W1 - The Scope of Software Engineering (1).pdf

CS-6209 Software Engineering 1 1 Week 1: The Scope of Software Engineering Module 001: The Scope of Software Engineering Course Learning Outc...

CS-6209 Software Engineering 1 1 Week 1: The Scope of Software Engineering Module 001: The Scope of Software Engineering Course Learning Outcomes: 1. Understand what software engineering is and why it is important; 2. Understand that the development of different types of software Systems may require different software engineering techniques; 3. Understand some ethical and professional issues that are important for software engineers; 4. Understand the scope of Software Engineering Introduction The term software engineering is composed of two words, software and engineering. Software is more than just a program code. A program is an executable code, which serves some computational purpose. Software is considered to be a collection of executable programming code, associated libraries and documentations. Software, when made for a specific requirement is called software product. Engineering on the other hand, is all about developing products, using well-defined, scientific principles and methods. So, we can define software engineering as an engineering branch associated with the development of software product using well-defined scientific principles, methods and procedures. The outcome of software engineering is an efficient and reliable software product. IEEE defines software engineering as: The application of a systematic, disciplined, quantifiable approach to the development, operation and maintenance of software. We can alternatively view it as a systematic collection of past experience. The experience is arranged in the form of methodologies and guidelines. A small program can be written without using software engineering principles. But if one wants to develop a large software product, then software engineering principles are absolutely necessary to achieve a good quality software cost effectively. Without using software engineering principles it would be difficult to develop large programs. In industry it is usually needed to develop large programs to accommodate multiple functions. A problem with developing such large commercial programs is that the complexity and difficulty levels of the programs increase exponentially with their sizes. Software engineering helps to reduce this programming complexity. Software engineering principles use two important techniques to reduce problem complexity: abstraction and decomposition. The principle of abstraction implies that a problem can be simplified by omitting irrelevant details. In other words, the main purpose of abstraction is to consider only those aspects of the problem that are relevant for certain purpose and suppress other aspects that are not relevant for the given purpose. Once the simpler problem is solved, then the omitted details can be taken into consideration to solve the next lower level abstraction, and so on. Course Module  CS-6209 Software Engineering 1 2 Week 1: The Scope of Software Engineering Abstraction is a powerful way of reducing the complexity of the problem. The other approach to tackle problem complexity is DEPT OF CSE & IT VSSUT, Burla decomposition. In this technique, a complex problem is divided into several smaller problems and then the smaller problems are solved one by one. However, in this technique any random decomposition of a problem into smaller parts will not help. The problem has to be decomposed such that each component of the decomposed problem can be solved independently and then the solution of the different components can be combined to get the full solution. A good decomposition of a problem should minimize interactions among various components. If the different sub components are interrelated, then the different components cannot be solved separately and the desired reduction in complexity will not be realized. Need of Software Engineering The need of software engineering arises because of higher rate of change in user requirements and environment on which the software is working.  Large software - It is easier to build a wall than to a house or building, likewise, as the size of software become large engineering has to step to give it a scientific process.  Scalability - If the software process were not based on scientific and engineering concepts, it would be easier to re-create new software than to scale an existing one.  Cost- As hardware industry has shown its skills and huge manufacturing has lower down the price of computer and electronic hardware. But the cost of software remains high if proper process is not adapted.  Dynamic Nature- The always growing and adapting nature of software hugely depends upon the environment in which the user works. If the nature of software is always changing, new enhancements need to be done in the existing one. This is where software engineering plays a good role.  Quality Management- Better process of software development provides better and quality software product. Characteristics of Good Software A software product can be judged by what it offers and how well it can be used. This software must satisfy on the following grounds:  Operational  Transitional  Maintenance This tells us how well software works in operations. It can be measured on:  CS-6209 Software Engineering 1 3 Week 1: The Scope of Software Engineering  Budget  Usability  Efficiency  Correctness  Functionality  Dependability  Security  Safety Transitional This aspect is important when the software is moved from one platform to another  Portability  Interoperability  Reusability  Adaptability  Maintenance This aspect briefs about how well software has the capabilities to maintain itself in the ever-changing environment:  Modularity  Maintainability  Flexibility  Scalability In short, Software engineering is a branch of computer science, which uses well- defined engineering concepts required to produce efficient, durable, scalable, in- budget and on-time software products Software engineering diversity Software engineering is a systematic approach to the production of software that takes into account practical cost, schedule, and dependability issues, as well as the needs of software customers and producers. How this systematic approach is actually implemented varies dramatically depending on the organization developing the software, the type of software, and the people involved in the development process. There are no universal software engineering methods and techniques that are suit-able for all systems and all companies. Rather, a diverse set of software engineering methods and tools has evolved over the past 50 years. Perhaps the most significant factor in determining which software engineering methods and techniques are most important is the type of application that is being developed. There are many different types of application including: Course Module CS-6209 Software Engineering 1 4 Week 1: The Scope of Software Engineering 1. Stand-alone applications. These are application systems that run on a local computer, such as a PC. They include all necessary functionality and do not need to be connected to a network. Examples of such applications are office applications on a PC, CAD programs, photo manipulation software, etc. 2. Interactive transaction-based applications. These are applications that execute on a remote computer and that are accessed by users from their own PCs or terminals. Obviously, these include web applications such as e-commerce applications where you can interact with a remote system to buy goods and services. This class of application also includes business systems, where a business provides access to its systems through a web browser or special-purpose client program and cloud- based services, such as mail and photo sharing. Interactive applications often incorporate a large data store that is accessed and updated in each transaction. 3. Embedded control systems. These are software control systems that control and manage hardware devices. Numerically, there are probably more embedded systems than any other type of system. Examples of embedded systems include the software in a mobile (cell) phone, software that controls anti-lock braking in a car, and software in a microwave oven to control the cooking process. 4. Batch processing systems. These are business systems that are designed to process data in large batches. They process large numbers of individual inputs to create corresponding outputs. Examples of batch systems include periodic billing systems, such as phone billing systems, and salary payment systems. 5. Entertainment system. These are systems that are primarily for personal use and which are intended to entertain the user. Most of these systems are games of one kind or another. The quality of the user interaction offered is the most important distinguishing characteristic of entertainment systems. 6. Systems for modeling and simulation. These are systems that are developed by scientists and engineers to model physical processes or situations, which include many, separate, interacting objects. These are often computationally intensive and require high-performance parallel systems for execution. 7. Data collection systems. These are systems that collect data from their environment using a set of sensors and send that data to other systems for processing. The software has to interact with sensors and often is installed in a hostile environment such as inside an engine or in a remote location.  CS-6209 Software Engineering 1 5 Week 1: The Scope of Software Engineering 8. Systems of systems. These are systems that are composed of a number of other software systems. Some of these may be generic software products, such as a spreadsheet program. Other systems in the assembly may be specially written for that environment. Of course, the boundaries between these system types are blurred. If you develop a game for a mobile (cell) phone, you have to take into account the same constraints (power, hardware interaction) as the developers of the phone software. Batch processing systems are often used in conjunction with web- based systems. For example, in a company, travel expense claims may be submitted through a web application but processed in a batch application for monthly payment. You use different software engineering techniques for each type of system because the software has quite different characteristics. For example, an embedded control system in an automobile is safety-critical and is burned into ROM when installed in the vehicle. It is therefore very expensive to change. Such a system needs very extensive verification and validation so that the chances of having to recall cars after sale to fix software problems are minimized. User interaction is minimal (or perhaps nonexistent) so there is no need to use a development process that relies on user interface prototyping. For a web-based system, an approach based on iterative development and delivery may be appropriate, with the system being composed of reusable components. However, such an approach may be impractical for a system of systems, where detailed specifications of the system interactions have to be specified in advance so that each system can be separately developed. Nevertheless, there are software engineering fundamentals that apply to all types of software system: 1. They should be developed using a managed and understood development process. The organization developing the software should plan the development process and have clear ideas of what will be produced and when it will be completed. Of course, different processes are used for different types of software. 2. Dependability and performance are important for all types of systems. Software should behave as expected, without failures and should be available for use when it is required. It should be safe in its operation and, as far as possible, should be secure against external attack. The system should perform efficiently and should not waste resources. Course Module  CS-6209 Software Engineering 1 6 Week 1: The Scope of Software Engineering 3. Understanding and managing the software specification and requirements (what the software should do) are important. You have to know what different customers and users of the system expect from it and you have to manage their expectations so that a useful system can be delivered within budget and to schedule. 4. You should make as effective use as possible of existing resources. This means that, where appropriate, you should reuse software that has already been developed rather than write new software. These fundamental notions of process, dependability, requirements, management, and reuse are important themes of this book. Different methods reflect them in different ways but they underlie all professional software development. You should notice that these fundamentals do not cover implementation and programming. I don’t cover specific programming techniques in this book because these vary dramatically from one type of system to another. For example, a scripting language such as Ruby is used for web-based system programming but would be completely inappropriate for embedded systems engineering. Software engineering ethics Like other engineering disciplines, software engineering is carried out within a social and legal framework that limits the freedom of people working in that area. As a software engineer, you must accept that your job involves wider responsibilities than simply the application of technical skills. You must also behave in an ethical and morally responsible way if you are to be respected as a professional engineer. It goes without saying that you should uphold normal standards of honesty and integrity. You should not use your skills and abilities to behave in a dishonest way or in a way that will bring disrepute to the software engineering profession. However, there are areas where standards of acceptable behavior are not bound by laws but by the more tenuous notion of professional responsibility. Some of these are: 1. Confidentiality. You should normally respect the confidentiality of your employers or clients irrespective of whether or not a formal confidentiality agreement has been signed.  CS-6209 Software Engineering 1 7 Week 1: The Scope of Software Engineering 2. Competence. You should not misrepresent your level of competence. You should not knowingly accept work that is outside your competence. 3. Intellectual property rights. You should be aware of local laws governing the use of intellectual property such as patents and copyright. You should be careful to ensure that the intellectual property of employers and clients is protected. 4. Computer misuse. You should not use your technical skills to misuse other people’s computers. Computer misuse ranges from relatively trivial (game playing on an employer’s machine, say) to extremely serious (dissemination of viruses or other malware). Software Engineering Code of Ethics and Professional Practice ACM/IEEE-CS Joint Task Force on Software Engineering Ethics and Professional Practices PREAMBLE The short version of the code summarizes aspirations at a high level of the abstraction; the clauses that are included in the full version give examples and details of how these aspirations change the way we act as software engineering professionals. Without the aspirations, the details can become legalistic and tedious; without the details, the aspirations can become high sounding but empty; together, the aspirations and the details form a cohesive code. Software engineers shall commit themselves to making the analysis, specification, design, development, testing and maintenance of software a beneficial and respected profession. In accordance with their commitment to the health, safety and welfare of the public, software engineers shall adhere to the following Eight Principles: PUBLIC — Software engineers shall act consistently with the public interest. CLIENT AND EMPLOYER — Software engineers shall act in a manner that is in the best interests of their client and employer consistent with the public interest. PRODUCT — Software engineers shall ensure that their products and related modifications meet the highest professional standards possible. Course Module CS-6209 Software Engineering 1 8 Week 1: The Scope of Software Engineering JUDGMENT — Software engineers shall maintain integrity and independence in their professional judgment. MANAGEMENT — Software engineering managers and leaders shall subscribe to and promote an ethical approach to the management of software development and maintenance. PROFESSION — Software engineers shall advance the integrity and reputation of the profession consistent with the public interest. COLLEAGUES — Software engineers shall be fair to and supportive of their colleagues. SELF — Software engineers shall participate in lifelong learning regarding the practice of their profession and shall promote an ethical approach to the practice of the profession. Professional societies and institutions have an important role to play in setting ethical standards. Organizations such as the ACM, the IEEE (Institute of Electrical and Electronic Engineers), and the British Computer Society publish a code of professional conduct or code of ethics. Members of these organizations undertake to follow that code when they sign up for membership. These codes of conduct are generally concerned with fundamental ethical behavior. Professional associations, notably the ACM and the IEEE, have cooperated to produce a joint code of ethics and professional practice. This code exists in both a short form, shown in Figure 1.3, and a longer form (Gotterbarn et al., 1999) that adds detail and substance to the shorter version. The rationale behind this code is summarized in the first two paragraphs of the longer form: Computers have a central and growing role in commerce, industry, government, medicine, education, entertainment and society at large. Software engineers are those who contribute by direct participation or by teaching, to the analysis, specification, design, development, certification, maintenance and testing of software systems. Because of their roles in developing software systems, software engineers have significant opportunities to do good or cause harm, to enable others to do good or cause harm, or to influence others to do good or cause harm. To ensure, as much as possible, that their efforts will be used for good, software engineers must commit themselves to making software engineering a beneficial and respected profession. In accordance with that commitment, software engineers shall adhere to the following Code of Ethics and Professional Practice.  CS-6209 Software Engineering 1 9 Week 1: The Scope of Software Engineering The Code contains eight Principles related to the behaviour of and decisions made by professional software engineers, including practitioners, educators, managers, supervisors and policy makers, as well as trainees and students of the profession. The Principles identify the ethically responsible relationships in which individuals, groups, and organizations participate and the primary obligations within these relationships. The Clauses of each Principle are illustrations of some of the obligations included in these relationships. These obligations are founded in the software engineer’s humanity, in special care owed to people affected by the work of software engineers, and the unique elements of the practice of software engineering. The Code prescribes these as obligations of anyone claiming to be or aspiring to be a software engineer. In any situation where different people have different views and objectives you are likely to be faced with ethical dilemmas. For example, if you disagree, in principle, with the policies of more senior management in the company, how should you react? Clearly, this depends on the particular individuals and the nature of the dis-agreement. Is it best to argue a case for your position from within the organization or to resign in principle? If you feel that there are problems with a software project, when do you reveal these to management? If you discuss these while they are just a suspicion, you may be overreacting to a situation; if you leave it too late, it may be impossible to resolve the difficulties. Such ethical dilemmas face all of us in our professional lives and, fortunately, in most cases they are either relatively minor or can be resolved without too much difficulty. Where they cannot be resolved, the engineer is faced with, perhaps, another problem. The principled action may be to resign from their job but this may well affect others such as their partner or their children. A particularly difficult situation for professional engineers arises when their employer acts in an unethical way. Say a company is responsible for developing a safety-critical system and, because of time pressure, falsifies the safety validation records. Is the engineer’s responsibility to maintain confidentiality or to alert the customer or publicize, in some way, that the delivered system may be unsafe? The problem here is that there are no absolutes when it comes to safety. Although the system may not have been validated according to predefined criteria, these criteria may be too strict. The system may actually operate safely throughout its lifetime. It is also the case that, even when properly validated, the system may fail and cause an accident. Early disclosure of problems may result in damage to the employer and other employees; failure to disclose problems may result in damage to others. Course Module CS-6209 Software Engineering 1 10 Week 1: The Scope of Software Engineering You must make up your own mind in these matters. The appropriate ethical position here depends entirely on the views of the individuals who are involved. In this case, the potential for damage, the extent of the damage, and the people affected by the damage should influence the decision. If the situation is very dangerous, it may be justified to publicize it using the national press (say). However, you should always try to resolve the situation while respecting the rights of your employer. Another ethical issue is participation in the development of military and nuclear systems. Some people feel strongly about these issues and do not wish to participate in any systems development associated with military systems. Others will work on military systems but not on weapons systems. Yet others feel that national security is an overriding principle and have no ethical objections to working on weapons systems. In this situation, it is important that both employers and employees should make their views known to each other in advance. Where an organization is involved in military or nuclear work, they should be able to specify that employees must be willing to accept any work assignment. Equally, if an employee is taken on and makes clear that they do not wish to work on such systems, employers should not put pressure on them to do so at some later date. The general area of ethics and professional responsibility is becoming more important as software-intensive systems pervade every aspect of work and everyday life. It can be considered from a philosophical standpoint where the basic principles of ethics are considered and software engineering ethics are discussed with reference to these basic principles. This is the approach taken by Laudon (1995) and to a lesser extent by Huff and Martin (1995). Johnson’s text on computer ethics (2001) also approaches the topic from a philosophical perspective. However, I find that this philosophical approach is too abstract and difficult to relate to everyday experience. I prefer the more concrete approach embodied in codes of conduct and practice. I think that ethics are best discussed in a software engineering context and not as a subject in their own right. In this book, therefore, I do not include abstract ethical discussions but, where appropriate, include examples in the exercises that can be the starting point for a group discussion on ethical issues.  CS-6209 Software Engineering 1 11 Week 1: The Scope of Software Engineering References and Supplementary Materials Books and Journals 1. SOFTWARE ENGINEERING, 9th Edition; Ian Sommerville Online Supplementary Reading Materials 1. Fundamentals of Software Engineering; https://www.academia.edu/2586877/Lecture_01_Fundamentals_of_Software_Engine ering; October 14, 2019 2. Introduction to Software Engineering; https://en.wikibooks.org/wiki/Introduction_to_Software_Engineering; October 14, 2019 Online Instructional Videos Course Module