diff --git a/TheCyclopsProject/TheCyclopsContracts/BusinessLogicContracts/IComponentBusinessLogicContract.cs b/TheCyclopsProject/TheCyclopsContracts/BusinessLogicContracts/IComponentBusinessLogicContract.cs
new file mode 100644
index 0000000..aef646a
--- /dev/null
+++ b/TheCyclopsProject/TheCyclopsContracts/BusinessLogicContracts/IComponentBusinessLogicContract.cs
@@ -0,0 +1,16 @@
+using TheCyclopsContracts.DataModels;
+
+namespace TheCyclopsContracts.BusinessLogicContracts;
+
+public interface IComponentBusinessLogicContract
+{
+    List<ComponentDataModel> GetAllComponents(bool onlyActive = true);
+
+    ComponentDataModel GetComponentByData(string data);
+
+    void InsertComponent(ComponentDataModel componentDataModel);
+
+    void UpdateComponent(ComponentDataModel componentDataModel);
+
+    void DeleteComponent(string id);
+}
diff --git a/TheCyclopsProject/TheCyclopsContracts/BusinessLogicContracts/IEmployeeBusinessLogicContract.cs b/TheCyclopsProject/TheCyclopsContracts/BusinessLogicContracts/IEmployeeBusinessLogicContract.cs
new file mode 100644
index 0000000..aed6028
--- /dev/null
+++ b/TheCyclopsProject/TheCyclopsContracts/BusinessLogicContracts/IEmployeeBusinessLogicContract.cs
@@ -0,0 +1,24 @@
+using TheCyclopsContracts.DataModels;
+
+namespace TheCyclopsContracts.BusinessLogicContracts;
+
+public interface IEmployeeBusinessLogicContract
+{
+    List<EmployeeDataModel> GetAllEmployees(bool onlyActive = true);
+
+    List<EmployeeDataModel> GetAllEmployeesByPost(string postId, bool onlyActive = true);
+
+    List<EmployeeDataModel> GetAllEmployeesByBirthDate(DateTime fromDate, DateTime toDate, 
+        bool onlyActive = true);
+
+    List<EmployeeDataModel> GetAllEmployeesByEmploymentDate(DateTime fromDate, DateTime toDate, 
+        bool onlyActive = true);
+
+    EmployeeDataModel GetEmployeeByData(string data);
+
+    void InsertEmployee(EmployeeDataModel employeeDataModel);
+
+    void UpdateEmployee(EmployeeDataModel employeeDataModel);
+
+    void DeleteEmployee(string id);
+}
diff --git a/TheCyclopsProject/TheCyclopsContracts/BusinessLogicContracts/IInstallationBusinessLogicContract.cs b/TheCyclopsProject/TheCyclopsContracts/BusinessLogicContracts/IInstallationBusinessLogicContract.cs
new file mode 100644
index 0000000..57305e6
--- /dev/null
+++ b/TheCyclopsProject/TheCyclopsContracts/BusinessLogicContracts/IInstallationBusinessLogicContract.cs
@@ -0,0 +1,20 @@
+using TheCyclopsContracts.DataModels;
+
+namespace TheCyclopsContracts.BusinessLogicContracts;
+
+public interface IInstallationBusinessLogicContract
+{
+    List<InstallationDataModel> GetAllInstallationsByPeriod(DateTime fromDate, DateTime toDate);
+
+    List<InstallationDataModel> GetAllInstallationsByEmployeeByPeriod(string employeeId, 
+        DateTime fromDate, DateTime toDate);
+
+    List<InstallationDataModel> GetAllInstallationsByComponentByPeriod(string componentId, 
+        DateTime fromDate, DateTime toDate);
+
+    InstallationDataModel GetInstallationByData(string data);
+
+    void InsertInstallation(InstallationDataModel installationDataModel);
+
+    void CancelInstallation(string id);
+}
diff --git a/TheCyclopsProject/TheCyclopsContracts/BusinessLogicContracts/IPostBusinessLogicContract.cs b/TheCyclopsProject/TheCyclopsContracts/BusinessLogicContracts/IPostBusinessLogicContract.cs
new file mode 100644
index 0000000..5cbdc5f
--- /dev/null
+++ b/TheCyclopsProject/TheCyclopsContracts/BusinessLogicContracts/IPostBusinessLogicContract.cs
@@ -0,0 +1,20 @@
+using TheCyclopsContracts.DataModels;
+
+namespace TheCyclopsContracts.BusinessLogicContracts;
+
+public interface IPostBusinessLogicContract
+{
+    List<PostDataModel> GetAllPosts(bool onlyActive);
+
+    List<PostDataModel> GetAllDataOfPost(string postId);
+
+    PostDataModel GetPostByData(string data);
+
+    void InsertPost(PostDataModel postDataModel);
+
+    void UpdatePost(PostDataModel postDataModel);
+
+    void DeletePost(string id);
+
+    void RestorePost(string id);
+}
diff --git a/TheCyclopsProject/TheCyclopsContracts/BusinessLogicContracts/ISalaryBusinessLogicContract.cs b/TheCyclopsProject/TheCyclopsContracts/BusinessLogicContracts/ISalaryBusinessLogicContract.cs
new file mode 100644
index 0000000..98cc044
--- /dev/null
+++ b/TheCyclopsProject/TheCyclopsContracts/BusinessLogicContracts/ISalaryBusinessLogicContract.cs
@@ -0,0 +1,13 @@
+using TheCyclopsContracts.DataModels;
+
+namespace TheCyclopsContracts.BusinessLogicContracts;
+
+public interface ISalaryBusinessLogicContract
+{
+    List<SalaryDataModel> GetAllSalariesByPeriod(DateTime fromDate, DateTime toDate);
+
+    List<SalaryDataModel> GetAllSalariesByPeriodByEmployee(DateTime fromDate, DateTime toDate, 
+        string employeeId);
+
+    void CalculateSalaryByMounth(DateTime date);
+}