diff --git a/obdalib/obdalib-core/src/main/java/inf/unibz/it/obda/rdbmsgav/domain/RDBMSOBDAMappingAxiom.java b/obdalib/obdalib-core/src/main/java/inf/unibz/it/obda/rdbmsgav/domain/RDBMSOBDAMappingAxiom.java
index <HASH>..<HASH> 100644
--- a/obdalib/obdalib-core/src/main/java/inf/unibz/it/obda/rdbmsgav/domain/RDBMSOBDAMappingAxiom.java
+++ b/obdalib/obdalib-core/src/main/java/inf/unibz/it/obda/rdbmsgav/domain/RDBMSOBDAMappingAxiom.java
@@ -87,4 +87,13 @@ public class RDBMSOBDAMappingAxiom extends AbstractOBDAMappingAxiom {
 
 		return clone;
 	}
+	
+	@Override
+	public String toString() {
+		StringBuffer bf = new StringBuffer();
+		bf.append(sourceQuery.toString());
+		bf.append(" ==> ");
+		bf.append(targetQuery.toString());
+		return bf.toString();
+	}
 }
Added comments, logging, documentation and TO-DOs to the classes involved in query answering.