1. Object-Oriented Modeling: Static Models Grady Booch, James Rumbaugh, and Ivar Jacobson, The Unified Modeling Language User Guide, 2 nd edition, Addison Wesley, 2005.

2. 2 Object-Oriented Modeling Using object-orientation as a base, model the system as a number of objects that interact. Our surroundings consist of objects, such as people, trees, cars, towns and houses which are in some way related to each other. A model which is designed using an O-O technology is often easy to understand, as it can be directly related to reality. No "semantic gap"

3. 3 Key Object-Oriented Ideas Identity Abstraction Classification Encapsulation Inheritance Polymorphism Persistence

4. 4 Key Object-Oriented Ideas Identity –Data are organized into discrete entities called objects. –Objects have behavior and state. Abstraction Classification Encapsulation Inheritance Polymorphism Persistence

5. 5 Key Object-Oriented Ideas Identity Abstraction –OO design uses different abstractions to capture different parts of the system. Classification Encapsulation Inheritance Polymorphism Persistence

6. 6 Key Object-Oriented Ideas Identity Abstraction Classification –Objects are grouped together by commonalities. –Groups of objects become the basis of classes. Encapsulation Inheritance Polymorphism Persistence

7. 7 Key Object-Oriented Ideas Identity Abstraction Classification Encapsulation –Classes encapsulate behavior and data. –Encapsulated aspects of classes hide details from other classes. Inheritance Polymorphism Persistence

8. 8 Key Object-Oriented Ideas Identity Abstraction Classification Encapsulation Inheritance –Different OO objects can reuse common behaviors through inheritance. Polymorphism Persistence

9. 9 Key Object-Oriented Ideas Identity Abstraction Classification Encapsulation Inheritance Polymorphism –Objects inherit types from parent classes as well as behavior Persistence

10. 10 Key Object-Oriented Ideas Identity Abstraction Classification Encapsulation Inheritance Polymorphism Persistence –Objects have lifetime. –Attributes of an object may change over its lifetime.

11. 11 Advantages of O-O Approach Shifting of development effort into analysis. –Some development effort is moved to the analysis phase. Emphasis on data before function. Seamless development process. –Models developed during analysis are used for design and implementation. The work is progressively refined rather than converting from one representation to another. Iterative rather than sequential. –Each iteration adds or clarifies features rather than modifies work that has already been done.

12. 12 OO Analysis Objective To develop precise, concise, understandable, and correct models of the problem context.

13. 13 Object Modeling Involves systems analysis and design based on three different views of the system: –Object Models –Dynamic Models –Functional Models

14. 14 Activities and Products of OOA 0. State the requirements 1. Build an Object Model 2. Develop a Dynamic Model 3. Construct a Functional Model 4. Verify, iterate, and refine the three models

15. 15 1. Build an Object Model Identify objects and classes Identify associations between objects Identify attributes of objects and associations Organize and simplify object classes using inheritance Verify that access paths exist for likely queries

16. 16 2. Develop a Dynamic Model Prepare scenarios of typical interaction sequences Identify Events between objects and prepare an event trace Build a state diagram, sequence diagram, or communication diagram Match events between objects to verify consistency

17. 17 3. Construct a Functional Model Identify Input and Output Values Build Use Case scenarios Build Data Flow Diagrams showing functional dependencies Describe Functions Identify Constraints Specify Optimization Criteria

18. 18 Three Orthogonal Models Object model (class diagram) –specifies static structure of objects and their relationships –specifies what objects a system contains Dynamic model (state diagrams) –specifies aspects of a system that change over time (when objects change) Functional model (data flow diagrams) –specifies data value transformations in a system (how objects change)

19. 19 Object Model --- Objects An Object is –A real world entity –Related to the problem domain –With crisply defined boundaries –Encapsulated along with its attributes and behaviors –Whose behavior and attributes must be understood in order to understand the problem.

20. 20 Examples Objects usually correspond to nouns in a "natural" language. Objects may represent physical entities (such as companies, people, lumber, I/O devices, etc.), concepts (such as "business process", "data analysis", etc.), and everything in between. Examples of objects include: IBM, Juan Mendoza, a 2’ 2x4, the ZIP drive, the interview protocol, and zero- crossing analysis.

21. 21 Classes A class is a "template" describing a set of objects with –similar properties (attributes), –common behavior (operations), –common relationships to other objects, and –common semantics.

22. 22 Instances An instance of a class is an object created at runtime based on a class (template). Sometimes class and object are used to mean the same thing (by mistake). An instance is used to refer to exactly one thing.

23. 23 Terminology Class: –A category –A type –A set Instance (of a class) –Something in the category, is of the type, or an element of the set –Object

24. 24 How to Recognize Objects Tangible things –These are the easier to find. They correspond to physical things: airplane, vehicle, book Roles played by persons or organizations –Example: patient, employee, client, etc. Incidents –Used to represent an occurrence or event: something which happens at a specific time. Example: flight, accident, performance, etc.

25. 25 More objects Interactions –A "transaction" or "contract", and relate to two or more other objects in the model. –Examples are: Purchase (related to buyer, seller, and thing purchased). Marriage (related to man and woman) Specifications –A standard or a definition. For example: a refrigerator model, the specification of what it means to be a certain model can be an object.

26. 26 Attributes Abstraction of a single characteristic possessed by all the instances of a class. –May corresponds to an adjective or possessive phrase in a natural language. –It is any property, quality, characteristic that can be assigned to an object. –E.g., color, size, name,...

27. 27 Good Attributes complete: includes all the information pertaining an object factorized. Each attribute captures one separated aspect of the objects' abstraction mutually independent. The attributes take on their values independently of one another

28. 28 How to Recognize Attributes Descriptive attributes. –Provide facts intrinsic to each instance of an object. –E.g., length, width Naming attributes. –Provide facts about the arbitrary labels and names carried by each instance of an object. –E.g., user-name, part-number Referential attributes. –Capture the facts that tie an instance of one object to an instance of another object. –E.g., is-controlled-by, is-driven-by

29. 29 Operations and Methods Behavior of objects is realized via operations. –A function or transformation that may be applied to objects in a class. by objects in a class –All objects in a class share the same operations. Method: the implementation of an operation. Operations usually correspond to verbs in a natural language (print, open, transform, mail)

30. 30 Recognizing Operations Manipulate data –add, delete, format, select, access. Perform a calculation –The calculation is performed according to the value of the attributes of the object student. Monitor the object to verify the occurrence of an event that is controlling the object. –Think about monitoring an object needs to do to respond to an external change. Verify the time continually to activate a process at exactly 12:00 Hrs.

31. 31 In Class Pairs (2 minutes): create a class list with attributes and operations: A student may take up to five courses in a semester. Each course may have as many as 30 students in each section. Each course has one section per semester. A class room can hold at most one course at a time.

32. 32 UML Class Diagram --- Notation for Classes Class Name Attributes Operations These may be abstract or at the source code level

33. 33 Attributes and Operations Car speed direction Level of detail varies with level of abstraction: start with high abstraction

34. 34 Attributes and Operations Car speed direction Refine with Types Car speed: Integer direction: Tuple

35. 35 Attributes and Operations Car speed direction Refine with Types Visibility Defaults Properties Car speed: Integer direction: Tuple 35 Car +speed: Integer = 0 +direction: Tuple {readOnly}

36. 36 Attributes and Operations Refine with Types Visibility Defaults Properties 36 Car +speed: Integer = 0 +direction: Tuple {readOnly} Visibility is “+” for public, “-” for private, # for protected, ~ for package Types correspond to the types from an implementation language Default is attribute=value Property string is {} with one or more of readOnly, ordered, sequence

37. 37 Notation for Objects Rectangular box with one or two compartments objectName: Classname field 1 = value 1 …… field n = value n The top compartment shows the name of the object and its class. The bottom compartment contains a list of the fields and their values. p1:Point x = 10 y = 20 p2:Point x = 20 y = 30

38. 38 Interfaces and Abstract Classes > Runnable +run(): void Shape {abstract}

39. Class Relationships Association Aggregation Composition Generalization Realization Dependency 39

40. 40 Association General binary relationships between classes Commonly represented as direct or indirect references between classes StudentCourse

41. 41 Association (Cont.) May have an optional label consisting of a name and a direction drawn as a solid arrowhead with no tail. The direction arrow indicates the direction of association with respect to the name. Student Course enroll

42. 42 Association (Cont.) An arrow may be attached to the end of path to indicate that navigation is supported in that direction If omitted? Student Course enroll

43. 43 Association (Cont.) May have an optional role name and an optional multiplicity specification. The multiplicity specifies an integer interval, e.g., –l..u closed (inclusive) range of integers –i singleton range –0..* entire nonnegative integer, i.e., 0, 1, 2, … Student Faculty adviseeadvisor 1 0..*

44. 44 Example StudentCourse has enrolled advisee advisor Faculty teach 1..* 6..* 0..* 1 1 1

45. 45 Aggregation Special form of association representing has-a or part-whole relationship. Distinguishes the whole (aggregate class) from its parts (component class). No relationship in the lifetime of the aggregate and the components (can exist separately). AggregateComponent

46. 46 Composition Stronger form of aggregation Implies exclusive ownership of the component class by the aggregate class The lifetime of the components is entirely included in the lifetime of the aggregate (a component can not exist without its aggregate). CompositionComponent

47. 47 Example Department member-of Faculty College chair-of Student 1 1 1 1 1 1 1..* 0..* 1..* University

48. 48 Dependency Relationship between the entities such that the proper operation of one entity depends on the presence of the other entity, and changes in one entity would affect the other entity. The common form of dependency is the use relation among classes. Class1Class2 >

49. 49 Complex Associations Associations may be: binary, ternary, or higher order. Binary associations involve two classes. This is the most common. Higher order associations are more complicated to draw, implement, and think about than binary associations. Ternary associations involve 3 objects: –It is an atomic unit –The division of a ternary association into binary associations may loose information –The associations are represented by a diamond

50. 50 Example Project Language Programmer Class diagram p1: Project C: Language Java: Language p2: Project Joe: Programmer Instance diagram

51. 51 Notation: Association Class Person Company 0..* 0..2 employer Employment period: DateRange Employment keeps information about the association that is not part of either object. Person could have two jobs. Employment is a 1-person/1- company relation. Association class

52. 52 Alternate Diagram Person Company 0..* 0..2 Employer Employment period: DateRange 0..2 1 1 0..*

53. 53 Recursive Associations Node 0..* node4 node2 node8 node1 node5 node6 node7 node3

54. 54 In Class: Draw the Class Diagram There are four classes: Program, Block, CompoundStatement, and SimpleStatement ::= program :. ::= * ::= | ::=

55. 55 Generalization and Specialization Customer Corporate Customer Private Customer Every attribute of Customer is also an attribute of its subclasses.

56. 56 In Class: Draw the Diagram A figure is either a group or a polygon. A group contains any number of figures.