diff --git a/pom.xml b/pom.xml
index 172000b..eee9935 100644
--- a/pom.xml
+++ b/pom.xml
@@ -360,7 +360,12 @@
             <groupId>javax.persistence</groupId>
             <artifactId>javax.persistence-api</artifactId>
         </dependency>
-
+        <dependency>
+            <groupId>com.github.victools</groupId>
+            <artifactId>jsonschema-generator</artifactId>
+            <version>${jsonschemagenerator.version}</version>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
 
     <properties>
@@ -377,6 +382,7 @@
         <scala.version>2.11.12</scala.version>
         <junit-jupiter.version>5.6.1</junit-jupiter.version>
         <mockito-core.version>3.3.3</mockito-core.version>
+        <jsonschemagenerator.version>4.13.0</jsonschemagenerator.version>
     </properties>
 
 
diff --git a/src/main/java/eu/dnetlib/dhp/schema/dump/oaf/graph/Datasource.java b/src/main/java/eu/dnetlib/dhp/schema/dump/oaf/graph/Datasource.java
index 62a32a0..de845b3 100644
--- a/src/main/java/eu/dnetlib/dhp/schema/dump/oaf/graph/Datasource.java
+++ b/src/main/java/eu/dnetlib/dhp/schema/dump/oaf/graph/Datasource.java
@@ -93,7 +93,7 @@ public class Datasource implements Serializable {
 
 	private String certificates; // string
 
-	private List<Object> policies; //
+	private List<String> policies; //
 
 	private Container journal; // issn etc del Journal
 
@@ -297,11 +297,11 @@ public class Datasource implements Serializable {
 		this.certificates = certificates;
 	}
 
-	public List<Object> getPolicies() {
+	public List<String> getPolicies() {
 		return policies;
 	}
 
-	public void setPolicies(List<Object> policiesr3) {
+	public void setPolicies(List<String> policiesr3) {
 		this.policies = policiesr3;
 	}
 
diff --git a/src/test/java/eu/dnetlib/dhp/schema/oaf/dump/GenerateJsonSchema.java b/src/test/java/eu/dnetlib/dhp/schema/oaf/dump/GenerateJsonSchema.java
new file mode 100644
index 0000000..de1e77f
--- /dev/null
+++ b/src/test/java/eu/dnetlib/dhp/schema/oaf/dump/GenerateJsonSchema.java
@@ -0,0 +1,27 @@
+package eu.dnetlib.dhp.schema.oaf.dump;
+
+import org.junit.jupiter.api.Disabled;
+import org.junit.jupiter.api.Test;
+
+import com.fasterxml.jackson.databind.JsonNode;
+import com.github.victools.jsonschema.generator.*;
+
+import eu.dnetlib.dhp.schema.dump.oaf.graph.*;
+
+@Disabled
+class GenerateJsonSchema {
+
+    @Test
+    void generateSchema() {
+        SchemaGeneratorConfigBuilder configBuilder = new SchemaGeneratorConfigBuilder(SchemaVersion.DRAFT_7,
+                OptionPreset.PLAIN_JSON)
+                .with(Option.SCHEMA_VERSION_INDICATOR)
+                .without(Option.NONPUBLIC_NONSTATIC_FIELDS_WITHOUT_GETTERS);
+        configBuilder.forFields().withDescriptionResolver(field -> "Description of " + field.getDeclaredName());
+        SchemaGeneratorConfig config = configBuilder.build();
+        SchemaGenerator generator = new SchemaGenerator(config);
+        JsonNode jsonSchema = generator.generateSchema(GraphResult.class);
+
+        System.out.println(jsonSchema.toString());
+    }
+}