Index: iknow-api/Services/Interfaces/IEnrollmentService.cs
===================================================================
--- iknow-api/Services/Interfaces/IEnrollmentService.cs	(revision ea405569ef29f56fbfc4d77708b6b3faf9286097)
+++ iknow-api/Services/Interfaces/IEnrollmentService.cs	(revision ea405569ef29f56fbfc4d77708b6b3faf9286097)
@@ -0,0 +1,16 @@
+using iknow_api.DTOs;
+
+namespace iknow_api.Services
+{
+    public interface IEnrollmentService
+    {
+        /// <summary>The semesters, majors and subjects this student may enrol in.</summary>
+        Task<EnrollmentOptionsDto> GetOptionsAsync(int studentId);
+
+        /// <summary>
+        /// Creates one enrolled_semesters row and its semesters_subjects rows,
+        /// or returns why it could not.
+        /// </summary>
+        Task<EnrollSemesterResultDto> EnrollAsync(int studentId, EnrollSemesterRequestDto request);
+    }
+}