Serialized asserted and embedded as subject triples using annotation syntax. {| ... |}.

Author: gkellogg

lib/rdf/turtle/writer.rb

@@ -380,10 +380,10 @@ def order_subjects
       # List elements which are bnodes should not be targets for top-level serialization
       list_elements = @lists.values.map(&:to_a).flatten.select(&:node?).compact
 
-      # Sort subjects by resources over bnodes, ref_counts and the subject URI itself
+      # Sort subjects by resources and statements over bnodes, ref_counts and the subject URI itself
       recursable = (@subjects.keys - list_elements).
         select {|s| !seen.include?(s)}.
-        map {|r| [r.node? ? 1 : 0, ref_count(r), r]}.
+        map {|r| [r.node? ? 2 : (r.statement? ? 1 : 0), ref_count(r), r]}.
         sort
 
       subjects + recursable.map{|r| r.last}
@@ -586,7 +586,7 @@ def predicate(resource)
     end
 
     # Render an objectList having a common subject and predicate
-    def objectList(objects)
+    def objectList(subject, predicate, objects)
       log_debug("objectList") {objects.inspect}
       return if objects.empty?
 
@@ -597,6 +597,15 @@ def objectList(objects)
           @output.write ",\n#{indent(4)}"
         end
         path(obj, :object)
+
+        # If subject, predicate, and object are embedded, write those bits out too.
+        emb = RDF::Statement(subject, predicate, obj)
+        if !@graph.query({subject: emb}).empty?
+          @output.write ' {| '
+          predicateObjectList(emb, true)
+          @output.write ' |}'
+          subject_done(emb)
+        end
       end
     end
 
@@ -616,10 +625,11 @@ def predicateObjectList(subject, from_bpl = false)
       @output.write("\n#{indent(2)}") if properties.keys.length > 1 && from_bpl
       prop_list.each_with_index do |prop, i|
         begin
+          pred = RDF::URI.intern(prop)
           @output.write(";\n#{indent(2)}") if i > 0
-          predicate(RDF::URI.intern(prop))
+          predicate(pred)
           @output.write(" ")
-          objectList(properties[prop])
+          objectList(subject, pred, properties[prop])
         end
       end
       properties.keys.length

spec/writer_spec.rb

@@ -707,6 +707,48 @@
         serialize(graph, params.fetch(:regexp, []), prefixes: {ex: 'http://example/'}, **params)
       end
     end
+
+    context "annotations" do
+      {
+        'turtle-star-annotation-1' => {
+          input: %(
+            PREFIX : <http://example/>
+            :s :p :o {| :r :z |} .
+          ),
+          regexp: [
+            %r(ex:s ex:p ex:o {\| ex:r ex:z \|} \.)
+          ]
+        },
+        'turtle-star-annotation-2' => {
+          input: %(
+            PREFIX :       <http://example/>
+            PREFIX xsd:     <http://www.w3.org/2001/XMLSchema#>
+
+            :s :p :o {| :source [ :graph <http://host1/> ;
+                                  :date "2020-01-20"^^xsd:date
+                                ] ;
+                        :source [ :graph <http://host2/> ;
+                                  :date "2020-12-31"^^xsd:date
+                                ]
+                      |} .
+          ),
+          regexp: [
+            %r(ex:s ex:p ex:o {\| ex:source \[),
+            %r(\s+ex:date "2020-01-20"\^\^<http://www.w3.org/2001/XMLSchema#date>;),
+            %r(\s+ex:graph <http://host1/>),
+            %r(\s+\], \[),
+            %r(\s+ex:date "2020-12-31"\^\^<http://www.w3.org/2001/XMLSchema#date>;),
+            %r(\s+ex:graph <http://host2/>),
+            %r(\s+\] \|} \.)
+          ]
+        }
+      }.each do |name, params|
+        it name do
+          graph = RDF::Graph.new {|g| g << parse(params[:input], rdfstar: true)}
+          serialize(graph, params.fetch(:regexp, []), prefixes: {ex: 'http://example/'}, **params)
+        end
+      end
+    end
   end
 
   # W3C Turtle Test suite from https://www.w3.org/TR/turtle/tests/