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Bernd Bruegge & Allen Dutoit Object-Oriented Software Engineering: Conquering Complex and Changing Systems 1 Software Engineering September 5, 2001 Introduction to Software Engineering Joseph Conron Computer Science Department New York University jconron@cs.nyu.edu
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Bernd Bruegge & Allen Dutoit Object-Oriented Software Engineering: Conquering Complex and Changing Systems 2 What is Software Engineering Software systems are complex Impossible to understand by a single person Many projects are never finished: "vaporware" The problem is arbitrary complexity 1968 Definition: Software Engineering means the construction of quality software with a limited budget and a given deadline Our definition: Software Engineering means the construction of quality software with a limited budget and a given deadline in the context of constant change Emphasis is on both, on software and on engineering
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Bernd Bruegge & Allen Dutoit Object-Oriented Software Engineering: Conquering Complex and Changing Systems 3 Software Engineering Concepts: Definitions Project – set of activities to develop a software system Activity – a phase in which related tasks are carried out Task – effort that uses resources AND produces WorkProduct Resources – time, equipment, people (participants) WorkProduct – a model, system, or artifact
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Bernd Bruegge & Allen Dutoit Object-Oriented Software Engineering: Conquering Complex and Changing Systems 4 Software Engineering Concepts consumes Activity WorkProductResourcesTask Equipment Time ParticipantDocument Model System is produced by * * ** Project
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Bernd Bruegge & Allen Dutoit Object-Oriented Software Engineering: Conquering Complex and Changing Systems 5 Software Engineering Activities Requirements Elicitation Analysis System Design Object Design Implementation
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Bernd Bruegge & Allen Dutoit Object-Oriented Software Engineering: Conquering Complex and Changing Systems 6 Introduction to Modeling and UML What is modeling? What is UML? Use case diagrams Class diagrams Sequence diagrams Activity diagrams Summary
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Bernd Bruegge & Allen Dutoit Object-Oriented Software Engineering: Conquering Complex and Changing Systems 7 Systems, Models, and Views A model is an abstraction describing system or a subset of a system A view depicts selected aspects of a model A notation is a set of graphical or textual rules for representing views Views and models of a single system may overlap each other
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Bernd Bruegge & Allen Dutoit Object-Oriented Software Engineering: Conquering Complex and Changing Systems 8 Systems, Models, and Views Airplane Flightsimulator Scale Model Blueprints Electrical Wiring
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Bernd Bruegge & Allen Dutoit Object-Oriented Software Engineering: Conquering Complex and Changing Systems 9 Models, Views, and Systems (UML) View * * depicted by described by SystemModel flightSimulator:Model scaleModel:Model blueprints:View airplane:System fuelSystem:ViewelectricalWiring:View
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Bernd Bruegge & Allen Dutoit Object-Oriented Software Engineering: Conquering Complex and Changing Systems 10 Why model software? Software is already an abstraction: why model software? Software is getting larger, not smaller NT 5.0 ~ 40 million lines of code A single programmer cannot manage this amount of code in its entirety. Code is often not directly understandable by developers who did not participate in the development We need simpler representations for complex systems Modeling is a mean for dealing with complexity
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Bernd Bruegge & Allen Dutoit Object-Oriented Software Engineering: Conquering Complex and Changing Systems 11 Concepts and Phenomena Phenomenon: An object in the world of a domain as you perceive it, for example: The lecture you are attending My black watch Concept: Describes the properties of phenomena that are common, for example: Lectures on software engineering Black watches A concept is a 3-tuple: Its Name distinguishes it from other concepts. Its Purpose are the properties that determine if a phenomenon is a member of a concept. Its Members are the phenomena which are part of the concept.
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Bernd Bruegge & Allen Dutoit Object-Oriented Software Engineering: Conquering Complex and Changing Systems 12 Abstraction: Classification of phenomena into concepts Modeling: Development of abstractions to answer specific questions about a set of phenomena while ignoring irrelevant details. MembersName Clock Purpose A device that measures time. Concepts and Phenomena
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Bernd Bruegge & Allen Dutoit Object-Oriented Software Engineering: Conquering Complex and Changing Systems 13 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 relationship between “type” and “instance” is similar to that of “concept” and “phenomenon.” Abstract data type: Special type whose implementation is hidden from the rest of the system.
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Bernd Bruegge & Allen Dutoit Object-Oriented Software Engineering: Conquering Complex and Changing Systems 14 Class Class: An abstraction in the context of object-oriented languages Like an abstract data type, a class encapsulates both state (variables) and behavior (methods) Unlike abstract data types, classes can be defined in terms of other classes using inheritance Watch time date CalculatorWatch SetDate(d) EnterCalcMode() InputNumber(n) calculatorState
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Bernd Bruegge & Allen Dutoit Object-Oriented Software Engineering: Conquering Complex and Changing Systems 15 Object-Oriented Modeling UML Package
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Bernd Bruegge & Allen Dutoit Object-Oriented Software Engineering: Conquering Complex and Changing Systems 16 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
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Bernd Bruegge & Allen Dutoit Object-Oriented Software Engineering: Conquering Complex and Changing Systems 17 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, 1999. Supported by several CASE tools Rational ROSE Together/J ...
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Bernd Bruegge & Allen Dutoit Object-Oriented Software Engineering: Conquering Complex and Changing Systems 18 UML and This Course You can model 80% of most problems by using about 20% UML In this course, we teach you those 20%
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Bernd Bruegge & Allen Dutoit Object-Oriented Software Engineering: Conquering Complex and Changing Systems 19 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, and Associations. Sequence diagrams Describe the dynamic behavior between actors and the system and between objects of the system. Statechart diagrams Describe the dynamic behavior of an individual object as a finite state machine. Activity diagrams Model the dynamic behavior of a system, in particular the workflow, i.e. a flowchart.
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Bernd Bruegge & Allen Dutoit Object-Oriented Software Engineering: Conquering Complex and Changing Systems 20 UML First Pass: Use Case Diagrams WatchUserWatchRepairPerson ReadTime SetTime ChangeBattery Actor Use case Package SimpleWatch Use case diagrams represent the functionality of the system from user’s point of view
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Bernd Bruegge & Allen Dutoit Object-Oriented Software Engineering: Conquering Complex and Changing Systems 21 UML First Pass: Class Diagrams Battery load() 1 2 Time now() PushButton state push() release() 1 1 1 1 1 2 blinkIdx blinkSeconds() blinkMinutes() blinkHours() stopBlinking() referesh() LCDDisplay SimpleWatch Class Association Multiplicity Attributes Operations Class diagrams represent the structure of the system
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Bernd Bruegge & Allen Dutoit Object-Oriented Software Engineering: Conquering Complex and Changing Systems 22 UML First Pass: Sequence Diagram Object Message Activation Sequence diagrams represent the behavior as interactions blinkHours() blinkMinutes() incrementMinutes() refresh() commitNewTime() stopBlinking() pressButton1() pressButton2() pressButtons1And2() pressButton1() :WatchUser :Time:LCDDisplay:SimpleWatch
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Bernd Bruegge & Allen Dutoit Object-Oriented Software Engineering: Conquering Complex and Changing Systems 23 button1&2Pressed button1Pressed button2Pressed button1Pressed button1&2Pressed Increment Minutes Increment Hours Blink Hours Blink Seconds Blink Minutes Increment Seconds Stop Blinking UML First Pass: Statechart Diagrams State Initial state Final state Transition Event
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Bernd Bruegge & Allen Dutoit Object-Oriented Software Engineering: Conquering Complex and Changing Systems 24 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 (OCL) Introduced in lecture on Object Design
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