Chapter 2, Modeling with UML

Transcription

1 Object-Oriented Software Engineering Using UML, Patterns, and Java Chapter 2, Modeling with UML Overview: modeling with UML What is modeling? What is UML? Use case diagrams Class diagrams Next lecture Sequence diagrams Activity diagrams Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 2

2 What is modeling? Modeling consists of building an abstraction of reality. Abstractions are simplifications because: They ignore irrelevant details and They only represent the relevant details. What is relevant or irrelevant depends on the purpose of the model. Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 3 Example: street map Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 4

3 Why model software? Why model software? Software is getting increasingly more complex Windows XP > 40 mio lines of code A single programmer cannot manage this amount of code in its entirety. Code is not easily understandable by developers who did not write it We need simpler representations for complex systems Modeling is a mean for dealing with complexity Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 5 Systems, Models and Views A model is an abstraction describing a subset of a system A view depicts selected aspects of a model A notation is a set of graphical or textual rules for depicting views Views and models of a single system may overlap each other Examples: System: Aircraft Models: Flight simulator, scale model Views: All blueprints, electrical wiring, fuel system Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 6

4 Systems, Models and Views Aircraft System Blueprints Model 1 View 1 Flightsimulator Model 2 View 2 View 3 Scale Model Electrical Wiring Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 7 Models, Views and Systems (UML) System Model View Described by Depicted by Airplane: System Scale Model: Model Flight Simulator: Model Blueprints: View Fuel System: View Electrical Wiring: View Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 8

5 Concepts and Phenomena Phenomenon An object in the world of a domain as you perceive it Example: The lecture you are attending Example: My black watch Concept Describes the properties of phenomena that are common. Example: Lectures on software engineering Example: Black watches Concept is a 3-tuple: Name (To distinguish it from other concepts) Purpose (Properties that determine if a phenomenon is a member of a concept) Members (The set of phenomena which are part of the concept) Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 9 Concepts and phenomena Name Purpose Members Clock A device that measures time. Abstraction Classification of phenomena into concepts Modeling Development of abstractions to answer specific questions about a set of phenomena while ignoring irrelevant details. Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 10

6 Concepts in software: Type and Instance Type: An abstraction in the context of programming languages Name: int, Purpose: integral number, Members: 0, -1, 1, 2, -2,... Instance: Member of a specific type The type of a variable represents all possible instances the variable can take The following relationships are similar: type < > instance concept < > phenomenon Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 11 Abstract Data Types & Classes Abstract data type (ex, stack, queue) Special type whose implementation is hidden from the rest of the system. Class: (ex, Template) An abstraction in the context of objectoriented languages Like an abstract data type, a class encapsulates both state (variables) and behavior (methods) Class Vector Unlike abstract data types, classes can be defined in terms of other classes using inheritance time date Watch SetDate(d) CalculatorWatch calculatorstate EnterCalcMode() InputNumber(n) Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 12

7 Application and Solution Domain Application Domain (Requirements Analysis): The environment in which the system is operating Solution Domain (System Design, Object Design): The available technologies to build the system Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 13 Object-oriented modeling Application Domain Application Domain Model TrafficControl UML Package Solution Domain System Model SummaryDisplay MapDisplay Aircraft TrafficController FlightPlanDatabase FlightPlan Airport TrafficControl Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 14

8 What is UML? UML (Unified Modeling Language) An emerging standard for modeling object-oriented software. Resulted from the convergence of notations from three leading object-oriented methods: OMT (James Rumbaugh) OOSE (Ivar Jacobson) Booch (Grady Booch) Reference: The Unified Modeling Language User Guide, Addison Wesley, Supported by several CASE tools Rational ROSE TogetherJ HiMEM ver 1.0 Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 15 UML: First Pass You can model 80% of most problems by using about 20 % UML We teach you those 20% Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 16

9 UML First Pass Use case Diagrams Describe the functional behavior of the system as seen by the user. Class diagrams Describe the static structure of the system: Objects, Attributes, Associations Sequence diagrams Describe the dynamic behavior between actors and the system and between objects of the system Statechart diagrams (=State machine, State Transition Diagram) Describe the dynamic behavior of an individual object (essentially a finite state automaton) Activity Diagrams Model the dynamic behavior of a system, in particular the workflow (essentially a flowchart) Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 17 UML first pass: Use case diagrams Package Watch Use case Actor ReadTime WatchUser SetTime WatchRepairPerson ChangeBattery Use case diagrams represent the functionality of the system from user s point of view Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 18

10 UML first pass: Class diagrams Class diagrams represent the structure of the system Association Class Multiplicity Watch PushButton state push() release() 1 LCDDisplay blinkidx blinkseconds() blinkminutes() blinkhours() stopblinking() referesh() 2 Battery load 1 Time now Attribute Operations Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 19 UML first pass: Sequence diagram Actor Object :WatchUser :Watch :LCDDisplay :Time Message pressbutton1() blinkhours() pressbutton1() blinkminutes() pressbutton2() pressbuttons1and2() stopblinking() incrementminutes() refresh() commitnewtime() Activation Lifeline Sequence diagrams represent the behavior as interactions Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 20

11 UML first pass: Statechart diagrams for objects with interesting dynamic behavior Event Initial state State [button1&2pressed] BlinkHours [button2pressed] IncrementHrs Transition [button1pressed] [button1&2pressed] BlinkMinutes [button2pressed] IncrementMin. [button1pressed] [button1&2pressed] [button2pressed] BlinkSeconds IncrementSec. StopBlinking Final state Represent behavior as states and transitions Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 21 Other UML Notations UML provide other notations that we will be introduced in subsequent lectures, as needed. Implementation diagrams Component diagrams Deployment diagrams Introduced in lecture on System Design Object constraint language Introduced in lecture on Object Design Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 22

12 UML Core Conventions Rectangles are classes or instances Ovals are functions or use cases Instances are denoted with an underlined names mywatch:simplewatch Joe:Firefighter Types are denoted with non underlined names SimpleWatch Firefighter Diagrams are graphs Nodes are entities Arcs are relationships between entities Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 23 Use Case Diagrams Used during requirements elicitation to represent external behavior Passenger PurchaseTicket Actors represent roles, that is, a type of user of the system Use cases represent a sequence of interaction for a type of functionality The use case model is the set of all use cases. It is a complete description of the functionality of the system and its environment Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 24

13 Actors Passenger An actor models an external entity which communicates with the system: User External system Physical environment An actor has a unique name and an optional description. Examples: Passenger: A person in the train GPS satellite: Provides the system with GPS coordinates Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 25 Use Case A use case represents a set of functionality provided by the system as an event flow. PurchaseTicket A use case consists of: Unique name Participating actors Entry conditions Flow of events Exit conditions Special requirements Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 26

14 Use Case Diagram: Example Name: Purchase ticket Participating actor: Passenger Entry condition: Passenger standing in front of ticket distributor. Passenger has sufficient money to purchase ticket. Event flow: 1. Passenger selects the number of zones to be traveled. 2. Distributor displays the amount due. 3. Passenger inserts money, of at least the amount due. 4. Distributor returns change. 5. Distributor issues ticket. Exit condition: Passenger has ticket. Anything missing? Exceptional cases! Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 27 The <<extends>> Relationship Passenger PurchaseTicket <<extends>> <<extends>> <<extends>> relationships represent exceptional or seldom invoked cases. The exceptional event flows are factored out of the main event flow for clarity. Use cases representing exceptional flows can extend more than one use case. The direction of a <<extends>> relationship is to the extended use case <<extends>> OutOfOrder <<extends>> TimeOut Cancel NoChange Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 28

15 The <<includes>> Relationship Passenger PurchaseMultiCard PurchaseSingleTicket <<includes>> <<includes>> <<includes>> relationship represents behavior that is factored out of the use case. <<includes>> behavior is factored out for reuse, not because it is an exception. The direction of a <<includes>> relationship is to the using use case (unlike <<extends>> relationships). <<extends>> CollectMoney <<extends>> NoChange Cancel Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 29 Use Case Diagrams: Summary Use case diagrams represent external behavior Use case diagrams are useful as an index into the use cases Use case descriptions provide contents of model, not the use case diagrams. All use cases need to be described for the model to be useful. Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 30

16 Class Diagrams TarifSchedule Enumeration getzones() Price getprice(zone) Trip zone:zone Price: Price Class diagrams represent the structure of the system. Used during requirements analysis to model problem domain concepts during system design to model subsystems and interfaces during object design to model classes. Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 31 Classes TarifSchedule zone2price getzones() getprice() Name Attributes Operations TarifSchedule Table zone2price Enumeration getzones() Price getprice(zone) Signature TarifSchedule A class represent a concept (or we can say Template ) A class encapsulates state (attributes) and behavior (operations or methods). Each attribute has a type. Each operation has a signature. (that is, types of its parameters and of the return value) The class name is the only mandatory information. Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 32

17 Instances tarif_1974:tarifschedule zone2price = { { 1,.20}, { 2,.40}, { 3,.60}} An instance represents a phenomenon. The name of an instance is underlined and can contain the class of the instance. The attributes are represented with their values. Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 33 Actor vs Instances What is the difference between an actor, a class and an instance? Actor: An entity outside the system to be modeled, interacting with the system ( Passenger ) Class: An abstraction modeling an entity in the problem domain, must be modeled inside the system ( User ) Object: A specific instance of a class ( Joe, the passenger who is purchasing a ticket from the ticket distributor ). Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 34

18 Associations TarifSchedule Enumeration getzones() Price getprice(zone) TripLeg Price Zone Associations denote relationships between classes. The multiplicity of an association end denotes how many objects the source object can legitimately reference. Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 35 public class Gugudan { { { public static void main(string args[]) for(int i=2; i<10; i++) System.out.println("===== " + i + " 단 " + " =============="); Gugu gugu = new Gugu(); gugu.operation(i); } } } class Gugu { private int sum = 0; public void Operation(int i) { for(int j=2; j<10; j++) { sum = i j; if(j == 5 j == 9) { } { } } else System.out.print("\n"); System.out.println(i + " " + j + " = " + sum); System.out.print(i + " " + j + " = " + sum + "\t"); } } Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 36

19 1-to-1 and 1-to-many Associations Country name:string Has-capital City name:string One-to-one association Polygon draw() Point x: Integer y: Integer One-to-many association Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 37 Many-to-Many Associations StockExchange Lists Company tickersymbol StockExchange tickersymbol Lists 1 SX_ID Company Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 38

20 From Problem Statement To Object Model Problem Statement: A stock exchange lists many companies. Each company is uniquely identified by a ticker symbol Class Diagram: StockExchange Lists Company tickersymbol Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 39 From Problem Statement to Code Problem Statement : A stock exchange lists many companies. Each company is identified by a ticker Symbol Class Diagram: StockExchange Lists Company tickersymbol Java Code public class StockExchange { private Vector m_company = new Vector(); }; public class Company { public int m_tickersymbol; private Vector m_stockexchange = new Vector(); }; Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 40

21 Aggregation ( whole_of, HAS_A relationship) An aggregation is a special case of association denoting a consists of hierarchy. The aggregate is the parent class, the components are the children class. Exhaust system Exhaust system Muffler Tailpipe diameter diameter Muffler Tailpipe diameter diameter A solid diamond denotes composition, a strong form of aggregation where components cannot exist without the aggregate. (Bill of Material) TicketMachine 3 ZoneButton Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 41 Qualifiers Without qualification Directory 1 File filename With qualification Directory filename File Qualifiers can be used to reduce the multiplicity of an association. Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 42

22 Inheritance (Generalization; IS-A relationship) Button Parent class CancelButton Children classes ZoneButton The children classes inherit the attributes and operations of the parent class. Inheritance simplifies the model by eliminating redundancy. Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 43 Object Modeling in Practice: Class Identification Foo Betrag CustomerId Deposit() Withdraw() GetBalance() Class Identification: Name of Class, Attributes and Methods Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 44

23 Object Modeling in Practice: Encourage Brainstorming Dada Betrag CustomerId Deposit() Withdraw() GetBalance() Foo Betrag CustomerId Deposit() Withdraw() GetBalance() Account Betrag CustomerId Naming is important! Is Foo the right name? Deposit() Withdraw() GetBalance() Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 45 Object Modeling in Practice ctd Account Bank Name Betrag CustomerId AccountId Deposit() Withdraw() GetBalance() Customer Name CustomerId 1) Find New Objects 2) Iterate on Names, Attributes and Methods Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 46

24 Object Modeling in Practice: A Banking System Account Bank Name Betrag CustomerId AccountId AccountI d Deposit() Withdraw() GetBalance() Has Customer Name CustomerId 1) Find New Objects 2) Iterate on Names, Attributes and Methods 3) Find Associations between Objects 4) Label the assocations 5) Determine the multiplicity of the assocations Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 47 Practice Object Modeling: Iterate, Categorize! Bank Name Account Amount CustomerId AccountId AccountI d Deposit() Withdraw() GetBalance() Has Customer Name CustomerId() Savings Account Checking Account Mortgage Account Withdraw() Withdraw() Withdraw() Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 48

25 Packages A package is a UML mechanism for organizing elements into groups (usually not an application domain concept) Packages are the basic grouping construct with which you may organize UML models to increase their readability. DispatcherInterface Notification IncidentManagement A complex system can be decomposed into subsystems, where each subsystem is modeled as a package Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 49 UML sequence diagrams TicketMachine Passenger selectzone() insertcoins() pickupchange() pickupticket() Used during requirements analysis To refine use case descriptions to find additional objects ( participating objects ) Used during system design to refine subsystem interfaces Classes are represented by columns Messages are represented by arrows Activations are represented by narrow rectangles Lifelines are represented by dashed lines Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 50

26 Nested messages Passenger selectzone() ZoneButton TarifSchedule Display lookupprice(selection) price Dataflow displayprice(price) to be continued... The source of an arrow indicates the activation which sent the message An activation is as long as all nested activations Horizontal dashed arrows indicate data flow Vertical dashed lines indicate lifelines Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 51 Iteration & condition continued from previous slide... ChangeProcessor CoinIdentifier Display CoinDrop Passenger insertchange(coin) lookupcoin(coin) Iteration price displayprice(owedamount) Condition [owedamount<0] returnchange(-owedamount) to be continued... Iteration is denoted by a preceding the message name Condition is denoted by boolean expression in [ ] before the message name Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 52

27 Creation and destruction continued from previous slide... Passenger ChangeProcessor createticket(selection) Creation print() Ticket free() Destruction Creation is denoted by a message arrow pointing to the object. Destruction is denoted by an X mark at the end of the destruction activation. In garbage collection environments, destruction can be used to denote the end of the useful life of an object. Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 53 Sequence Diagram Summary UML sequence diagram represent behavior in terms of interactions. Useful to find missing objects. Time consuming to build but worth the investment. Complement the class diagrams (which represent structure). Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 54

28 State Chart Diagrams Event Initial state State [button1&2pressed] Transition BlinkHours [button1pressed] [button2pressed] IncrementHrs [button1&2pressed] BlinkMinutes [button2pressed] IncrementMin. [button1pressed] [button1&2pressed] [button2pressed] BlinkSeconds IncrementSec. StopBlinking Final state Represent behavior as states and transitions Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 55 Activity Diagrams An activity diagram shows flow control within a system Handle Incident Document Incident Archive Incident An activity diagram is a special case of a state chart diagram in which states are activities ( functions ) Two types of states: Action state: Cannot be decomposed any further Happens instantaneously with respect to the level of abstraction used in the model Activity state: Can be decomposed further The activity is modeled by another activity diagram Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 56

29 Statechart Diagram vs. Activity Diagram Statechart Diagram for Incident (similar to Mealy Automaton) (State: Attribute or Collection of Attributes of object of type Incident) Event causes State transition Active Inactive Closed Archived Incident- Incident- Incident- Handled Documented Archived Activity Diagram for Incident (similar to Moore (State: Operation or Collection of Operations) Handle Incident Document Incident Archive Incident Completion of activity causes state transition Triggerless Transition Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 57 Activity Diagram: Modeling Decisions Open Incident [lowpriority] [fire & highpriority] Allocate Resources [not fire & highpriority] Notify Fire Chief Notify Police Chief Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 58

30 Activity Diagrams: Modeling Concurrency Synchronization of multiple activities Splitting the flow of control into multiple threads Splitting Allocate Resources Synchronization Open Incident Coordinate Resources Archive Incident Document Incident Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 59 Activity Diagrams: Swimlanes Actions may be grouped into swimlanes to denote the object or subsystem that implements the actions. Allocate Resources Dispatcher Open Incident Coordinate Resources Archive Incident Document Incident FieldOfficer Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 60

31 What should be done first? Coding or Modeling? It all depends. Forward Engineering: Creation of code from a model Greenfield projects Reverse Engineering: Creation of a model from code Interface or reengineering projects (legacy) Roundtrip Engineering: Move constantly between forward and reverse engineering Useful when requirements, technology and schedule are changing frequently Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 61 UML Summary UML provides a wide variety of notations for representing many aspects of software development Powerful, but complex language Can be misused to generate unreadable models Can be misunderstood when using too many exotic features For now we concentrate on a few notations: Functional model: Use case diagram Object model: class diagram Dynamic model: sequence diagrams, statechart and activity diagrams Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 62

32 Additional Slides Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 63 Models for Plato s and Aristotle s Views of Reality Plato Material reality is a second-class subordinate type of reality. The first-class type is a form Forms lie behind every thing or in the world. Forms can be abstract nouns like beauty or mammal or concrete nouns like tree or horse. There is an important difference between the world of forms and particulars. Forms are nonmaterial, particulars are material. Forms are permanent and changeless. Particulars are changing. Forms can be acquired intellectually through a dialectic process that moves toward the highest understanding of reality through the interaction of questions and answers. Aristotle Aristotle accepted the reality of Forms as nonmaterial entities. However, he could not accept Plato s idea, that these Forms were not real. Instead of two separate worlds, one for Forms and one for Particulars, Aristotle had only one world, a world of particular things. Particular things according to Aristotle have a certain permance about them, even while they are subject to change: A tree changes colors without ceasing to be a tree. A horse grows in size without ceasing to be a horse. What is the root of this permancence? It is the thing s internal form, which minds detect, when they penetrate beyond the thing s changing attributes. So for Aristotle, reality is thus made up of particular things that are each composed of form antdn matter.. Using UML, we can illustrate Platon s and Aristotle s viewpoints very easily and see their differences as well Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 64

33 Model for Plato s View of Reality Plato Material reality is a secondclass subordinate type of reality. The first-class type is a form Forms lie behind every thing or in the world. Forms can be abstract nouns like beauty or mammal or concrete nouns like tree or horse. There is an important difference between the world of forms and particulars. Forms are nonmaterial, particulars are material. Forms are permanent and changeless. Particulars are changing. Forms can be acquired intellectually through a dialectic process that moves toward the highest understanding of reality th h th i t ti f Particular Reality Thing Form Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 65 Model Aristotle s Views of Reality Aristotle Aristotle accepted the reality of Forms as nonmaterial entities. However, he could not accept Plato s idea, that these Forms were not real. Instead of two separate worlds, one for Forms and one for Particulars, Aristotle had only one world, a world of particular things. Particular things according to Aristotle have a certain permance about them, even while they are subject to change: A tree changes colors without ceasing to be a tree. A horse grows in size without ceasing to be a horse. What is the root of this permancence? It is the thing s internal form, which minds detect, when they penetrate beyond the thing s changing attributes. So for Aristotle, reality is thus made up of particular things that are each composed of form antdn matter Form Reality Substance Matter Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 66

34 Comparison of Plato s and Aristotle s Views Plato Aristotle Reality Reality Thing Substance Form Matter Particular Form Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 67