || read_node || read_embTriple || fail_subject
             predicate = read_uriref(intern: true) || fail_predicate
-            object    = read_uriref || read_node || read_literal || read_rdfstar || fail_object
+            object    = read_uriref || read_node || read_literal || read_embTriple || fail_object
 
             if validate? && !read_eos
               log_error("Expected end of statement (found: #{current_line.inspect})", lineno: lineno, exception: RDF::ReaderError)
@@ -247,11 +247,11 @@ def read_triple
 
     ##
     # @return [RDF::Statement]
-    def read_rdfstar
+    def read_embTriple
       if @options[:rdfstar] && match(ST_START)
-        subject   = read_uriref || read_node || read_rdfstar || fail_subject
+        subject   = read_uriref || read_node || read_embTriple || fail_subject
         predicate = read_uriref(intern: true) || fail_predicate
-        object    = read_uriref || read_node || read_literal || read_rdfstar || fail_object
+        object    = read_uriref || read_node || read_literal || read_embTriple || fail_object
         if !match(ST_END)
           log_error("Expected end of statement (found: #{current_line.inspect})", lineno: lineno, exception: RDF::ReaderError)
         end
diff --git a/lib/rdf/ntriples/writer.rb b/lib/rdf/ntriples/writer.rb
@@ -227,7 +227,7 @@ def format_statement(statement, **options)
     # @param  [RDF::Statement] statement
     # @param  [Hash{Symbol => Object}] options ({})
     # @return [String]
-    def format_rdfstar(statement, **options)
+    def format_embTriple(statement, **options)
       "<<%s %s %s>>" % statement.to_a.map { |value| format_term(value, **options) }
     end
     ##
diff --git a/lib/rdf/query.rb b/lib/rdf/query.rb
@@ -255,7 +255,7 @@ def optimize(**options)
     # @see    RDF::Query::Pattern#cost
     # @since  0.3.0
     def optimize!(**options)
-      optional, required = @patterns.partition(&:optional?)
+      optional, required = @patterns.uniq.partition(&:optional?)
       required.sort! do |a, b|
         (a.cost || 0) <=> (b.cost || 0)
       end
diff --git a/lib/rdf/reader.rb b/lib/rdf/reader.rb
@@ -160,10 +160,9 @@ def self.options
         end,
         RDF::CLI::Option.new(
           symbol: :rdfstar,
-          control: :select,
-          datatype: [:PG, :SA],
-          on: ["--rdf-star MODE"],
-          description: "Parse RDF*, either in Property Graph mode (PG) or Separate Assertions mode (SA).") {|arg| arg.to_sym},
+          datatype: TrueClass,
+          on: ["--rdfstar"],
+          description: "Parse RDF*."),
         RDF::CLI::Option.new(
           symbol: :validate,
           datatype: TrueClass,
@@ -276,10 +275,8 @@ def to_sym
     #   the encoding of the input stream
     # @param [Boolean]  intern       (true)
     #   whether to intern all parsed URIs
-    # @param [:PG, :SA] rdfstar      (nil)
+    # @param [Boolean] rdfstar      (false)
     #   support parsing RDF* statement resources.
-    #   If `:PG`, referenced statements are also emitted.
-    #   If `:SA`, referenced statements are not emitted.
     # @param [Hash]     prefixes     (Hash.new)
     #   the prefix mappings to use (not supported by all readers)
     # @param  [Hash{Symbol => Object}] options
@@ -295,7 +292,7 @@ def initialize(input = $stdin,
                    encoding:      Encoding::UTF_8,
                    intern:        true,
                    prefixes:      Hash.new,
-                   rdfstar:       nil,
+                   rdfstar:       false,
                    validate:      false,
                    **options,
                    &block)
@@ -401,9 +398,6 @@ def prefix(name, uri = nil)
     # Statements are yielded in the order that they are read from the input
     # stream.
     #
-    # If the `rdfstar` option is `:PG` and triples include
-    # embedded statements, they are also enumerated.
-    #
     # @overload each_statement
     #   @yield  [statement]
     #     each statement
@@ -423,7 +417,6 @@ def each_statement(&block)
           loop do
             st = read_statement
             block.call(st)
-            each_pg_statement(st, &block) if options[:rdfstar] == :PG
           end
         rescue EOFError
           rewind rescue nil
@@ -441,9 +434,6 @@ def each_statement(&block)
     # Triples are yielded in the order that they are read from the input
     # stream.
     #
-    # If the `rdfstar` option is `:PG` and triples include
-    # embedded statements, they are also enumerated.
-    #
     # @overload each_triple
     #   @yield  [subject, predicate, object]
     #     each triple
@@ -464,10 +454,6 @@ def each_triple(&block)
           loop do
             triple = read_triple
             block.call(*triple)
-            if options[:rdfstar] == :PG
-              block.call(*triple[0].to_a) if triple[0].is_a?(Statement)
-              block.call(*triple[2].to_a) if triple[2].is_a?(Statement)
-            end
           end
         rescue EOFError
           rewind rescue nil
diff --git a/lib/rdf/writer.rb b/lib/rdf/writer.rb
@@ -516,7 +516,7 @@ def format_term(term, **options)
         when RDF::Literal   then format_literal(term, **options)
         when RDF::URI       then format_uri(term, **options)
         when RDF::Node      then format_node(term, **options)
-        when RDF::Statement then format_rdfstar(term, **options)
+        when RDF::Statement then format_embTriple(term, **options)
         else nil
       end
     end
@@ -574,7 +574,7 @@ def format_list(value, **options)
     # @return [String]
     # @raise  [NotImplementedError] unless implemented in subclass
     # @abstract
-    def format_rdfstar(value, **options)
+    def format_embTriple(value, **options)
       raise NotImplementedError.new("#{self.class}#format_statement") # override in subclasses
     end
 
diff --git a/spec/nquads_spec.rb b/spec/nquads_spec.rb
@@ -205,45 +205,21 @@
       end
     end
 
-    context "in property graph mode" do
-      statements.each do |name, st|
-        context name do
-          let(:graph) {RDF::Graph.new << RDF::NQuads::Reader.new(st, rdfstar: :PG)}
+    statements.each do |name, st|
+      context name do
+        let(:graph) {RDF::Graph.new << RDF::NQuads::Reader.new(st, rdfstar: true)}
 
-          it "creates two statements" do
-            expect(graph.count).to eql(2)
-          end
-
-          it "has a statement whose subject or object is a statement" do
-            referencing = graph.statements.detect {|s| s.predicate == RDF::URI("http://example/p")}
-            expect(referencing).to be_a_statement
-            if referencing.subject.statement?
-              expect(referencing.subject).to be_a_statement
-            else
-              expect(referencing.object).to be_a_statement
-            end
-          end
+        it "creates two statements" do
+          expect(graph.count).to eql(1)
         end
-      end
-    end
-
-    context "in separate assertions mode" do
-      statements.each do |name, st|
-        context name do
-          let(:graph) {RDF::Graph.new << RDF::NQuads::Reader.new(st, rdfstar: :SA)}
-
-          it "creates two statements" do
-            expect(graph.count).to eql(1)
-          end
 
-          it "has a statement whose subject or object is a statement" do
-            referencing = graph.statements.first
-            expect(referencing).to be_a_statement
-            if referencing.subject.statement?
-              expect(referencing.subject).to be_a_statement
-            else
-              expect(referencing.object).to be_a_statement
-            end
+        it "has a statement whose subject or object is a statement" do
+          referencing = graph.statements.first
+          expect(referencing).to be_a_statement
+          if referencing.subject.statement?
+            expect(referencing.subject).to be_a_statement
+          else
+            expect(referencing.object).to be_a_statement
           end
         end
       end
diff --git a/spec/ntriples_spec.rb b/spec/ntriples_spec.rb
@@ -428,49 +428,21 @@
       end
     end
 
-    context "in property graph mode" do
-      statements.each do |name, st|
-        context name do
-          let(:graph) {parse(st, rdfstar: :PG)}
-
-          it "creates two statements" do
-            expect(graph.count).to eql(2)
-          end unless name.to_s.include?('recursive')
-
-          it "creates multiple statements" do
-            expect(graph.count).to be > 2
-          end if name.to_s.include?('recursive')
-
-          it "has a statement whose subject or object is a statement" do
-            referencing = graph.statements.detect {|s| s.predicate == RDF::URI("http://example/p")}
-            expect(referencing).to be_a_statement
-            if referencing.subject.statement?
-              expect(referencing.subject).to be_a_statement
-            else
-              expect(referencing.object).to be_a_statement
-            end
-          end
-        end
-      end
-    end
+    statements.each do |name, st|
+      context name do
+        let(:graph) {parse(st, rdfstar: true)}
 
-    context "in separate assertions mode" do
-      statements.each do |name, st|
-        context name do
-          let(:graph) {parse(st, rdfstar: :SA)}
-
-          it "creates two statements" do
-            expect(graph.count).to eql(1)
-          end
+        it "creates two statements" do
+          expect(graph.count).to eql(1)
+        end
 
-          it "has a statement whose subject or object is a statement" do
-            referencing = graph.statements.first
-            expect(referencing).to be_a_statement
-            if referencing.subject.statement?
-              expect(referencing.subject).to be_a_statement
-            else
-              expect(referencing.object).to be_a_statement
-            end
+        it "has a statement whose subject or object is a statement" do
+          referencing = graph.statements.first
+          expect(referencing).to be_a_statement
+          if referencing.subject.statement?
+            expect(referencing.subject).to be_a_statement
+          else
+            expect(referencing.object).to be_a_statement
           end
         end
       end
