Index: sql/iknow.dbml
===================================================================
--- sql/iknow.dbml	(revision e7bafc08ad74099b6daf91b8414b90e3c4968111)
+++ sql/iknow.dbml	(revision 002cf5f9fe36565e030e882d63222c760d638995)
@@ -150,4 +150,5 @@
 Table project.payment {
   id integer [pk, increment]
+  user_id integer [not null]
   enrollment_id integer [not null]
   amount integer [not null]
@@ -187,4 +188,5 @@
 Ref: project.contact.user_id - project.users.id                      // has_contact (1:1)
 Ref: project.token.user_id > project.users.id                        // has_token
+Ref: project.payment.user_id > project.users.id                      // pays
 Ref: project.payment.enrollment_id > project.enrolled_semesters.id   // for_enrollment
 Ref: project.enrolled_semesters.user_id > project.users.id           // submits