diff --git a/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/oaf/DataInfo.java b/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/oaf/DataInfo.java
index 01a0396a8..1e3e451fc 100644
--- a/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/oaf/DataInfo.java
+++ b/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/oaf/DataInfo.java
@@ -10,54 +10,60 @@ public class DataInfo implements Serializable {
     private Boolean deletedbyinference;
     private String trust;
     private String inferenceprovenance;
-    private List<Qualifier> provenanceaction;
+    private Qualifier provenanceaction;
 
 
     public Boolean getInvisible() {
         return invisible;
     }
 
-    public void setInvisible(Boolean invisible) {
+    public DataInfo setInvisible(Boolean invisible) {
         this.invisible = invisible;
+        return this;
     }
 
     public Boolean getInferred() {
         return inferred;
     }
 
-    public void setInferred(Boolean inferred) {
+    public DataInfo setInferred(Boolean inferred) {
         this.inferred = inferred;
+        return this;
     }
 
     public Boolean getDeletedbyinference() {
         return deletedbyinference;
     }
 
-    public void setDeletedbyinference(Boolean deletedbyinference) {
+    public DataInfo setDeletedbyinference(Boolean deletedbyinference) {
         this.deletedbyinference = deletedbyinference;
+        return this;
     }
 
     public String getTrust() {
         return trust;
     }
 
-    public void setTrust(String trust) {
+    public DataInfo setTrust(String trust) {
         this.trust = trust;
+        return this;
     }
 
     public String getInferenceprovenance() {
         return inferenceprovenance;
     }
 
-    public void setInferenceprovenance(String inferenceprovenance) {
+    public DataInfo setInferenceprovenance(String inferenceprovenance) {
         this.inferenceprovenance = inferenceprovenance;
+        return this;
     }
 
-    public List<Qualifier> getProvenanceaction() {
+    public Qualifier getProvenanceaction() {
         return provenanceaction;
     }
 
-    public void setProvenanceaction(List<Qualifier> provenanceaction) {
+    public DataInfo setProvenanceaction(Qualifier provenanceaction) {
         this.provenanceaction = provenanceaction;
+        return this;
     }
 }
diff --git a/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/oaf/KeyValue.java b/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/oaf/KeyValue.java
index 1c4c7e6ef..efdeceef1 100644
--- a/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/oaf/KeyValue.java
+++ b/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/oaf/KeyValue.java
@@ -14,23 +14,26 @@ public class KeyValue implements Serializable {
         return key;
     }
 
-    public void setKey(String key) {
+    public KeyValue setKey(String key) {
         this.key = key;
+        return this;
     }
 
     public String getValue() {
         return value;
     }
 
-    public void setValue(String value) {
+    public KeyValue setValue(String value) {
         this.value = value;
+        return this;
     }
 
     public DataInfo getDataInfo() {
         return dataInfo;
     }
 
-    public void setDataInfo(DataInfo dataInfo) {
+    public KeyValue setDataInfo(DataInfo dataInfo) {
         this.dataInfo = dataInfo;
+        return this;
     }
 }
diff --git a/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/oaf/Qualifier.java b/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/oaf/Qualifier.java
index 0d917d50e..b586855a1 100644
--- a/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/oaf/Qualifier.java
+++ b/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/oaf/Qualifier.java
@@ -15,39 +15,44 @@ public class Qualifier implements Serializable {
         return classid;
     }
 
-    public void setClassid(String classid) {
+    public Qualifier setClassid(String classid) {
         this.classid = classid;
+        return this;
     }
 
     public String getClassname() {
         return classname;
     }
 
-    public void setClassname(String classname) {
+    public Qualifier setClassname(String classname) {
         this.classname = classname;
+        return this;
     }
 
     public String getSchemeid() {
         return schemeid;
     }
 
-    public void setSchemeid(String schemeid) {
+    public Qualifier setSchemeid(String schemeid) {
         this.schemeid = schemeid;
+        return this;
     }
 
     public String getSchemename() {
         return schemename;
     }
 
-    public void setSchemename(String schemename) {
+    public Qualifier setSchemename(String schemename) {
         this.schemename = schemename;
+        return this;
     }
 
     public DataInfo getDataInfo() {
         return dataInfo;
     }
 
-    public void setDataInfo(DataInfo dataInfo) {
+    public Qualifier setDataInfo(DataInfo dataInfo) {
         this.dataInfo = dataInfo;
+        return this;
     }
 }
diff --git a/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/oaf/Relation.java b/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/oaf/Relation.java
index 5cf0883be..db8807e21 100644
--- a/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/oaf/Relation.java
+++ b/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/oaf/Relation.java
@@ -20,47 +20,53 @@ public class Relation extends Oaf {
         return relType;
     }
 
-    public void setRelType(String relType) {
+    public Relation setRelType(String relType) {
         this.relType = relType;
+        return this;
     }
 
     public String getSubRelType() {
         return subRelType;
     }
 
-    public void setSubRelType(String subRelType) {
+    public Relation setSubRelType(String subRelType) {
         this.subRelType = subRelType;
+        return this;
     }
 
     public String getRelClass() {
         return relClass;
     }
 
-    public void setRelClass(String relClass) {
+    public Relation setRelClass(String relClass) {
         this.relClass = relClass;
+        return this;
     }
 
     public String getSource() {
         return source;
     }
 
-    public void setSource(String source) {
+    public Relation setSource(String source) {
         this.source = source;
+        return this;
     }
 
     public String getTarget() {
         return target;
     }
 
-    public void setTarget(String target) {
+    public Relation setTarget(String target) {
         this.target = target;
+        return this;
     }
 
     public List<KeyValue> getCollectedFrom() {
         return collectedFrom;
     }
 
-    public void setCollectedFrom(List<KeyValue> collectedFrom) {
+    public Relation setCollectedFrom(List<KeyValue> collectedFrom) {
         this.collectedFrom = collectedFrom;
+        return this;
     }
 }
diff --git a/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/oaf/StructuredProperty.java b/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/oaf/StructuredProperty.java
index 8a39d8d97..fc312e336 100644
--- a/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/oaf/StructuredProperty.java
+++ b/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/oaf/StructuredProperty.java
@@ -10,28 +10,30 @@ public class StructuredProperty implements Serializable {
 
     private DataInfo dataInfo;
 
-
     public String getValue() {
         return value;
     }
 
-    public void setValue(String value) {
+    public StructuredProperty setValue(String value) {
         this.value = value;
+        return this;
     }
 
     public Qualifier getQualifier() {
         return qualifier;
     }
 
-    public void setQualifier(Qualifier qualifier) {
+    public StructuredProperty setQualifier(Qualifier qualifier) {
         this.qualifier = qualifier;
+        return this;
     }
 
     public DataInfo getDataInfo() {
         return dataInfo;
     }
 
-    public void setDataInfo(DataInfo dataInfo) {
+    public StructuredProperty setDataInfo(DataInfo dataInfo) {
         this.dataInfo = dataInfo;
+        return this;
     }
 }
diff --git a/dhp-workflows/dhp-graph-mapper/src/main/java/eu/dnetlib/dhp/graph/ProtoUtils.java b/dhp-workflows/dhp-graph-mapper/src/main/java/eu/dnetlib/dhp/graph/ProtoUtils.java
new file mode 100644
index 000000000..b0f82ab00
--- /dev/null
+++ b/dhp-workflows/dhp-graph-mapper/src/main/java/eu/dnetlib/dhp/graph/ProtoUtils.java
@@ -0,0 +1,4 @@
+package eu.dnetlib.dhp.graph;
+
+public class ProtoUtils {
+}