diff --git a/src/main/java/envoy/server/data/Contact.java b/src/main/java/envoy/server/data/Contact.java
index 475b3ef..7ad1d6b 100644
--- a/src/main/java/envoy/server/data/Contact.java
+++ b/src/main/java/envoy/server/data/Contact.java
@@ -3,17 +3,7 @@ package envoy.server.data;
 import java.util.Date;
 import java.util.Set;
 
-import javax.persistence.CascadeType;
-import javax.persistence.Entity;
-import javax.persistence.FetchType;
-import javax.persistence.GeneratedValue;
-import javax.persistence.Id;
-import javax.persistence.Inheritance;
-import javax.persistence.InheritanceType;
-import javax.persistence.ManyToMany;
-import javax.persistence.Table;
-import javax.persistence.Temporal;
-import javax.persistence.TemporalType;
+import javax.persistence.*;
 
 /**
  * This class acts as a superclass for all contacts, being {@link User}s and
@@ -29,7 +19,7 @@ import javax.persistence.TemporalType;
 
 @Entity
 @Table(name = "contacts")
-@Inheritance(strategy = InheritanceType.JOINED)
+@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
 public abstract class Contact {
 
 	@Id
@@ -37,6 +27,7 @@ public abstract class Contact {
 	protected long		id;
 	protected String	name;
 
+	@Column(name = "creation_date")
 	@Temporal(TemporalType.TIMESTAMP)
 	private Date creationDate;
 
diff --git a/src/main/java/envoy/server/data/Group.java b/src/main/java/envoy/server/data/Group.java
index 5f3be22..bad4db9 100644
--- a/src/main/java/envoy/server/data/Group.java
+++ b/src/main/java/envoy/server/data/Group.java
@@ -5,7 +5,6 @@ import java.util.stream.Collectors;
 import javax.persistence.Entity;
 import javax.persistence.NamedQueries;
 import javax.persistence.NamedQuery;
-import javax.persistence.Table;
 
 /**
  * Represents a group inside the database. Referred to as "server group" as
@@ -19,7 +18,6 @@ import javax.persistence.Table;
  * @since Envoy Server Standalone v0.1-alpha
  */
 @Entity
-@Table(name = "groups")
 @NamedQueries({
 	@NamedQuery(
 		name = Group.findByName,
@@ -46,17 +44,11 @@ public class Group extends Contact {
 	 */
 	public static final String findPendingGroups = "Group.findPendingGroups";
 
-	/**
-	 * {@inheritDoc}
-	 */
 	@Override
 	public envoy.data.Group toCommon() {
 		return new envoy.data.Group(id, name, contacts.parallelStream().map(User.class::cast).map(User::toFlatCommon).collect(Collectors.toSet()));
 	}
 
-	/**
-	 * {@inheritDoc}
-	 */
 	@Override
 	protected envoy.data.Group toFlatCommon() { return toCommon(); }
 }
diff --git a/src/main/java/envoy/server/data/GroupMessage.java b/src/main/java/envoy/server/data/GroupMessage.java
index 4c64cf7..13dcc49 100644
--- a/src/main/java/envoy/server/data/GroupMessage.java
+++ b/src/main/java/envoy/server/data/GroupMessage.java
@@ -3,10 +3,7 @@ package envoy.server.data;
 import java.util.Date;
 import java.util.Map;
 
-import javax.persistence.ElementCollection;
-import javax.persistence.Entity;
-import javax.persistence.Temporal;
-import javax.persistence.TemporalType;
+import javax.persistence.*;
 
 import envoy.data.MessageBuilder;
 
@@ -24,6 +21,7 @@ public class GroupMessage extends Message {
 	@ElementCollection
 	private Map<Long, envoy.data.Message.MessageStatus> memberMessageStatus;
 
+	@Column(name = "last_status_change_date")
 	@Temporal(TemporalType.TIMESTAMP)
 	protected Date lastStatusChangeDate;
 
@@ -64,7 +62,6 @@ public class GroupMessage extends Message {
 			.setForwarded(forwarded)
 			.setStatus(status)
 			.setText(text)
-			// .setAttachment(attachment) TODO make this work
 			.buildGroupMessage((envoy.data.Group) recipient.toCommon(), memberMessageStatus);
 		groupMessage.setReceivedDate(receivedDate);
 		groupMessage.setReadDate(readDate);
diff --git a/src/main/java/envoy/server/data/Message.java b/src/main/java/envoy/server/data/Message.java
index 9203a4f..8a0a0ca 100755
--- a/src/main/java/envoy/server/data/Message.java
+++ b/src/main/java/envoy/server/data/Message.java
@@ -49,12 +49,15 @@ public class Message {
 	@JoinColumn
 	protected Contact recipient;
 
+	@Column(name = "creation_date")
 	@Temporal(TemporalType.TIMESTAMP)
 	protected Date creationDate;
 
+	@Column(name = "received_date")
 	@Temporal(TemporalType.TIMESTAMP)
 	protected Date receivedDate;
 
+	@Column(name = "read_date")
 	@Temporal(TemporalType.TIMESTAMP)
 	protected Date readDate;
 
@@ -88,7 +91,7 @@ public class Message {
 		sender			= persistenceManager.getUserByID(message.getSenderID());
 		recipient		= persistenceManager.getContactByID(message.getRecipientID());
 		forwarded		= message.isForwarded();
-		// TODO: attachment = message.getAttachment().toByteArray();DOES NOT WORK YET
+		// TODO: Attachment
 	}
 
 	/**
@@ -104,7 +107,6 @@ public class Message {
 			.setDate(creationDate)
 			.setStatus(status)
 			.setForwarded(forwarded)
-			// .setAttachment(attachment) TODO make this work
 			.build();
 		message.setReceivedDate(receivedDate);
 		message.setReadDate(readDate);
diff --git a/src/main/java/envoy/server/data/User.java b/src/main/java/envoy/server/data/User.java
index f1076c1..99941f4 100755
--- a/src/main/java/envoy/server/data/User.java
+++ b/src/main/java/envoy/server/data/User.java
@@ -22,7 +22,6 @@ import envoy.data.User.UserStatus;
  * @since Envoy Server Standalone v0.1-alpha
  */
 @Entity
-@Table(name = "users")
 @NamedQueries({
 	@NamedQuery(
 		name = User.findByName,
@@ -63,8 +62,10 @@ public class User extends Contact {
 	 */
 	public static final String searchByName = "User.searchByName";
 
+	@Column(name = "password_hash")
 	private byte[] passwordHash;
 
+	@Column(name = "last_seen")
 	@Temporal(TemporalType.TIMESTAMP)
 	private Date lastSeen;