avoid blank nodes

Author: joergwa

patterns/TQC microstructure of ingot/shape-data.ttl

@@ -51,16 +51,16 @@ ex:segregation_factor_after_annealing a ex:cls_segregation_factor .
 ex:the_microstructure_before_annealing 
     is_state_of: ex:the_dual_ingot_and_microstructure ;
     has_quality: ex:segregation_factor_before_annealing ;
-    exists_at: [
-        a temporal_region:
-    ] .
+    exists_at: ex:region_1 .
+
+ex:region_1 a temporal_region: .
 
 ex:the_microstructure_after_annealing 
     is_state_of: ex:the_dual_ingot_and_microstructure ;
     has_quality: ex:segregation_factor_after_annealing ;
-    exists_at: [
-        a temporal_region:
-    ] .
+    exists_at: ex:region_2 .
+
+ex:region_2 a temporal_region: .
 
 # Link the states to their anchor and vice versa
 ex:the_dual_ingot_and_microstructure