1 welcome

2 Object Oriented Software Systems Engineering Meetings: Every second Saturday, 9:00-15:30pm Instructor: Panayiotis Alefragis

3 Course Topics Software development methodology Object-oriented What is most likely to happen in real world software development Requirements analysis Domain analysis and modeling Design Iterative development with Java Testing

4 Goals Apply requirements and domain analysis Apply design with objects Apply patterns – principles and idioms to use Object-oriented design Assigning responsibility to software components Apply UML Learn an Object Oriented Language (Java) Apply iterative development Apply testing strategies

5 Lecture Outline Intro Topics Goals Prerequisites Overview Example Syllabus Software Engineering Principles Iterative Development and the Unified Process (UP)

6 Overview Example, Step 1: Requirements, Use-Case Model Not an object-oriented step. Use case: Play Dice Game Main success scenario: Player picks up the two dice and rolls them. If face value is 7 then they win … Else …

7 Example, Step 2: Domain Model Player name Die face value Dice Game Rolls Includes Plays

8 Example, Step 3: Design: Interaction Diagram Dynamic object design :Dice GameDie1 :DieDie2 :Die play() roll() fv1:= getFaceValue() roll() fv2:= getFaceValue()

9 Example, Step 3: Design: Class Diagram Static design Dice Game play() Die faceValue : int getFaceValue() : int roll() 12

10 Example, step 4: Object-oriented Program Dice Game die1 : Die die2 : Die play() class DiceGame { private Die die1 = new Die(); private Die die2 = new Die(); public void play() { die1.roll(); int fv1 = die1.getFaceValue(); … } } :Dice GameDie1 :DieDie2 :Die roll() fv1:=getFaceValue() fv2:=getFaceValue() play()

11 Artifact Influence Use-Case Model Domain Model Design Model (Static and Dynamic Diagrams) OO Code (Java, C++, C#)

12 Syllabus What are we going to do in this class? UML Structural Diagrams UML Behavioral Diagrams Complete Design Example Intro Require ments and Use Cases 1 week 2 weeks 1 week Project Introduction to Java Company issues Testing Deployment Advanced Java GUI, Threads, Exceptions, Network, security, JDBC Selection & Integration OOAD with Developme nt Tools Patterns Frameworks Architectures Enterprise Programming

13 Syllabus Project Presentations Due: Documents, Design model & Final Code Teams of 2-4 people Assignment: Write your resume To be used for team selections. them to me until next Friday Exams

14 Syllabus Visual Paradigm Suite(CASE tool) JBuilder (IDE tool) Books UML Distilled 3rd Edition Applying UML and Patterns Object Oriented Design with Java and UML Java How to Program What are we going to use in this class?

15 Lecture Outline Intro Topics Goals Prerequisites Overview Example Syllabus Software Engineering Principles Iterative Development and the Unified Process

The Nature of Software... Software is intangible Hard to understand development effort Software is easy to reproduce Cost is in its development in other engineering products, manufacturing is the costly stage The industry is labor-intensive Hard to automate

17 The Nature of Software... Untrained people can hack something together Quality problems are hard to notice Software is easy to modify People make changes without fully understanding it Software does not ‘ wear out ’ It deteriorates by having its design changed: erroneously, or in ways that were not anticipated, thus making it complex

18 The Nature of Software Conclusions Much software has poor design and is getting worse Demand for software is high and rising We are in a perpetual ‘ software crisis ’ We have to learn to ‘ engineer ’ software

19 Types of Software... Custom For a specific customer Generic Sold on open market Often called COTS (Commercial Off The Shelf) Shrink-wrapped Embedded Built into hardware Hard to change

20 Types of Software Differences among custom, generic and embedded software

21 Types of Software Real time software E.g. control and monitoring systems Must react immediately Safety often a concern Data processing software Used to run businesses Accuracy and security of data are key Some software has both aspects

What is Software Engineering?... The process of solving customers ’ problems by the systematic development and evolution of large, high-quality software systems within cost, time and other constraints Solving customers ’ problems This is the goal of software engineering Sometimes the solution is to buy, not build Adding unnecessary features does not help solve the problem Software engineers must communicate effectively to identify and understand the problem

23 What is Software Engineering? … Systematic development and evolution An engineering process involves applying well understood techniques in a organized and disciplined way Many well-accepted practices have been formally standardized e.g. by the IEEE or ISO Most development work is evolution Large, high quality software systems Software engineering techniques are needed because large systems cannot be completely understood by one person Teamwork and co-ordination are required Key challenge: Dividing up the work and ensuring that the parts of the system work properly together The end-product that is produced must be of sufficient quality

24 What is Software Engineering? Cost, time and other constraints Finite resources The benefit must outweigh the cost Others are competing to do the job cheaper and faster Inaccurate estimates of cost and time have caused many project failures

Software Engineering and the Engineering Profession The term Software Engineering was coined in 1968 People began to realize that the principles of engineering should be applied to software development Engineering is a licensed profession In order to protect the public Engineers design artifacts following well accepted practices which involve the application of science, mathematics and economics Ethical practice is also a key tenet of the profession

Stakeholders in Software Engineering 1. Users Those who use the software 2. Customers Those who pay for the software 3. Software developers 4. Development Managers All four roles can be fulfilled by the same person

Software Quality... Usability Users can learn it and fast and get their job done easily Efficiency It doesn ’ t waste resources such as CPU time and memory Reliability It does what it is required to do without failing Maintainability It can be easily changed Reusability Its parts can be used in other projects, so reprogramming is not needed

28 Software Quality... QUALITY SOFTWARE Developer: easy to design; easy to maintain; easy to reuse its parts User: easy to learn; efficient to use; helps get work done Customer: solves problems at an acceptable cost in terms of money paid and resources used Development manager: sells more and pleases customers while costing less to develop and maintain

29 Software Quality The different qualities can conflict Increasing efficiency can reduce maintainability or reusability Increasing usability can reduce efficiency Setting objectives for quality is a key engineering activity You then design to meet the objectives Avoids ‘ over-engineering ’ which wastes money Optimizing is also sometimes necessary E.g. obtain the highest possible reliability using a fixed budget

30 Internal Quality Criteria These: Characterize aspects of the design of the software Have an effect on the external quality attributes E.g. The amount of commenting of the code The complexity of the code

31 Short Term Vs. Long Term Quality Short term: Does the software meet the customer ’ s immediate needs? Is it sufficiently efficient for the volume of data we have today? Long term: Maintainability Customer ’ s future needs

Software Engineering Projects Most projects are evolutionary or maintenance projects, involving work on legacy systems Corrective projects: fixing defects Adaptive projects: changing the system in response to changes in Operating system Database Rules and regulations Enhancement projects: adding new features for users Reengineering or perfective projects: changing the system internally so it is more maintainable

33 Software Engineering Projects ‘ Green field ’ projects New development The minority of projects

34 Software Engineering Projects Projects that involve building on a framework or a set of existing components. The framework is an application that is missing some important details. E.g. Specific rules of this organization. Such projects: Involve plugging together components that are: Already developed. Provide significant functionality. Benefit from reusing reliable software. Provide much of the same freedom to innovate found in green field development.

Activities Common to Software Projects... Requirements and specification Includes Domain analysis Defining the problem Requirements gathering Obtaining input from as many sources as possible Requirements analysis Organizing the information Requirements specification Writing detailed instructions about how the software should behave

36 Activities Common to Software Projects... Design Deciding how the requirements should be implemented, using the available technology Includes: Systems engineering: Deciding what should be in hardware and what in software Software architecture: Dividing the system into subsystems and deciding how the subsystems will interact Detailed design of the internals of a subsystem User interface design Design of databases

37 Activities Common to Software Projects Modeling Creating representations of the domain or the software Use case modeling Structural modeling Dynamic and behavioural modeling Programming Quality assurance Reviews and inspections Testing Deployment Managing the process

Difficulties and Risks in Software Engineering Complexity and large numbers of details Uncertainty about technology Uncertainty about requirements Uncertainty about software engineering skills Constant change Deterioration of software design Political risks

39 Lecture Outline Intro Topics Goals Prerequisites Overview Example Syllabus Software Engineering Principles Iterative Development and the Unified Process

40 Iterative Development and the Unified Process (UP) Iterative Development A software development methodology Repeat software development disciplines, such as analysis, design, etc. State-of-the-art approach The Unified Process An instance of iterative development Well-known, you are likely to be exposed to it Other: XP, Agile development, etc.

41 The Sequential “ Waterfall ” Lifecycle Most requirements, Defined and Stabilized Design Implementation Integration and Testing Long lifecycle 6 months

42 Iterative Lifecycle: Short Iterations Requirements Design Implementation & Test & Integration & More Design Final Integration & System Test Requirements Design Implementation & Test & Integration & More Design Final Integration & System Test feedback Short 2-6 weeks Iterations are fixed in length, timeboxed System grows incrementally

43 Iterative Development Lifecycle 123 … Use case: process sale New use case: process rental

44 Disciplines Across Iterations UP Disciplines Business Modeling Requirements Design Implementation …

45 Key Ideas in UP High risks early on, drive down Managerial Technical Integration of subsystems, as early as possible Test and validate early Related to risk Feedback

46 Key Ideas in UP Research shows that UP works better than the “ waterfall ” approach. Why? Change

47 Disciplines Across Iterations UP Disciplines Business Modeling Requirements Design Implementation … InceptionElaborationConstruction Transition

48 Our Course Requirements & use case modeling Other requirements inceptionelaboration … OO Analysis OO Design Translating Design to Code

49 True or false? Inception = Requirements Elaboration = Design Construction = Implementation But …

50 Object Orientation Analyzing requirements? Design? Construction? Maintenance? Usability?