graph.rb in sparql-3.2.1

- old
+ new

@@ -5,31 +5,66 @@
     #
     # This is a wrapper to add a `graph_name` to the query, or an array of statements.
     #
     # [58]  GraphGraphPattern       ::= 'GRAPH' VarOrIri GroupGraphPattern
     #
-    # @example SPARQL Grammar
+    # @example SPARQL Grammar (query)
     #   PREFIX : <http://example/> 
     #   SELECT * { 
     #       GRAPH ?g { ?s ?p ?o }
     #   }
     #
     # @example SSE
     #   (prefix ((: <http://example/>))
     #    (graph ?g
     #     (bgp (triple ?s ?p ?o))))
     #
-    # @example of a query
+    # @example SPARQL Grammar (named set of statements)
+    #   PREFIX : <http://example/> 
+    #   SELECT * { 
+    #       GRAPH :g { :s :p :o }
+    #   }
+    #
+    # @example SSE (named set of statements)
     #   (prefix ((: <http://example/>))
+    #    (graph :g
+    #     (bgp (triple :s :p :o))))
+    #
+    # @example SPARQL Grammar (syntax-graph-05.rq)
+    #   PREFIX : <http://example.org/>
+    #   SELECT *
+    #   WHERE
+    #   {
+    #     :x :p :z
+    #     GRAPH ?g { :x :b ?a . GRAPH ?g2 { :x :p ?x } }
+    #   }
+    #
+    # @example SSE (syntax-graph-05.rq)
+    #   (prefix ((: <http://example.org/>))
+    #    (join
+    #     (bgp (triple :x :p :z))
     #     (graph ?g
-    #       (bgp (triple ?s ?p ?o))))
+    #      (join
+    #       (bgp (triple :x :b ?a))
+    #       (graph ?g2
+    #        (bgp (triple :x :p ?x)))))))
     #
-    # @example named set of statements
-    #   (prefix ((: <http://example/>))
-    #     (graph :g
-    #       ((triple :s :p :o))))
+    # @example SPARQL Grammar (pp06.rq)
+    #   prefix ex:	<http://www.example.org/schema#>
+    #   prefix in:	<http://www.example.org/instance#>
+    #   
+    #   select ?x where {
+    #     graph ?g {in:a ex:p1/ex:p2 ?x}
+    #   }
     #
+    # @example SSE (syntax-graph-05.rq)
+    #   (prefix ((ex: <http://www.example.org/schema#>)
+    #            (in: <http://www.example.org/instance#>))
+    #    (project (?x)
+    #     (graph ?g
+    #      (path in:a (seq ex:p1 ex:p2) ?x))))
+    #
     # @see https://www.w3.org/TR/sparql11-query/#sparqlAlgebra
     class Graph < Operator::Binary
       include Query
       
       NAME = [:graph]
@@ -86,9 +121,24 @@
       ##
       # Don't do any more rewriting
       # @return [SPARQL::Algebra::Expression] `self`
       def rewrite(&block)
         self
+      end
+
+      ##
+      #
+      # Returns a partial SPARQL grammar for this operator.
+      #
+      # @param [Boolean] top_level (true)
+      #   Treat this as a top-level, generating SELECT ... WHERE {}
+      # @return [String]
+      def to_sparql(top_level: true, **options)
+        query = operands.last.to_sparql(top_level: false, **options)
+        # Paths don't automatically get braces.
+        query = "{\n#{query}\n}" unless query.start_with?('{')
+        str = "GRAPH #{operands.first.to_sparql(**options)} " + query
+        top_level ? Operator.to_sparql(str, **options) : str
       end
     end # Graph
   end # Operator
 end; end # SPARQL::Algebra