lib/rdf/model/statement.rb in rdf-1.0.4 vs lib/rdf/model/statement.rb in rdf-1.0.5

@@ -104,9 +104,21 @@
     def statement?
       true
     end
 
     ##
+    # Returns `true` if any element of the statement is not a
+    # URI, Node or Literal.
+    #
+    # @return [Boolean]
+    def variable?
+      !(has_subject?    && subject.resource? && 
+        has_predicate?  && predicate.resource? &&
+        has_object?     && (object.resource? || object.literal?) &&
+        (has_context?    ? context.resource? : true ))
+    end
+
+    ##
     # @return [Boolean]
     def invalid?
       !valid?
     end