1. Certification
2. Group
3. Exam

1. One Certification can have multiple Groups (One-to-Many)
2. One Group can have multiple Exams and one Exam can belong to multiple Groups (Many-to-Many)
3. Exam data is created through a separate use case
4. While creating Certifications, the user can add new Groups and associate pre-exising Exams.

1. demo_cert
2. demo_grp (it has a FK to demo_cert's ID column)
3. demo_exam
4. demo_exam_grp(group_id, exam_id)

@Entity
@Table(name="demo_nn_cert")
@Access(AccessType.FIELD)
public class DemoCert
{
        @Id
   @Column(name="ID")
   @GeneratedValue(strategy=GenerationType.AUTO, generator="CERT_SEQ")
   @SequenceGenerator(name="CERT_SEQ", sequenceName="demo_cert_seq")
   private Long id;
   
   @OneToMany(fetch=FetchType.LAZY, cascade=CascadeType.ALL, orphanRemoval=true, mappedBy="demoCert", targetEntity=DemoGrp.class)
   private Set<DemoGrp> groups;
   
   @Version
   private long version;
   
   // -- Other properties and their getter/setters
}

@Entity
@Table(name="demo_nn_grp")
@Access(AccessType.FIELD)
public class DemoGrp implements Serializable
{
   /**
    *
    */
   private static final long serialVersionUID = 7438445502527409879L;

   @Id
   @Column(name="ID")
   @GeneratedValue(strategy=GenerationType.AUTO, generator="GROUP_SEQ")
   @SequenceGenerator(name="GROUP_SEQ", sequenceName="demo_group_seq")
   private Long id;
      
   @ManyToOne(cascade=CascadeType.ALL, fetch=FetchType.LAZY, targetEntity=DemoCert.class)
   @JoinColumn(name="CERT_ID")
   private DemoCert demoCert;
   
   @OneToMany(fetch=FetchType.LAZY, cascade=CascadeType.ALL, orphanRemoval=true, targetEntity=DemoExam.class)
   @JoinTable
   (
      name="DEMO_EXAM_GRP",
      joinColumns={@JoinColumn(name="GROUP_ID", referencedColumnName="ID")},
      inverseJoinColumns={@JoinColumn(name="EXAM_ID", referencedColumnName="ID")}
   )
   private Set<DemoExam> exams;
   
   // -- Other properties and getters/setters
}

@Entity
@Table(name="demo_nn_exam")
@Access(AccessType.FIELD)
public class DemoExam implements Serializable
{
   /**
    *
    */
   private static final long serialVersionUID = 375151244325884919L;

   @Id
   @Column(name="ID")
   private long id;
   
   @Version
   private long version;
   
   // -- Other properties and getters/setters
}

EntityManager.persist(demoCert)