1. © Lethbridge/Laganière 2005 Chapter 1: Software and Software Engineering1 Warm Up Question: What do you think are the most important attributes of a piece of well written software: Answer: - that it works and gives the correct results  reliability - WHAT ELSE (can you think of 3 more?): - “In the force if Yoda's so strong, construct a sentence with words in the proper order then why can't he?”

2. Object-Oriented Software Engineering Practical Software Development using UML and Java Chapter 1: Software and Software Engineering Timing: 40 minutes

3. © Lethbridge/Laganière 2005 Chapter 1: Software and Software Engineering3 What are some differences between developing and manufacturing the latest Mustang automobile from Ford vs. developing and manufacturing the latest computer game for the Wii from Nintendo?

4. © Lethbridge/Laganière 2005 Chapter 1: Software and Software Engineering4 1.1 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

5. © Lethbridge/Laganière 2005 Chapter 1: Software and Software Engineering5 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

6. © Lethbridge/Laganière 2005 Chapter 1: Software and Software Engineering6 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

7. © Lethbridge/Laganière 2005 Chapter 1: Software and Software Engineering7 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

8. © Lethbridge/Laganière 2005 UWO - Computer Science8 Review Why Laura should stop saying CS2212 is wishy washy!

9. © Lethbridge/Laganière 2005 Chapter 1: Software and Software Engineering9 Hint: Consider building (or perhaps engineering) a bridge: vs. What do you think the term: “Software Engineering” means or implies?

10. © Lethbridge/Laganière 2005 Chapter 1: Software and Software Engineering10 1.2 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

11. © Lethbridge/Laganière 2005 Chapter 1: Software and Software Engineering11 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

12. © Lethbridge/Laganière 2005 Chapter 1: Software and Software Engineering12 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 Example of an interesting software problemExample of an interesting software problem There are hundreds of thousands of problems like this!

13. © Lethbridge/Laganière 2005 Chapter 1: Software and Software Engineering13 1.3 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 Take personal responsibility for the work created

14. © Lethbridge/Laganière 2005 Chapter 1: Software and Software Engineering14 1.4 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

15. © Lethbridge/Laganière 2005 Chapter 1: Software and Software Engineering15 Think of one or two of your favourite activities to do on the computer, what about the software written for those activities made the activity more enjoyable? Think about a piece of software you purchased where you installed it but hardly ever used it? Why didn’t you use it? Did it have to do with the software, if so, specifically what did you hate?

16. © Lethbridge/Laganière 2005 Chapter 1: Software and Software Engineering16 1.5 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

17. © Lethbridge/Laganière 2005 Chapter 1: Software and Software Engineering17 Wikipedia, in defining software engineering mentions the ilities, what are ilities? http://en.wikipedia.org/wiki/Ilities

18. © Lethbridge/Laganière 2005 Chapter 1: Software and Software Engineering18 Of the 5 most important attributes of software quality: Usability, Maintainability, Reliability, Reusability and Efficiency, which ones do YOU think would be most important to each of the four stakeholders? StakeholderMost ImportantLeast Important User Customer Developer Development manager

19. © Lethbridge/Laganière 2005 Chapter 1: Software and Software Engineering19 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

20. © Lethbridge/Laganière 2005 Chapter 1: Software and Software Engineering20 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 Question: Can you think how of two of the five qualities could conflict, for example how could Efficiency and Maintainability conflict?

21. © Lethbridge/Laganière 2005 UWO - Computer Science21 Review For each of the following systems, which attributes of quality would be most and least important? Justify your answer. a web based banking system, enabling the user to do all aspects of banking on line an air traffic control system a program that will enable users to view digital images or movies stored in all known formats a system to manage the work schedule of nurses that respects all the constraints and regulations in force at a particular hospital an application that allows you to purchase any thing seen while watching TV

22. © Lethbridge/Laganière 2005 Chapter 1: Software and Software Engineering22 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

23. © Lethbridge/Laganière 2005 Chapter 1: Software and Software Engineering23 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

24. © Lethbridge/Laganière 2005 Chapter 1: Software and Software Engineering24 1.6 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

25. © Lethbridge/Laganière 2005 Chapter 1: Software and Software Engineering25 Software Engineering Projects ‘Green field’ projects New development The minority of projects What is the one area where you might be working on a new project, hint: we have a minor in it!

26. © Lethbridge/Laganière 2005 Chapter 1: Software and Software Engineering26 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.

27. © Lethbridge/Laganière 2005 Chapter 1: Software and Software Engineering27 Are you planning to do a degree with a minor in Software Engineering? Courses you could take in third and fourth year are: 3307  OO Design and Analysis 3377  Software Project Management 4470  Software Maintenance 4471  Software Design 4472  Testing 4473  Requirements Analysis 4474  Human Computer Interaction

28. © Lethbridge/Laganière 2005 Chapter 1: Software and Software Engineering28 1.7 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

29. © Lethbridge/Laganière 2005 Chapter 1: Software and Software Engineering29 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

30. © Lethbridge/Laganière 2005 Chapter 1: Software and Software Engineering30 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

31. © Lethbridge/Laganière 2005 Chapter 1: Software and Software Engineering31 1.8 The Nine Themes of the Book 1. Understanding the customer and the user 2. Basing development on solid principles and reusable technology 3. Object orientation 4. Visual modeling using UML 5. Evaluation of alternatives 6. Incorporating quantitative and logical thinking 7. Iterative development 8. Communicating effectively using documentation 9. Risk management in all SE activities

32. © Lethbridge/Laganière 2005 Chapter 1: Software and Software Engineering32 1.9 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 At UWO  use of clickers in the classroom is a perfect example of a lot of the issues above!

33. © Lethbridge/Laganière 2005 Chapter 1: Software and Software Engineering33 Let’s Review 1. According to our textbook what the 5 key features of high quality software? 2. Name one of the key terms in the definition our book gives for software engineering. 3. Last question: decide for each of the following two scenarios, which of the 5 features of high quality software you would focus on: a. A game for 4 years to teach them to read b. A tool to help your parent’s auto-body shop keep track of payroll.