diff --git a/src/main/java/eu/dnetlib/dhp/schema/dump/oaf/Author.java b/src/main/java/eu/dnetlib/dhp/schema/dump/oaf/Author.java
index c26bdd2..3c7710b 100644
--- a/src/main/java/eu/dnetlib/dhp/schema/dump/oaf/Author.java
+++ b/src/main/java/eu/dnetlib/dhp/schema/dump/oaf/Author.java
@@ -29,7 +29,8 @@ public class Author implements Serializable {
 
 	private Integer rank;
 
-	private Pid pid;
+	@JsonSchema(description="The author's persistent identifiers")
+	private AuthorPid pid;
 
 	public String getFullname() {
 		return fullname;
@@ -63,11 +64,11 @@ public class Author implements Serializable {
 		this.rank = rank;
 	}
 
-	public Pid getPid() {
+	public AuthorPid getPid() {
 		return pid;
 	}
 
-	public void setPid(Pid pid) {
+	public void setPid(AuthorPid pid) {
 		this.pid = pid;
 	}
 
diff --git a/src/main/java/eu/dnetlib/dhp/schema/dump/oaf/ControlledField.java b/src/main/java/eu/dnetlib/dhp/schema/dump/oaf/ControlledField.java
deleted file mode 100644
index cad7b8b..0000000
--- a/src/main/java/eu/dnetlib/dhp/schema/dump/oaf/ControlledField.java
+++ /dev/null
@@ -1,38 +0,0 @@
-
-package eu.dnetlib.dhp.schema.dump.oaf;
-
-import java.io.Serializable;
-
-/**
- * To represent the information described by a scheme and a value in that scheme (i.e. pid). It has two parameters: -
- * scheme of type String to store the scheme - value of type String to store the value in that scheme
- */
-public class ControlledField implements Serializable {
-	private String scheme;
-	private String value;
-
-	public String getScheme() {
-		return scheme;
-	}
-
-	public void setScheme(String scheme) {
-		this.scheme = scheme;
-	}
-
-	public String getValue() {
-		return value;
-	}
-
-	public void setValue(String value) {
-		this.value = value;
-	}
-
-	public static ControlledField newInstance(String scheme, String value) {
-		ControlledField cf = new ControlledField();
-
-		cf.setScheme(scheme);
-		cf.setValue(value);
-
-		return cf;
-	}
-}
diff --git a/src/main/java/eu/dnetlib/dhp/schema/dump/oaf/Pid.java b/src/main/java/eu/dnetlib/dhp/schema/dump/oaf/Pid.java
deleted file mode 100644
index 20848c6..0000000
--- a/src/main/java/eu/dnetlib/dhp/schema/dump/oaf/Pid.java
+++ /dev/null
@@ -1,44 +0,0 @@
-package eu.dnetlib.dhp.schema.dump.oaf;
-
-import java.io.Serializable;
-
-/**
- * To represent the generic persistent identifier. It has two parameters: - id of type
- * eu.dnetlib.dhp.schema.dump.oaf.ControlledField to store the scheme and value of the Persistent Identifier. -
- * provenance of type eu.dnetlib.dhp.schema.dump.oaf.Provenance to store the provenance and trust of the information
- */
-public class Pid implements Serializable {
-    private ControlledField id;
-    private Provenance provenance;
-
-    public ControlledField getId() {
-        return id;
-    }
-
-    public void setId(ControlledField pid) {
-        this.id = pid;
-    }
-
-    public Provenance getProvenance() {
-        return provenance;
-    }
-
-    public void setProvenance(Provenance provenance) {
-        this.provenance = provenance;
-    }
-
-    public static Pid newInstance(ControlledField pid, Provenance provenance) {
-        Pid p = new Pid();
-        p.id = pid;
-        p.provenance = provenance;
-
-        return p;
-    }
-
-    public static Pid newInstance(ControlledField pid) {
-        Pid p = new Pid();
-        p.id = pid;
-
-        return p;
-    }
-}
\ No newline at end of file
diff --git a/src/main/java/eu/dnetlib/dhp/schema/dump/oaf/Qualifier.java b/src/main/java/eu/dnetlib/dhp/schema/dump/oaf/Qualifier.java
deleted file mode 100644
index fd21424..0000000
--- a/src/main/java/eu/dnetlib/dhp/schema/dump/oaf/Qualifier.java
+++ /dev/null
@@ -1,38 +0,0 @@
-
-package eu.dnetlib.dhp.schema.dump.oaf;
-
-import java.io.Serializable;
-
-/**
- * To represent the information described by a code and a value It has two parameters: - code to store the code
- * (generally the classid of the eu.dnetlib.dhp.schema.oaf.Qualifier element) - label to store the label (generally the
- * classname of the eu.dnetlib.dhp.schema.oaf.Qualifier element
- */
-public class Qualifier implements Serializable {
-
-	private String code; // the classid in the Qualifier
-	private String label; // the classname in the Qualifier
-
-	public String getCode() {
-		return code;
-	}
-
-	public void setCode(String code) {
-		this.code = code;
-	}
-
-	public String getLabel() {
-		return label;
-	}
-
-	public void setLabel(String label) {
-		this.label = label;
-	}
-
-	public static Qualifier newInstance(String code, String value) {
-		Qualifier qualifier = new Qualifier();
-		qualifier.setCode(code);
-		qualifier.setLabel(value);
-		return qualifier;
-	}
-}
diff --git a/src/main/java/eu/dnetlib/dhp/schema/dump/oaf/Subject.java b/src/main/java/eu/dnetlib/dhp/schema/dump/oaf/Subject.java
index 204e37a..2edee2f 100644
--- a/src/main/java/eu/dnetlib/dhp/schema/dump/oaf/Subject.java
+++ b/src/main/java/eu/dnetlib/dhp/schema/dump/oaf/Subject.java
@@ -6,22 +6,26 @@ import java.io.Serializable;
 import com.github.imifou.jsonschema.module.addon.annotation.JsonSchema;
 
 /**
- * To represent keywords associated to the result. It has two parameters: - subject of type
- * eu.dnetlib.dhp.schema.dump.oaf.ControlledField to describe the subject. It mapped as: - schema it corresponds to
- * qualifier.classid of the dumped subject - value it corresponds to the subject value - provenance of type
- * eu.dnetlib.dhp.schema.dump.oaf.Provenance to represent the provenance of the subject. It is dumped only if dataInfo
- * is not null. In this case: - provenance corresponds to dataInfo.provenanceaction.classname - trust corresponds to
- * dataInfo.trust
+ * To represent keywords associated to the result. It has two parameters:
+ * - subject of type eu.dnetlib.dhp.schema.dump.oaf.SubjectSchemeValue to describe the subject. It mapped as:
+ * 		- schema it corresponds to qualifier.classid of the dumped subject
+ * 		- value it corresponds to the subject value
+ * - provenance of type eu.dnetlib.dhp.schema.dump.oaf.Provenance to represent the provenance of the subject. It is dumped only if dataInfo
+ * is not null. In this case:
+ * 		- provenance corresponds to dataInfo.provenanceaction.classname
+ * 		- trust corresponds to dataInfo.trust
  */
 public class Subject implements Serializable {
-	private ControlledField subject;
+	private SubjectSchemeValue subject;
+
+	@JsonSchema(description = "Why this subject is associated to the result")
 	private Provenance provenance;
 
-	public ControlledField getSubject() {
+	public SubjectSchemeValue getSubject() {
 		return subject;
 	}
 
-	public void setSubject(ControlledField subject) {
+	public void setSubject(SubjectSchemeValue subject) {
 		this.subject = subject;
 	}