diff --git a/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/dump/oaf/graph/Relation.java b/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/dump/oaf/graph/Relation.java
index 9fb5ea2df..664910f04 100644
--- a/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/dump/oaf/graph/Relation.java
+++ b/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/dump/oaf/graph/Relation.java
@@ -2,6 +2,7 @@
 package eu.dnetlib.dhp.schema.dump.oaf.graph;
 
 import java.io.Serializable;
+import java.util.Objects;
 
 import eu.dnetlib.dhp.schema.dump.oaf.Provenance;
 
@@ -42,4 +43,10 @@ public class Relation implements Serializable {
 	public void setProvenance(Provenance provenance) {
 		this.provenance = provenance;
 	}
+
+	@Override
+	public int hashCode() {
+
+		return Objects.hash(source.getId(), target.getId(), reltype.getType() + ":" + reltype.getName());
+	}
 }