diff --git a/WD7UVN_HFT_2023241.Models/Customer.cs b/WD7UVN_HFT_2023241.Models/Customer.cs
index e50b5cf..a2f6bf9 100644
--- a/WD7UVN_HFT_2023241.Models/Customer.cs
+++ b/WD7UVN_HFT_2023241.Models/Customer.cs
@@ -1,17 +1,25 @@
 using System;
 using System.Collections.Generic;
+using System.ComponentModel.DataAnnotations;
+using System.ComponentModel.DataAnnotations.Schema;
 using System.Linq;
 using System.Text;
 using System.Threading.Tasks;
 
 namespace WD7UVN_HFT_2023241.Models
 {
-    internal class Customer
+    public class Customer
     {
+        [Key]
         public int ID { get; set; }
+        [Required]
+        [StringLength(240)]
         public string NAME { get; set; }
+        [StringLength(240)]
         public string EMAIL { get; set; }
+        [StringLength(240)]
         public string PHONE { get; set; }
+        [ForeignKey(nameof(Service))]
         public int SERVICE_ID { get; set; }
     }
 }
diff --git a/WD7UVN_HFT_2023241.Models/Employee.cs b/WD7UVN_HFT_2023241.Models/Employee.cs
index 9bb0df4..169888e 100644
--- a/WD7UVN_HFT_2023241.Models/Employee.cs
+++ b/WD7UVN_HFT_2023241.Models/Employee.cs
@@ -1,18 +1,27 @@
 using System;
 using System.Collections.Generic;
+using System.ComponentModel.DataAnnotations;
+using System.ComponentModel.DataAnnotations.Schema;
 using System.Linq;
 using System.Text;
 using System.Threading.Tasks;
 
 namespace WD7UVN_HFT_2023241.Models
 {
-    internal class Employee
+    public class Employee
     {
+        [Key]
         public int ID { get; set; }
+        [Required]
+        [StringLength(240)]
         public string NAME { get; set; }
+        [StringLength(240)]
         public string EMAIL { get; set; }
+        [StringLength(240)]
         public string PHONE { get; set; }
+        [ForeignKey(nameof(MaintainerTeam))]
         public int MAINTAINER_ID { get; set; }
+        [ForeignKey(nameof(Employee))]
         public int MANAGER { get; set; }
     }
 }
diff --git a/WD7UVN_HFT_2023241.Models/MaintainerTeam.cs b/WD7UVN_HFT_2023241.Models/MaintainerTeam.cs
index 34786f8..ea180df 100644
--- a/WD7UVN_HFT_2023241.Models/MaintainerTeam.cs
+++ b/WD7UVN_HFT_2023241.Models/MaintainerTeam.cs
@@ -1,12 +1,20 @@
 using System;
+using System.ComponentModel.DataAnnotations;
+using System.ComponentModel.DataAnnotations.Schema;
 
 namespace WD7UVN_HFT_2023241.Models
 {
     public class MaintainerTeam
     {
+        [Key]
         public int ID {  get; set; }
+        [Required]
+        [StringLength(240)]
         public string NAME { get; set; }
+        [StringLength(240)]
         public string EMAIL { get; set; }
+        [Required]
+        [ForeignKey(nameof(Employee))]
         public int LEADER_EMPLOYEE_ID { get; set; }
     }
 }
diff --git a/WD7UVN_HFT_2023241.Models/Service.cs b/WD7UVN_HFT_2023241.Models/Service.cs
index f61d5ed..e788fbb 100644
--- a/WD7UVN_HFT_2023241.Models/Service.cs
+++ b/WD7UVN_HFT_2023241.Models/Service.cs
@@ -1,15 +1,27 @@
-namespace WD7UVN_HFT_2023241.Models
+using System.ComponentModel.DataAnnotations;
+using System.ComponentModel.DataAnnotations.Schema;
+
+namespace WD7UVN_HFT_2023241.Models
 {
-    internal class Service
+    public class Service
     {
+        [Key]
         public int ID { get; set; }
+        [ForeignKey(nameof(MaintainerTeam))]
+        [Required]
         public int MAINTAINER { get; set; }
+        [Required]
         public string NAME { get; set; }
-        public int? VERSION { get; set; }
-        public string? ACCOUNT { get; set; }
-        public string? NOTES { get; set; }
-        public string? SERVICE_DOMAIN { get; set; }
-        public string? IP { get; set; }
-        public int? PORT { get; set; }
+        public int VERSION { get; set; }
+        [StringLength(240)]
+        public string ACCOUNT { get; set; }
+        [StringLength(240)]
+        public string NOTES { get; set; }
+        [StringLength(240)]
+        public string SERVICE_DOMAIN { get; set; }
+        [StringLength(240)]
+        public string IP { get; set; }
+        [StringLength(240)]
+        public int PORT { get; set; }
     }
 }