From 352a3acf7655b39b6da0ee50764e6aa02cfc6bf7 Mon Sep 17 00:00:00 2001
From: mo khan <mo.khan@gmail.com>
Date: Mon, 6 Jan 2020 19:46:54 -0700
Subject: Add example of unary relationship

---
 assignments/1/README.md              |   7 +++++++
 assignments/1/unary-relationship.png | Bin 0 -> 5601 bytes
 assignments/1/unary-relationship.uml |  17 +++++++++++++++++
 3 files changed, 24 insertions(+)
 create mode 100644 assignments/1/unary-relationship.png
 create mode 100644 assignments/1/unary-relationship.uml

diff --git a/assignments/1/README.md b/assignments/1/README.md
index a91c1e5..bb05688 100644
--- a/assignments/1/README.md
+++ b/assignments/1/README.md
@@ -63,6 +63,13 @@ b. Weak entity
 
 c. Unary relationship
 
+  A unary relationship is a relationship between the instances of a single entity type.
+  This is a self referential or recursive relationship.
+
+  Group is subgroup of group.
+
+  ![unary relationship example](./unary-relationship.png)
+
 ### Question 3 (20 marks)
 
 As an independent consultant, you have a contract with Athabasca University to develop an application to support
diff --git a/assignments/1/unary-relationship.png b/assignments/1/unary-relationship.png
new file mode 100644
index 0000000..a2d7ecb
Binary files /dev/null and b/assignments/1/unary-relationship.png differ
diff --git a/assignments/1/unary-relationship.uml b/assignments/1/unary-relationship.uml
new file mode 100644
index 0000000..91c0425
--- /dev/null
+++ b/assignments/1/unary-relationship.uml
@@ -0,0 +1,17 @@
+@startuml
+!define Table(name,desc) class name as "desc" << (T,#FFAAAA) >>
+!define primary_key(x) <b>x</b>
+!define unique(x) <color:green>x</color>
+!define not_null(x) <u>x</u>
+hide methods
+hide stereotypes
+
+' entities
+Table(group, "group") {
+  primary_key(id) INTEGER
+  not_null(name) VARCHAR[255]
+}
+
+' relationships
+group --> group : "A group may be a sub group of another group"
+@enduml
-- 
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