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The OO Solution

The OO Solution. The OO model closely resembles the problem domain Base your model on the objects in the problem domain Iteratively refine the high-level model until you have an implementation Attempt to avoid big conceptual jumps during the development process. Objects. State of Michigan.

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The OO Solution

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  1. The OO Solution • The OO model closely resembles the problem domain • Base your model on the objects in the problem domain • Iteratively refine the high-level model until you have an implementation • Attempt to avoid big conceptual jumps during the development process CSE870: UML Classes

  2. Objects State of Michigan Drivers License VISA J. Q. Public A-123456 03-12-63 J. Q. Public 123 4567 887766 998 CSE870: UML Classes

  3. Attributes and Operations Person objects Attributes name age height weight Operations move change-job abstracts to Card objects Card class Attributes height width id-number Operations issue change State of Michigan Drivers License VISA J. Q. Public A-123456 03-12-63 J. Q. Public 123 4567 887766 998 Person class

  4. Characteristics of Objects • Identity • Discrete and distinguishable entities • Classification • Abstract entities with the same structure (attributes) and behavior (operations) into classes • Polymorphism • The same operation may behave differently on different classes • Inheritance • Sharing of attributes and operations based on a hierarchical relationship CSE870: UML Classes

  5. The Class Diagrams CSE870: UML Classes

  6. Objects • Something that makes sense in the application context (application domain) • J.Q. Public • Joe’s Homework Assignment 1 • J. Q. Public’s drivers license • All objects have identity and are distinguishable • NOT objects • Person • Drivers license CSE870: UML Classes

  7. Classes • Describes a group of objects with similar properties (attributes), common behavior (operations), common relationships to other classes, and common semantics • Person • J. Q. Public • Joe Smith • D. Q. Public • Card • Credit card • Drivers license • Teller card CSE870: UML Classes

  8. Class Diagrams D. Q. Public: Person J. Q. Public: Person age= 32 age= 35 Class diagram Instance diagram Person age: integer Class with attributes Objects with values Objects have an identity Do not explicitly list object identifiers SSN OK! CSE870: UML Classes

  9. Examples CSE870: UML Classes

  10. Transformation that can be applied to or performed by an object May have arguments Operations and Methods CSE870: UML Classes

  11. Object Notation - Summary CSE870: UML Classes

  12. Associations • Conceptual connection between classes • A credit card is issued-by a bank • A person works-for a company Issued-by Credit Card Bank Class diagrams Works-for Person Company J.Q. Public: Person Michigan State Univ: Company Instance diagram Works-for Age=35 CSE870: UML Classes

  13. Associations are Bi-directional • There is no direction implied in an association (Rumbaugh - OMT) Country name City name Has-capital Person name Drivers-license lic.-number: integer Is-issued CSE870: UML Classes

  14. Associations Have Direction • Unified adds a direction indicator • Inconsistently used Country name City name Has-capital Person name Drivers-license lic.-number: integer Is-issued CSE870: UML Classes

  15. Multiplicity Person Credit-card Holds card-number: integer name: String • One object can be related to many objects through the same association One person holds one credit card One person can hold zero or more credit cards Holds Person Credit-card 0..* card-number: integer name: String CSE870: UML Classes

  16. Multiplicity (Cont.) Card456:Credit-Card Card123:Credit-Card Card789:Credit-Card card-number= 111 222 333 card-number= 123 456 789 card-number= 444 555 666 :JQPublic:Person :DQPublic:Person name= J. Q. Public age=35 name= D. Q. Public age=32 • One person can hold zero or more credit cards (0..*) • Each card has zero or one holder (0..1) Person Credit-card Holds 0..1 0..* card-number: integer name: String age: integer Holds Holds CSE870: UML Classes

  17. Higher order associations • Ternary association • Project, language, person • Seldom needed (and should be avoided) 1..* 1..* Language Project 1..* Person Compiler: Project C++ :Language Note: hexagons should be rectangles to represent instances J. Q. Public:Person Age=35 TicTacToe:Project LISP:Language CSE870: UML Classes

  18. Link Attributes • Associations can have properties the same way objects have properties How to represent salary and job title? Person Company name: String 0..* Works-for age: integer name: String SSN: integer address: String address: String Person Company name: String 0..* 8 Works-for age: integer name: String Use a link attribute! SSN: integer address: String address: String salary: integer job-title: String CSE870: UML Classes

  19. Folding Link Attributes Why not this? Salary and job title are properties of the job not the person Person name: String Company age: integer 0..* Works-for SSN: integer name: String address: String address: String salary: integer job-title: String Person Company name: String 0..* Works-for 0..* age: integer name: String In this case, a link attribute is the only solution SSN: integer address: String address: String salary: integer job-title: String CSE870: UML Classes

  20. Role Names Person Company name: String 0..* 0..* Works-for boss age: integer name: String employee employer 0..1 SSN: integer address: String address: String 0..* worker Manages salary: integer job-title: String • Attach names to the ends of an association to clarify its meaning CSE870: UML Classes

  21. Aggregation • A special association, the is-part-of association • A sentence is part of a paragraph (a paragraph consists of sentences) • A paragraph is part of a document (a document consists of paragraphs) 0..* 0..* Document Paragraph Sentence Aggregation symbol CSE870: UML Classes

  22. Aggregation (Cont.) • Often used in parts explosion Car 4 Wheel Body Gearbox Engine 1..* 1..* 0..* Door Hood Trunk Piston Valve Crankshaft CSE870: UML Classes

  23. The is-a association Cards have many properties in common Generalize the common properties to a separate class, the base-card Let all cards inherit from this class, all cards is-a base-card (plus possibly something more) Generalization and Inheritance Card height: integer width: integer thickness: integer id-number: integer issue() revoke() Drivers License ID Card Credit Card issued: date credit-limit: integer class: vehicle expires: date issued: date issued: date expires: date expire() validate() expire() CSE870: UML Classes

  24. Example Owns Pilot Works-for City Airline Based-In 0..* name name name 0..* license Located-In Offers 1..* Certified-On Pilots 0..* 0..* Airport 0..* Plane 0..* Departs Flight name 0..* model serial # date Used-For Arrives heat() hours flown flight # clean() 0..* cancel() heat() delay() refuel() clean() 30..* Seat 0..* Passenger location name Confirmed-for reserve()

  25. Aggregation Versus Association • Can you use the phrase is-part-of or is-made-of • Are operations automatically applied to the parts (for example, move) - aggregation • Not clear what it should be…… 0..* 0..* Company Division Department Works-for 0..* Person CSE870: UML Classes

  26. Do not confuse the is-a relation (inheritance) with the is-part-of relation (aggregation) Use inheritance for special cases of a general concept Use aggregation for parts explosion Aggregation Versus Inheritance 4 Wheel Body Car Gearbox Engine Minivan Compact Jeep Roll Bar CSE870: UML Classes

  27. Recursive Aggregates Program 0..* Block Compound Simple Statement Statement • A recursive aggregate contains (directly or indirectly) an instance of the same kind of aggregate CSE870: UML Classes

  28. Classes Name Attributes Operations Associations Roles Link attributes Aggregation Inheritance Object Modeling Summary CSE870: UML Classes

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