diff --git a/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/oaf/Datasource.java b/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/oaf/Datasource.java
index f52a500fe6..032468de2f 100644
--- a/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/oaf/Datasource.java
+++ b/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/oaf/Datasource.java
@@ -40,9 +40,9 @@ public class Datasource extends OafEntity implements Serializable {
 
     private List<Field<String>> odlanguages;
 
-    private List< Field<String>> odcontenttypes;
+    private List<Field<String>> odcontenttypes;
 
-    private List< Field<String>> accessinfopackage;
+    private List<Field<String>> accessinfopackage;
 
     // re3data fields
     private Field<String> releasestartdate;
diff --git a/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/oaf/Field.java b/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/oaf/Field.java
index 2ab0b4d3c3..a75ed25c2b 100644
--- a/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/oaf/Field.java
+++ b/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/oaf/Field.java
@@ -12,16 +12,18 @@ public class Field<T> implements Serializable {
         return value;
     }
 
-    public void setValue(T value) {
+    public Field<T> setValue(T value) {
         this.value = value;
+        return this;
     }
 
     public DataInfo getDataInfo() {
         return dataInfo;
     }
 
-    public void setDataInfo(DataInfo dataInfo) {
+    public Field<T> setDataInfo(DataInfo dataInfo) {
         this.dataInfo = dataInfo;
+        return this;
     }
 
     @Override
diff --git a/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/oaf/Instance.java b/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/oaf/Instance.java
index 8f852af65d..06c907ee7c 100644
--- a/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/oaf/Instance.java
+++ b/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/oaf/Instance.java
@@ -26,68 +26,74 @@ public class Instance implements Serializable {
         return license;
     }
 
-    public void setLicense(Field<String> license) {
+    public Instance setLicense(Field<String> license) {
         this.license = license;
+        return this;
     }
 
     public Qualifier getAccessright() {
         return accessright;
     }
 
-    public void setAccessright(Qualifier accessright) {
+    public Instance setAccessright(Qualifier accessright) {
         this.accessright = accessright;
+        return this;
     }
 
     public Qualifier getInstancetype() {
         return instancetype;
     }
 
-    public void setInstancetype(Qualifier instancetype) {
+    public Instance setInstancetype(Qualifier instancetype) {
         this.instancetype = instancetype;
+        return this;
     }
 
     public KeyValue getHostedby() {
         return hostedby;
     }
 
-    public void setHostedby(KeyValue hostedby) {
+    public Instance setHostedby(KeyValue hostedby) {
         this.hostedby = hostedby;
+        return this;
     }
 
     public List<String> getUrl() {
         return url;
     }
 
-    public void setUrl(List<String> url) {
+    public Instance setUrl(List<String> url) {
         this.url = url;
+        return this;
     }
 
     public String getDistributionlocation() {
         return distributionlocation;
     }
 
-    public void setDistributionlocation(String distributionlocation) {
+    public Instance setDistributionlocation(String distributionlocation) {
         this.distributionlocation = distributionlocation;
+        return this;
     }
 
     public KeyValue getCollectedfrom() {
         return collectedfrom;
     }
 
-    public void setCollectedfrom(KeyValue collectedfrom) {
+    public Instance setCollectedfrom(KeyValue collectedfrom) {
         this.collectedfrom = collectedfrom;
+        return this;
     }
 
     public Field<String> getDateofacceptance() {
         return dateofacceptance;
     }
 
-    public void setDateofacceptance(Field<String> dateofacceptance) {
+    public Instance setDateofacceptance(Field<String> dateofacceptance) {
         this.dateofacceptance = dateofacceptance;
+        return this;
     }
 
-
-
     public String toComparableString(){
         return String.format("%s::%s::%s::%s",
                 hostedby != null && hostedby.getKey()!= null  ? hostedby.getKey().toLowerCase() : "",