Software System Engineering

1. Software System Engineering Dr. M.E. Fayad, Professor Computer Engineering Department, Room #283I College of Engineering San José State University One Washington Square San José, CA 95192-0180 http://www.engr.sjsu.edu/~fayad SJSU -- CmpE

2. Lesson 15: Relationships 2 SJSU -- CmpE M.E. Fayad

3. Lesson Objectives • Discuss UML Associations • Discuss UML – aggregation • Understand UML- inheritance • Understand How to identify UML Artifacts 3 SJSU -- CmpE M.E. Fayad

4. A relationship is a connection among things Three most important relationships in OO dependencies generalizations associations Different kind of lines are used to distinguish various kinds of relationships Relationships 4 SJSU -- CmpE M.E. Fayad

5. Dependencies are using relationships State that a change in specification of one thing (the supplier) may affect another thing that uses it (the client), but not necessary the reverse Graphically, it is rendered as a dashed directed line Dependencies (1) 5 SJSU -- CmpE M.E. Fayad

6. Dependencies (2) Dependent Class Independent Class Client Supplier 6 Order Book SJSU -- CmpE M.E. Fayad

7. An association shows a two-way relationship between objects (instances) of two or more classes and requiring special implementation to ensure integrity. A particular instance of an association is often called a link. Associations between classes are required if the objects need to communicate. Associations are often named, and have role-names for each side of the link. Associations (1) 7 SJSU -- CmpE M.E. Fayad

8. Unary association both ends of an association circle back to the same class Binary association an association that connects exactly two classes N-ary association an association that connects more than two classes Types of Association 8 SJSU -- CmpE M.E. Fayad

9. Name an association can have a name, and the name is used to describe the nature of the relationship Role when a class participates in an association, it has a specific role that it plays in that relationship a role is just the face the class at the near end of the association presents to the class at the other end of the association Associations (2) 9 SJSU -- CmpE M.E. Fayad

10. Associations (3) Association Name Car Person Vehicle Registration model year # of doors name age address registeredCar owner Roles Names 10 SJSU -- CmpE M.E. Fayad

11. Associations (4) Multiplicity Name Owns by 1..* * Person Company employer employee 11 Role Name SJSU -- CmpE M.E. Fayad

12. Simple example: An association has a name and a numerical specification (multiplicity indication) of how many objects on one side of the association are connected with how many objects on the other side. Associations are called use relationships – even if this may seem somewhat cheeky in the example below More on Associations displays 0..* Window GeomFigure employs 0..* Company Person 12 Employer Employee SJSU -- CmpE M.E. Fayad

13. Associations are directed (one way), bidirectional, and undirected. UML makes no distinction between bidirectional and undirected associations. More on Associations Multiplicity Stereotype RelationName {Constraints} * Class1 Class2 13 role1 Role2: interface SJSU -- CmpE M.E. Fayad

14. Recursive association: A class has a relation with itself. It is also possible to model associations that are valid only temporarily “stereotype or temporary” Constraints may be used to restrict the relation under specific aspects. A role name describes how the object is seen by the opposite object in the association. An association can be described in more detail by means of constraints, tagged values, and stereotypes. Stereotypes are noted before or above the relation name, constraints, and tagged values after or below the name. More on Associations 14 SJSU -- CmpE M.E. Fayad

15. Directed association is a one-way association, in which one side knows the other, but not vice versa. Multiplicity Specification: 1 exactly one 0, 1 zero or one 0..4 between zero and four 3, 7 either three or seven More on Associations 15 SJSU -- CmpE M.E. Fayad

16. More multiplicity specifications: 0..* greater than or equal to zero (default) * ditto 1..* greater than or equal to one 0..3, 7, 9..* between zero and three, or exactly seven, or greater than or equal to nine. More on Associations 16 SJSU -- CmpE M.E. Fayad

17. Multiplicity how many objects may be connected across an instance of an association can be a range of values or an explicit value exactly one 1 zero or one (optional) 0..1 zero or more (many) 0..* one or more (mandatory) 1..* numerically specified m..n More Multiplicities 17 SJSU -- CmpE M.E. Fayad

18. Recursive associations are associations in which one class is involved. More on Associations has Patient Employee name staffNo roomNo office clerk relative * * 1 manager Person leads 18 reports to SJSU -- CmpE M.E. Fayad

19. An n-ary association is like a common (binary) association, except that more than two association roles involved in it. N-ary Association N-ary association Class1 Class2 Ternary association 19 Class3 SJSU -- CmpE M.E. Fayad

20. More on n-ary Association Reservation Seat Train 1..* 1 carriageNo seatNo date trainNo 1..* Passenger name title Ternary association 20 SJSU -- CmpE M.E. Fayad

21. More on Associations • Recursive Associations • N-ary Associations • Attributed Associations (Association Class) • Association Constraints • Qualified Associations • Derived Associations • Directed Associations • Ordered Associations • Realization/Refinements • Dependency 21 SJSU -- CmpE M.E. Fayad

22. More on Associations • Associations are usually bidirectional • Allows each object involved in the relationship to refer to the object to which it is related. • Bidirectional association means at the relationship has an inverse. • Associations do not have to be bidirectional. 22 SJSU -- CmpE M.E. Fayad

23. Association Type One-to-One One-to-Many (One-to-Zero-or-More) Many-to-Many Zero or One Man Woman Marriage husband wife Screen Window Windows Nets User Authorization Car Trailer 23 SJSU -- CmpE M.E. Fayad

24. Association Type Specified the # of instances on the “many” side Specify the possible # of instances using “or” Ternary relationship Square Line Sides Secure Room Person Occupants TraditionalFamily Male Female • father mother • children 24 Child SJSU -- CmpE M.E. Fayad

25. Association Class Server Client Connection Connection baudRate protocol wireType disconnect rerouteLink • These attributes don’t belong in either the Client or Server class. • They are attributes of the connection itself. 25 • The association class can have behaviors as well as attributes. SJSU -- CmpE M.E. Fayad

26. Aggregation is a special form of association. Aggregation is used when the relationship is “part/whole” or “contains/is-part-of” Aggregation is transitive and operations on “whole” often cascade down to “parts”. Aggregation & Composite 26 SJSU -- CmpE M.E. Fayad

27. Aggregation & Composite Computer Server Aggregation “whole” “part” 52 * CPU Disk Drive Client Keyboard Mouse 27 SJSU -- CmpE M.E. Fayad

28. Special diamond symbol used on “whole” side to indicate aggregation. Aggregation is an anti-symmetric that is, if A is part of B, then B is not part of A. DO NOT confuse aggregation with generalization An essential property of aggregates is that the whole acts as a proxy for its parts. A composition is a strict form of aggregation, in which the parts are existence-dependent on the entirely Aggregation & Composite 28 SJSU -- CmpE M.E. Fayad

29. Aggregation Whole Car Anywhere from four to many 1 1 1 1 4..* 1 Body Motor Wheel 29 Part SJSU -- CmpE M.E. Fayad

30. Aggregation & Composite Aggregation Part Entirely Composition Existence- DependentPart 30 SJSU -- CmpE M.E. Fayad

31. Mr. Clinton’s hand is part-of Mr. Clinton & Mr. Clinton is part-of U.S.A. Therefore: Mr. Clinton’s hand is part-of U.S.A. Aggregation Problem 31 SJSU -- CmpE M.E. Fayad

32. Keypad Cash Register Example * Total Key Subtotal Key Number Keys display display display drawer Drawer Display 32 SJSU -- CmpE M.E. Fayad

33. Attributes are simply the information associated with the object. The data type used to hold the attributes is often a fundamental type, such as int or char. Sometimes the attribute can be a non-fundamental type, such as String type and Address type. Avoid using attributes which might be better implemented as an association to a new class. Attributes 33 SJSU -- CmpE M.E. Fayad

34. x More on Attributes • For example: Using Association Using Attributes TV TV Manufacturer String model String serialNum String manName String model String serialNum • product manu- • facturer String name Address address * • Why? Using an association to a Manufacturer class, the name and address of each manufacturer will be stored in one place rather than in each of the TV objects made by that manufacturer. 34 SJSU -- CmpE M.E. Fayad

35. More on Attributes • If attributes only make sense in some instances of a given class but not in others. It will make sense to split the single class into two classes or more. Employee String name float salary Employee Split into two classes String name float salary long clearanceNum inheritance ClearedEmployee 35 long clearanceNum openVault() • Not all employees have clearances SJSU -- CmpE M.E. Fayad

36. A relationship between a general thing (called the superclass or parent) and a more specific kind of that thing (called the subclass or child) also known as the “is-a-kind-of” relationship A child is substitutable for the parent inherits the properties of its parents Generalization (1) 36 SJSU -- CmpE M.E. Fayad

37. A class may have zero, one, or more parents that has no parents and has one or more children is called a root class or a base class that has no children is called a leaf class Inheritance a class with exactly one parent uses single inheritance a class with more than one parent uses multiple inheritance Graphically, it is rendered as a solid directed line with a large open arrowhead, pointing to the parent Generalization (2) 37 SJSU -- CmpE M.E. Fayad

38. When a relationship exists between classes such that lower-level classes (called subclasses) share certain attributes and behaviors which can be defined once in a higher-level class (called superclasses). Subclasses inherit properties (attributes and behaviors) of its superclass and then adds its own unique properties and modifies any inherited properties. This is called Generalization or Inheritance. Inheritance 38 SJSU -- CmpE M.E. Fayad

39. Leaf Class Base and Leaf Classes Base Class Account Bank book Checking Loan 39 SJSU -- CmpE M.E. Fayad

40. More on Inheritance Window paintWindow size icon bitmaps textWindow contents 40 SJSU -- CmpE M.E. Fayad

41. Passenger Car Account Bank book Checking Loan Taxi Private Car Single inheritance Service Single and Multiple Inheritance Multiple inheritance 41 SJSU -- CmpE M.E. Fayad

42. Aggregation vs. Inheritance AggregationInheritance Instances of distinct classes Instances of a single class “a-part-of” (APO) “a-kind-of” or “is-a” (AKO) Contains superclass-of Aggregate + parts Superclass + subclass “and” relationship “or” relationship Propagated only if specified Inheritance 42 SJSU -- CmpE M.E. Fayad

43. What are the other terms for attributes & operations? Define an object and a class in UML What is an association? Give examples Associations are usually bidirectional. Please describe. Describe the basic difference between aggregation and inheritance. What do they have in common? What do you think “multiple inheritance” means? Which type of association is more likely to yield savings in the amount of code required for implementation? why? Define the process of identifying objects, classes, inheritance, associations & aggregation, attributes, and behaviors Define Polymorphism with examples What do we mean by saying “Model/View/Controller”? Discussion Questions 43 SJSU -- CmpE M.E. Fayad