diff --git a/YACOSCore/ejbModule/org/yacos/core/conferences/Conference.java b/YACOSCore/ejbModule/org/yacos/core/conferences/Conference.java
index d92f45c..9aa3402 100644
--- a/YACOSCore/ejbModule/org/yacos/core/conferences/Conference.java
+++ b/YACOSCore/ejbModule/org/yacos/core/conferences/Conference.java
@@ -1,7 +1,9 @@
 package org.yacos.core.conferences;
 
+import java.io.Serializable;
 import java.util.Collection;
 import java.util.Date;
+
 import javax.persistence.Entity;
 import javax.persistence.GeneratedValue;
 import javax.persistence.GenerationType;
@@ -16,7 +18,7 @@ import org.yacos.core.article.Article;
 import org.yacos.core.users.User;
 
 @Entity
-public class Conference {
+public class Conference implements Serializable{
 	@Id
 	@GeneratedValue(strategy=GenerationType.AUTO)
 	private Integer id;
@@ -34,31 +36,32 @@ public class Conference {
 	@Temporal(TemporalType.DATE)
 	private Date dateEnd;
 	
-	@OneToOne(targetEntity=User.class,optional=false)
-	@JoinColumn(name="chairman_id",nullable=false)
+	/*@OneToOne(targetEntity=User.class,optional=true)
+	@JoinColumn(name="chairman_id",nullable=true)
 	private User chairman;
-	
+	*/
 	@OneToMany(targetEntity=Article.class,mappedBy="conference")
 	private Collection<Article> articles;
 
 	/**
 	 * @return the chairman
 	 */
-	@OneToOne(targetEntity=User.class,optional=false)
-	@JoinColumn(name="chairman_id",nullable=false)
+	/*@OneToOne(targetEntity=User.class,optional=true)
+	@JoinColumn(name="chairman_id",nullable=true)
 	public User getChairman() {
 		return chairman;
 	}
-
+*/
 	/**
 	 * @param chairman the chairman to set
 	 */
-	@OneToOne(targetEntity=User.class,optional=false)
-	@JoinColumn(name="chairman_id",nullable=false)
+	/*
+	@OneToOne(targetEntity=User.class,optional=true)
+	@JoinColumn(name="chairman_id",nullable=true)
 	public void setChairman(User chairman) {
 		this.chairman = chairman;
 	}
-
+	*/
 	@Temporal(TemporalType.DATE)
     public Date getDataAbstract() {
 		return dateAbstract;
@@ -128,7 +131,7 @@ public class Conference {
 	public Conference() {
 	}
 	
-	public Conference(Integer id, String titre, String descirption, String infoComplementray, Date dataAbstract, Date dateArticle, Date dateEvaluation, Date dateStart, Date dateEnd) {
+	public Conference(String titre, String descirption, String infoComplementray, Date dataAbstract, Date dateArticle, Date dateEvaluation, Date dateStart, Date dateEnd) {
 		super();
 		this.id = id;
 		this.titre = titre;