diff --git a/docs-core/src/main/java/com/sismics/docs/core/dao/jpa/GroupDao.java b/docs-core/src/main/java/com/sismics/docs/core/dao/jpa/GroupDao.java
new file mode 100644
index 00000000..955ac26c
--- /dev/null
+++ b/docs-core/src/main/java/com/sismics/docs/core/dao/jpa/GroupDao.java
@@ -0,0 +1,123 @@
+package com.sismics.docs.core.dao.jpa;
+
+import java.util.Date;
+import java.util.UUID;
+
+import javax.persistence.EntityManager;
+import javax.persistence.NoResultException;
+import javax.persistence.Query;
+
+import com.sismics.docs.core.constant.AuditLogType;
+import com.sismics.docs.core.model.jpa.Group;
+import com.sismics.docs.core.model.jpa.UserGroup;
+import com.sismics.docs.core.util.AuditLogUtil;
+import com.sismics.util.context.ThreadLocalContext;
+
+/**
+ * Group DAO.
+ * 
+ * @author bgamard
+ */
+public class GroupDao {
+    /**
+     * Gets a group by its ID.
+     * 
+     * @param id Group ID
+     * @return Group
+     */
+    public Group getById(String id) {
+        EntityManager em = ThreadLocalContext.get().getEntityManager();
+        try {
+            return em.find(Group.class, id);
+        } catch (NoResultException e) {
+            return null;
+        }
+    }
+    
+    /**
+     * Creates a new group.
+     * 
+     * @param group Group
+     * @param userId User ID
+     * @return New ID
+     * @throws Exception
+     */
+    public String create(Group group, String userId) {
+        // Create the UUID
+        group.setId(UUID.randomUUID().toString());
+        
+        // Create the group
+        EntityManager em = ThreadLocalContext.get().getEntityManager();
+        em.persist(group);
+        
+        // Create audit log
+        AuditLogUtil.create(group, AuditLogType.CREATE, userId);
+        
+        return group.getId();
+    }
+    
+    /**
+     * Deletes a group.
+     * 
+     * @param groupId Group ID
+     * @param userId User ID
+     */
+    public void delete(String groupId, String userId) {
+        EntityManager em = ThreadLocalContext.get().getEntityManager();
+            
+        // Get the group
+        Query q = em.createQuery("select g from Group g where g.id = :id and g.deleteDate is null");
+        q.setParameter("id", groupId);
+        Group groupDb = (Group) q.getSingleResult();
+        
+        // Delete the group
+        Date dateNow = new Date();
+        groupDb.setDeleteDate(dateNow);
+        
+        // Delete linked data
+        q = em.createQuery("update UserGroup ug set ug.deleteDate = :dateNow where ug.groupId = :groupId and ug.deleteDate is not null");
+        q.setParameter("dateNow", dateNow);
+        q.setParameter("groupId", groupId);
+        q.executeUpdate();
+
+        // Create audit log
+        AuditLogUtil.create(groupDb, AuditLogType.DELETE, userId);
+    }
+    
+    /**
+     * Add an user to a group.
+     * 
+     * @param group Group
+     * @return New ID
+     * @throws Exception
+     */
+    public String addMember(UserGroup userGroup) {
+        // Create the UUID
+        userGroup.setId(UUID.randomUUID().toString());
+        
+        // Create the user group
+        EntityManager em = ThreadLocalContext.get().getEntityManager();
+        em.persist(userGroup);
+        
+        return userGroup.getId();
+    }
+    
+    /**
+     * Remove an user from a group.
+     * 
+     * @param groupId Group ID
+     */
+    public void removeMember(String userGroupId) {
+        EntityManager em = ThreadLocalContext.get().getEntityManager();
+            
+        // Get the user group
+        Query q = em.createQuery("select ug from UserGroup ug where ug.id = :id and ug.deleteDate is null");
+        q.setParameter("id", userGroupId);
+        UserGroup userGroupDb = (UserGroup) q.getSingleResult();
+        
+        // Delete the user group
+        Date dateNow = new Date();
+        userGroupDb.setDeleteDate(dateNow);
+    }
+}
+
diff --git a/docs-core/src/main/java/com/sismics/docs/core/model/jpa/DocumentTag.java b/docs-core/src/main/java/com/sismics/docs/core/model/jpa/DocumentTag.java
index 51b0d51a..bacc47df 100644
--- a/docs-core/src/main/java/com/sismics/docs/core/model/jpa/DocumentTag.java
+++ b/docs-core/src/main/java/com/sismics/docs/core/model/jpa/DocumentTag.java
@@ -33,13 +33,13 @@ public class DocumentTag implements Serializable {
     /**
      * Document ID.
      */
-    @Column(name = "DOT_IDDOCUMENT_C", length = 36)
+    @Column(name = "DOT_IDDOCUMENT_C", nullable = false, length = 36)
     private String documentId;
     
     /**
      * Tag ID.
      */
-    @Column(name = "DOT_IDTAG_C", length = 36)
+    @Column(name = "DOT_IDTAG_C", nullable = false, length = 36)
     private String tagId;
 
     /**
@@ -83,6 +83,7 @@ public class DocumentTag implements Serializable {
     @Override
     public String toString() {
         return MoreObjects.toStringHelper(this)
+                .add("id", id)
                 .add("documentId", documentId)
                 .add("tagId", tagId)
                 .toString();
diff --git a/docs-core/src/main/java/com/sismics/docs/core/model/jpa/Group.java b/docs-core/src/main/java/com/sismics/docs/core/model/jpa/Group.java
new file mode 100644
index 00000000..b8981323
--- /dev/null
+++ b/docs-core/src/main/java/com/sismics/docs/core/model/jpa/Group.java
@@ -0,0 +1,91 @@
+package com.sismics.docs.core.model.jpa;
+
+import java.util.Date;
+
+import javax.persistence.Column;
+import javax.persistence.Entity;
+import javax.persistence.Id;
+import javax.persistence.Table;
+
+import com.google.common.base.MoreObjects;
+
+/**
+ * Group entity.
+ * 
+ * @author bgamard
+ */
+@Entity
+@Table(name = "T_GROUP")
+public class Group implements Loggable {
+    /**
+     * Group ID.
+     */
+    @Id
+    @Column(name = "GRP_ID_C", nullable = false, length = 36)
+    private String id;
+    
+    /**
+     * Vocabulary value.
+     */
+    @Column(name = "GRP_IDPARENT_C", length = 36)
+    private String parentId;
+    
+    /**
+     * Group name.
+     */
+    @Column(name = "GRP_NAME_C", nullable = false, length = 50)
+    private String name;
+
+    /**
+     * Deletion date.
+     */
+    @Column(name = "GRP_DELETEDATE_D")
+    private Date deleteDate;
+    
+    public String getId() {
+        return id;
+    }
+
+    public void setId(String id) {
+        this.id = id;
+    }
+
+    public String getParentId() {
+        return parentId;
+    }
+
+    public void setParentId(String parentId) {
+        this.parentId = parentId;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    @Override
+    public Date getDeleteDate() {
+        return deleteDate;
+    }
+    
+    public void setDeleteDate(Date deleteDate) {
+        this.deleteDate = deleteDate;
+    }
+    
+    @Override
+    public String toString() {
+        return MoreObjects.toStringHelper(this)
+                .add("id", id)
+                .add("parentId", parentId)
+                .add("name", name)
+                .toString();
+    }
+
+    @Override
+    public String toMessage() {
+        return name;
+    }
+}
diff --git a/docs-core/src/main/java/com/sismics/docs/core/model/jpa/UserGroup.java b/docs-core/src/main/java/com/sismics/docs/core/model/jpa/UserGroup.java
new file mode 100644
index 00000000..3ae2592a
--- /dev/null
+++ b/docs-core/src/main/java/com/sismics/docs/core/model/jpa/UserGroup.java
@@ -0,0 +1,91 @@
+package com.sismics.docs.core.model.jpa;
+
+import java.io.Serializable;
+import java.util.Date;
+
+import javax.persistence.Column;
+import javax.persistence.Entity;
+import javax.persistence.Id;
+import javax.persistence.Table;
+
+import com.google.common.base.MoreObjects;
+
+/**
+ * Link between an user and a group.
+ * 
+ * @author bgamard
+ */
+@Entity
+@Table(name = "T_USER_GROUP")
+public class UserGroup implements Serializable {
+    /**
+     * Serial version UID.
+     */
+    private static final long serialVersionUID = 1L;
+
+    /**
+     * User group ID.
+     */
+    @Id
+    @Column(name = "UGP_ID_C", length = 36)
+    private String id;
+    
+    /**
+     * User ID.
+     */
+    @Column(name = "UGP_IDUSER_C", nullable = false, length = 36)
+    private String userId;
+    
+    /**
+     * Group ID.
+     */
+    @Column(name = "UGP_IDGROUP_C", nullable = false, length = 36)
+    private String groupId;
+
+    /**
+     * Deletion date.
+     */
+    @Column(name = "UGP_DELETEDATE_D")
+    private Date deleteDate;
+    
+    public String getId() {
+        return id;
+    }
+
+    public void setId(String id) {
+        this.id = id;
+    }
+
+    public String getUserId() {
+        return userId;
+    }
+
+    public void setUserId(String userId) {
+        this.userId = userId;
+    }
+
+    public String getGroupId() {
+        return groupId;
+    }
+
+    public void setGroupId(String groupId) {
+        this.groupId = groupId;
+    }
+
+    public Date getDeleteDate() {
+        return deleteDate;
+    }
+
+    public void setDeleteDate(Date deleteDate) {
+        this.deleteDate = deleteDate;
+    }
+
+    @Override
+    public String toString() {
+        return MoreObjects.toStringHelper(this)
+                .add("id", id)
+                .add("userId", userId)
+                .add("groupId", groupId)
+                .toString();
+    }
+}
diff --git a/docs-core/src/main/resources/config.properties b/docs-core/src/main/resources/config.properties
index f4e9af41..fda5dfd0 100644
--- a/docs-core/src/main/resources/config.properties
+++ b/docs-core/src/main/resources/config.properties
@@ -1 +1 @@
-db.version=7
\ No newline at end of file
+db.version=8
\ No newline at end of file
diff --git a/docs-core/src/main/resources/db/update/dbupdate-008-0.sql b/docs-core/src/main/resources/db/update/dbupdate-008-0.sql
new file mode 100644
index 00000000..6f32919e
--- /dev/null
+++ b/docs-core/src/main/resources/db/update/dbupdate-008-0.sql
@@ -0,0 +1,4 @@
+create memory table T_GROUP ( GRP_ID_C varchar(36) not null, GRP_IDPARENT_C varchar(36), GRP_NAME_C varchar(50) not null, GRP_DELETEDATE_D datetime, primary key (GRP_ID_C) );
+create memory table T_USER_GROUP ( UGP_ID_C varchar(36) not null, UGP_IDUSER_C varchar(36) not null, UGP_IDGROUP_C varchar(36) not null, UGP_DELETEDATE_D datetime, primary key (UGP_ID_C) );
+
+update T_CONFIG set CFG_VALUE_C = '8' where CFG_ID_C = 'DB_VERSION';
diff --git a/docs-web/src/dev/resources/config.properties b/docs-web/src/dev/resources/config.properties
index 1bfb8fb0..44ddb414 100644
--- a/docs-web/src/dev/resources/config.properties
+++ b/docs-web/src/dev/resources/config.properties
@@ -1,3 +1,3 @@
 api.current_version=${project.version}
 api.min_version=1.0
-db.version=7
\ No newline at end of file
+db.version=8
\ No newline at end of file
diff --git a/docs-web/src/prod/resources/config.properties b/docs-web/src/prod/resources/config.properties
index 1bfb8fb0..44ddb414 100644
--- a/docs-web/src/prod/resources/config.properties
+++ b/docs-web/src/prod/resources/config.properties
@@ -1,3 +1,3 @@
 api.current_version=${project.version}
 api.min_version=1.0
-db.version=7
\ No newline at end of file
+db.version=8
\ No newline at end of file
diff --git a/docs-web/src/stress/resources/config.properties b/docs-web/src/stress/resources/config.properties
index 1bfb8fb0..44ddb414 100644
--- a/docs-web/src/stress/resources/config.properties
+++ b/docs-web/src/stress/resources/config.properties
@@ -1,3 +1,3 @@
 api.current_version=${project.version}
 api.min_version=1.0
-db.version=7
\ No newline at end of file
+db.version=8
\ No newline at end of file