Diagram types and short description of each:

Type	Relation	Implementation	UML
Association	knows a	Contains a pointer or reference to another object.
		Undirected usually means: It has not been decided whether the association is directed or the association is bidirectional (can call each other).
Dependency	uses (temporarily) a	The independent class is a parameter variable or a local variable of a method of the dependent class.
Aggregation	has a	A class is a collection or container of other classes. The contained classes do not have a strong life cycle dependency on the container(-class) -> if the container is destroyed, its contents are not.
	is entirely made of	Association differs from aggregation only in that it does not imply any containment.
Composition	has a	= stronger form of aggregation. If the container is destroyed, its contents are also destroyed.
Inheritance	is a	A class is derived from another class.
Class template	is a	Template classes mean generic classes.

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• void return type can be omitted
• Arrows are sometimes optional like in aggregation, composition, ...
  • The worded relation refers to the direction the arrow would go (A --> B; A knows a B)
• Relationship grouping
  • Association
    • Dependency
    • Aggregation
    • Composition
  • Generalisation
    • Inheritance
    • Template class
    • Interface

• multiplicity
  • *: 0, 1, or more
  • 1: exactly this number
  • 4..8: range (inclusive)
  • 5..*: range (5 or more)

Object (here: BrokenPencil) of a certain class (here: Junk):

See BrokenPencil as an instance of Junk.

Possibilities via:

1. decision node
2. loop block

• Activity diagrams - good and detailed overview
• Allen Holub’s UML Quick Reference - good overview
• Design and UML Class Diagrams
• UML Class Diagram Explained With C++ samples