1. 2/9/98 Thomas O’Reilly 1 A Quick UML Introduction

2. 2/9/98 Thomas O’Reilly 2 What is UML and why use it?  Unified Modeling Language  UML is a way of visualising models We are interested in class diagrams. Class diagrams work with classes and the relationships between them  UML is an industry standard  UML is already used by many people in LHCb It may become standard for LHCb  UML is the default method in Rational Rose Rational Rose can turn UML diagrams into C++ code

3. 2/9/98 Thomas O’Reilly 3 Classes Name of the class Attributes of the class (data members) Operations of the class (member functions)

4. 2/9/98 Thomas O’Reilly 4 Inheritance  The arrow symbol is used to show derived types  Dog and Cat are both subclasses of Mammal They inherit from the class Mammal  Key phrase “A dog ‘is a kind of’ Mammal”  The code equivalent is class Dog : public Mammal{... }

5. 2/9/98 Thomas O’Reilly 5 Aggregation  This black diamond symbol is used to show that an object of type Car will contain an object of type Engine code equivalent class car{ private: Engine engine  Key phrase “car ‘has an’ engine”  The name of the object contained is the name on the arrow (engine) The negative sign before engine means private containment + public # protected - private  The numbers show cardinality

6. 2/9/98 Thomas O’Reilly 6 More Aggregation  The empty diamond means that a reference to the object will be contained  An object of type Person will contain the address of objects of type Cat and Dog (or NULL pointers) code equivalent class person{ private: Cat *MyCat Dog *MyDog  Numbers show cardinality

7. 2/9/98 Thomas O’Reilly 7 Cardinality  The numbers on the ends of relationship arrows show cardinality  Cardinality is the number of objects of that type that your object will be associated with  A person may have no dog or one dog only. A dog however has to have exactly one owner  A person may own as many fish as he likes The fish will be held in a container ( for LHCb : STL vector )

8. 2/9/98 Thomas O’Reilly 8 Dependency (Use Relationship)  Drawn as a dotted arrow  Used when one class may require the services of another  In this example the Printer knows about the class Formatter so that it can use its services