diff --git a/src/main/kotlin/fr/postgresjson/entity/Entity.kt b/src/main/kotlin/fr/postgresjson/entity/Entity.kt
index 446b98a..0ca917a 100644
--- a/src/main/kotlin/fr/postgresjson/entity/Entity.kt
+++ b/src/main/kotlin/fr/postgresjson/entity/Entity.kt
@@ -1,126 +1,5 @@
 package fr.postgresjson.entity
 
-import org.joda.time.DateTime
-import java.util.*
-
 interface Serializable
 interface EntityI : Serializable
 interface Parameter : Serializable
-
-abstract class Entity<T>(open var id: T? = null) : EntityI
-open class UuidEntity(override var id: UUID? = UUID.randomUUID()) : Entity<UUID>(id)
-open class IdEntity(override var id: Int? = null) : Entity<Int>(id)
-
-/* Version */
-interface EntityVersioning<ID, NUMBER> {
-    var versionId: ID
-    var versionNumber: NUMBER?
-}
-
-class UuidEntityVersioning : EntityVersioning<UUID, Int> {
-    override var versionId: UUID = UUID.randomUUID()
-    override var versionNumber: Int? = null
-}
-
-/* Dates */
-interface EntityCreatedAt {
-    var createdAt: DateTime?
-}
-
-interface EntityUpdatedAt {
-    var updatedAt: DateTime?
-}
-
-interface EntityDeletedAt {
-    var deletedAt: DateTime?
-    fun isDeleted(): Boolean {
-        val deletedAt = deletedAt
-        return deletedAt != null && deletedAt < DateTime.now()
-    }
-}
-
-class EntityCreatedAtImp : EntityCreatedAt {
-    override var createdAt: DateTime? = null
-}
-
-class EntityUpdatedAtImp : EntityUpdatedAt {
-    override var updatedAt: DateTime? = null
-}
-
-class EntityDeletedAtImp : EntityDeletedAt {
-    override var deletedAt: DateTime? = null
-}
-
-/* Author */
-interface EntityCreatedBy<T : EntityI> {
-    var createdBy: T?
-}
-
-interface EntityUpdatedBy<T : EntityI> {
-    var updatedBy: T?
-}
-
-interface EntityDeletedBy<T : EntityI> {
-    var deletedBy: T?
-}
-
-class EntityCreatedByImp<UserT : EntityI>(
-    override var createdBy: UserT?
-) : EntityCreatedBy<UserT>
-
-class EntityUpdatedByImp<UserT : EntityI>(
-    override var updatedBy: UserT?
-) : EntityUpdatedBy<UserT>
-
-class EntityDeletedByImp<UserT : EntityI>(
-    override var deletedBy: UserT?
-) : EntityDeletedBy<UserT>
-
-/* Mixed */
-class EntityDeletedImp<UserT : EntityI>(
-    override var deletedBy: UserT? = null
-) : EntityDeletedBy<UserT>,
-    EntityDeletedAt by EntityDeletedAtImp()
-
-class EntityUpdatedImp<UserT : EntityI>(
-    override var updatedAt: DateTime? = null,
-    override var updatedBy: UserT? = null
-) : EntityUpdatedBy<UserT>,
-    EntityUpdatedAt by EntityUpdatedAtImp()
-
-class EntityCreatedImp<UserT : EntityI>(
-    override var createdAt: DateTime? = null,
-    override var createdBy: UserT? = null
-) : EntityCreatedBy<UserT>,
-    EntityCreatedAt by EntityCreatedAtImp()
-
-/* Published */
-interface Published<UserT : EntityI> {
-    var publishedAt: DateTime?
-    var publishedBy: UserT?
-}
-
-class EntityPublishedImp<UserT : EntityI>(
-    override var publishedBy: UserT?
-) : Published<UserT> {
-    override var publishedAt: DateTime? = null
-}
-
-/* Implementation */
-abstract class EntityImp<T, UserT : EntityI>(
-    updatedBy: UserT?
-) : Entity<T>(),
-    EntityCreatedAt by EntityCreatedAtImp(),
-    EntityUpdatedAt by EntityUpdatedAtImp(),
-    EntityDeletedAt by EntityDeletedAtImp(),
-    EntityCreatedBy<UserT> by EntityCreatedByImp(updatedBy),
-    EntityUpdatedBy<UserT> by EntityUpdatedByImp(updatedBy),
-    EntityDeletedBy<UserT> by EntityDeletedByImp(updatedBy)
-
-abstract class UuidEntityExtended<T, UserT : EntityI>(
-    updatedBy: UserT?,
-    publishedBy: UserT?
-) :
-    EntityImp<T, UserT>(updatedBy),
-    EntityVersioning<UUID, Int> by UuidEntityVersioning(),
-    Published<UserT> by EntityPublishedImp(publishedBy)
diff --git a/src/main/kotlin/fr/postgresjson/entity/immutable/ImmutableEntity.kt b/src/main/kotlin/fr/postgresjson/entity/immutable/ImmutableEntity.kt
new file mode 100644
index 0000000..6ed1324
--- /dev/null
+++ b/src/main/kotlin/fr/postgresjson/entity/immutable/ImmutableEntity.kt
@@ -0,0 +1,88 @@
+package fr.postgresjson.entity.immutable
+
+import fr.postgresjson.entity.EntityI
+import fr.postgresjson.entity.mutable.EntityDeletedAt
+import fr.postgresjson.entity.mutable.EntityDeletedAtImp
+import fr.postgresjson.entity.mutable.EntityDeletedBy
+import fr.postgresjson.entity.mutable.EntityDeletedByImp
+import org.joda.time.DateTime
+import java.util.*
+
+interface EntityRefI<T> : EntityI {
+    val id: T
+}
+
+interface UuidEntityI : EntityRefI<UUID> {
+    override val id: UUID
+}
+
+abstract class Entity<T>(override val id: T) : EntityRefI<T>
+open class UuidEntity(override val id: UUID = UUID.randomUUID()) : UuidEntityI, Entity<UUID>(id)
+
+/* Version */
+interface EntityVersioning<ID, NUMBER> {
+    val versionId: ID
+    val versionNumber: NUMBER
+}
+
+class UuidEntityVersioning(
+    override val versionNumber: Int,
+    override val versionId: UUID = UUID.randomUUID()
+) : EntityVersioning<UUID, Int>
+
+/* Dates */
+interface EntityCreatedAt {
+    val createdAt: DateTime
+}
+interface EntityUpdatedAt {
+    var updatedAt: DateTime
+}
+
+class EntityCreatedAtImp(
+    override val createdAt: DateTime = DateTime.now()
+) : EntityCreatedAt
+
+class EntityUpdatedAtImp(
+    override var updatedAt: DateTime = DateTime.now()
+) : EntityUpdatedAt
+
+/* Author */
+interface EntityCreatedBy<T : EntityI> {
+    val createdBy: T
+}
+interface EntityUpdatedBy<T : EntityI> {
+    var updatedBy: T
+}
+
+class EntityCreatedByImp<UserT : EntityI>(
+    override val createdBy: UserT
+) : EntityCreatedBy<UserT>
+
+class EntityUpdatedByImp<UserT : EntityI>(
+    override var updatedBy: UserT
+) : EntityUpdatedBy<UserT>
+
+/* Mixed */
+class EntityCreatedImp<UserT : EntityI>(
+    override val createdAt: DateTime = DateTime.now(),
+    createdBy: UserT
+) : EntityCreatedBy<UserT> by EntityCreatedByImp(createdBy),
+    EntityCreatedAt by EntityCreatedAtImp()
+
+class EntityUpdatedImp<UserT : EntityI>(
+    updatedAt: DateTime = DateTime.now(),
+    override var updatedBy: UserT
+) : EntityUpdatedBy<UserT>,
+    EntityUpdatedAt by EntityUpdatedAtImp(updatedAt)
+
+/* Implementation */
+abstract class EntityImp<T, UserT : EntityI>(
+    updatedBy: UserT,
+    updatedAt: DateTime = DateTime.now()
+) : UuidEntity(),
+    EntityCreatedAt by EntityCreatedAtImp(updatedAt),
+    EntityUpdatedAt by EntityUpdatedAtImp(updatedAt),
+    EntityDeletedAt by EntityDeletedAtImp(),
+    EntityCreatedBy<UserT> by EntityCreatedByImp(updatedBy),
+    EntityUpdatedBy<UserT> by EntityUpdatedByImp(updatedBy),
+    EntityDeletedBy<UserT> by EntityDeletedByImp(updatedBy)
\ No newline at end of file
diff --git a/src/main/kotlin/fr/postgresjson/entity/mutable/MutableEntity.kt b/src/main/kotlin/fr/postgresjson/entity/mutable/MutableEntity.kt
new file mode 100644
index 0000000..96f5145
--- /dev/null
+++ b/src/main/kotlin/fr/postgresjson/entity/mutable/MutableEntity.kt
@@ -0,0 +1,135 @@
+package fr.postgresjson.entity.mutable
+
+import fr.postgresjson.entity.EntityI
+import org.joda.time.DateTime
+import java.util.*
+
+interface EntityRefI<T> : EntityI {
+    var id: T?
+}
+
+interface UuidEntityI : EntityRefI<UUID> {
+    override var id: UUID?
+}
+
+interface IdEntityI : EntityRefI<Int> {
+    override var id: Int?
+}
+
+abstract class Entity<T>(override var id: T? = null) : EntityRefI<T>
+open class UuidEntity(override var id: UUID? = UUID.randomUUID()) : UuidEntityI, Entity<UUID>(id)
+open class IdEntity(override var id: Int? = null) : IdEntityI, Entity<Int>(id)
+
+/* Version */
+interface EntityVersioning<ID, NUMBER> {
+    var versionId: ID
+    var versionNumber: NUMBER?
+}
+
+class UuidEntityVersioning : EntityVersioning<UUID, Int> {
+    override var versionId: UUID = UUID.randomUUID()
+    override var versionNumber: Int? = null
+}
+
+/* Dates */
+interface EntityCreatedAt {
+    var createdAt: DateTime?
+}
+
+interface EntityUpdatedAt {
+    var updatedAt: DateTime?
+}
+
+interface EntityDeletedAt {
+    var deletedAt: DateTime?
+    fun isDeleted(): Boolean {
+        val deletedAt = deletedAt
+        return deletedAt != null && deletedAt < DateTime.now()
+    }
+}
+
+class EntityCreatedAtImp : EntityCreatedAt {
+    override var createdAt: DateTime? = null
+}
+
+class EntityUpdatedAtImp : EntityUpdatedAt {
+    override var updatedAt: DateTime? = null
+}
+
+class EntityDeletedAtImp : EntityDeletedAt {
+    override var deletedAt: DateTime? = null
+}
+
+/* Author */
+interface EntityCreatedBy<T : EntityI> {
+    var createdBy: T?
+}
+
+interface EntityUpdatedBy<T : EntityI> {
+    var updatedBy: T?
+}
+
+interface EntityDeletedBy<T : EntityI> {
+    var deletedBy: T?
+}
+
+class EntityCreatedByImp<UserT : EntityI>(
+    override var createdBy: UserT?
+) : EntityCreatedBy<UserT>
+
+class EntityUpdatedByImp<UserT : EntityI>(
+    override var updatedBy: UserT?
+) : EntityUpdatedBy<UserT>
+
+class EntityDeletedByImp<UserT : EntityI>(
+    override var deletedBy: UserT?
+) : EntityDeletedBy<UserT>
+
+/* Mixed */
+class EntityDeletedImp<UserT : EntityI>(
+    override var deletedBy: UserT? = null
+) : EntityDeletedBy<UserT>,
+    EntityDeletedAt by EntityDeletedAtImp()
+
+class EntityUpdatedImp<UserT : EntityI>(
+    override var updatedAt: DateTime? = null,
+    override var updatedBy: UserT? = null
+) : EntityUpdatedBy<UserT>,
+    EntityUpdatedAt by EntityUpdatedAtImp()
+
+class EntityCreatedImp<UserT : EntityI>(
+    override var createdAt: DateTime? = null,
+    override var createdBy: UserT? = null
+) : EntityCreatedBy<UserT>,
+    EntityCreatedAt by EntityCreatedAtImp()
+
+/* Published */
+interface Published<UserT : EntityI> {
+    var publishedAt: DateTime?
+    var publishedBy: UserT?
+}
+
+class EntityPublishedImp<UserT : EntityI>(
+    override var publishedBy: UserT?
+) : Published<UserT> {
+    override var publishedAt: DateTime? = null
+}
+
+/* Implementation */
+abstract class EntityImp<T, UserT : EntityI>(
+    updatedBy: UserT?
+) : Entity<T>(),
+    EntityCreatedAt by EntityCreatedAtImp(),
+    EntityUpdatedAt by EntityUpdatedAtImp(),
+    EntityDeletedAt by EntityDeletedAtImp(),
+    EntityCreatedBy<UserT> by EntityCreatedByImp(updatedBy),
+    EntityUpdatedBy<UserT> by EntityUpdatedByImp(updatedBy),
+    EntityDeletedBy<UserT> by EntityDeletedByImp(updatedBy)
+
+abstract class UuidEntityExtended<T, UserT : EntityI>(
+    updatedBy: UserT?,
+    publishedBy: UserT?
+) :
+    EntityImp<T, UserT>(updatedBy),
+    EntityVersioning<UUID, Int> by UuidEntityVersioning(),
+    Published<UserT> by EntityPublishedImp(publishedBy)
diff --git a/src/main/kotlin/fr/postgresjson/migration/Migrations.kt b/src/main/kotlin/fr/postgresjson/migration/Migrations.kt
index 1d13d62..54c3c5e 100644
--- a/src/main/kotlin/fr/postgresjson/migration/Migrations.kt
+++ b/src/main/kotlin/fr/postgresjson/migration/Migrations.kt
@@ -3,7 +3,7 @@ package fr.postgresjson.migration
 import com.fasterxml.jackson.core.type.TypeReference
 import fr.postgresjson.connexion.Connection
 import fr.postgresjson.definition.Function.FunctionNotFound
-import fr.postgresjson.entity.Entity
+import fr.postgresjson.entity.mutable.Entity
 import fr.postgresjson.migration.Migration.Action
 import fr.postgresjson.migration.Migration.Status
 import fr.postgresjson.utils.LoggerDelegate
diff --git a/src/main/kotlin/fr/postgresjson/migration/Query.kt b/src/main/kotlin/fr/postgresjson/migration/Query.kt
index 700a86a..ef43c88 100644
--- a/src/main/kotlin/fr/postgresjson/migration/Query.kt
+++ b/src/main/kotlin/fr/postgresjson/migration/Query.kt
@@ -1,7 +1,7 @@
 package fr.postgresjson.migration
 
 import fr.postgresjson.connexion.Connection
-import fr.postgresjson.entity.Entity
+import fr.postgresjson.entity.mutable.Entity
 import fr.postgresjson.migration.Migration.Action
 import java.util.*
 
diff --git a/src/test/kotlin/fr/postgresjson/ConnectionTest.kt b/src/test/kotlin/fr/postgresjson/ConnectionTest.kt
index e9cc617..d9be2fa 100644
--- a/src/test/kotlin/fr/postgresjson/ConnectionTest.kt
+++ b/src/test/kotlin/fr/postgresjson/ConnectionTest.kt
@@ -1,7 +1,7 @@
 package fr.postgresjson
 
 import fr.postgresjson.connexion.Paginated
-import fr.postgresjson.entity.IdEntity
+import fr.postgresjson.entity.mutable.IdEntity
 import fr.postgresjson.entity.Parameter
 import org.junit.Assert.*
 import org.junit.jupiter.api.Assertions
@@ -38,8 +38,7 @@ class ConnectionTest() : TestAbstract() {
         """.trimIndent()
         )
         assertNotNull(objs)
-        assertTrue(objs is List<ObjTest2>)
-        assertEquals(objs!!.size, 2)
+        assertEquals(objs.size, 2)
         assertEquals(objs[0].id, 1)
         assertEquals(objs[0].test!!.id, 1)
     }
diff --git a/src/test/kotlin/fr/postgresjson/EntityTest.kt b/src/test/kotlin/fr/postgresjson/EntityTest.kt
index 03cfc95..4452c4c 100644
--- a/src/test/kotlin/fr/postgresjson/EntityTest.kt
+++ b/src/test/kotlin/fr/postgresjson/EntityTest.kt
@@ -1,6 +1,7 @@
 package fr.postgresjson
 
-import fr.postgresjson.entity.*
+import fr.postgresjson.entity.EntityI
+import fr.postgresjson.entity.mutable.*
 import org.junit.jupiter.api.Assertions.assertTrue
 import org.junit.jupiter.api.Test
 import org.junit.jupiter.api.TestInstance
diff --git a/src/test/kotlin/fr/postgresjson/RequesterTest.kt b/src/test/kotlin/fr/postgresjson/RequesterTest.kt
index de72950..4ac074b 100644
--- a/src/test/kotlin/fr/postgresjson/RequesterTest.kt
+++ b/src/test/kotlin/fr/postgresjson/RequesterTest.kt
@@ -2,7 +2,7 @@ package fr.postgresjson
 
 import fr.postgresjson.connexion.Paginated
 import fr.postgresjson.connexion.Requester
-import fr.postgresjson.entity.IdEntity
+import fr.postgresjson.entity.mutable.IdEntity
 import org.junit.Assert
 import org.junit.jupiter.api.Assertions.assertEquals
 import org.junit.jupiter.api.Test
diff --git a/src/test/kotlin/fr/postgresjson/SerializerTest.kt b/src/test/kotlin/fr/postgresjson/SerializerTest.kt
index 9d9bd10..f222fb7 100644
--- a/src/test/kotlin/fr/postgresjson/SerializerTest.kt
+++ b/src/test/kotlin/fr/postgresjson/SerializerTest.kt
@@ -1,6 +1,6 @@
 package fr.postgresjson
 
-import fr.postgresjson.entity.IdEntity
+import fr.postgresjson.entity.mutable.IdEntity
 import fr.postgresjson.serializer.Serializer
 import fr.postgresjson.serializer.deserialize
 import fr.postgresjson.serializer.serialize