Index: sql/iknow.dbml
===================================================================
--- sql/iknow.dbml	(revision 1a9c843acf41686a27bf5c58dc77ace2cf638132)
+++ sql/iknow.dbml	(revision bcacc91b5770933c5f080d279be105c850b2ece9)
@@ -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