Containment
Membership is usually shown by nesting. When it is clearer to draw a line, owner +-- member puts a
circle-plus on the owner. Members in the next rank share one trunk.
diagram package "Containment"
package Types
class Shape
class Point
Types +-- Shape
Types +-- Point
Syntax
owner +-- member
member --+ owner
Use it for members declared outside the owner’s block. A member drawn inside its owner needs no line, so
+-- to it is an error.
Specification
UML 2.5.1, 12.2.4 (p. 248).