Chapter 1- Introduction

What is Software? The product that software professionals build and then support over the long term. Software encompasses: (1) instructions (computer programs) that when executed provide desired features, function, and performance; (2) data structures that enable the programs to adequately store and manipulate information and (3) documentation that describes the operation and use of the programs.

Why Software is Important? The economies of ALL developed nations are dependent on software. More and more systems are software controlled ( transportation, medical, telecommunications, military, industrial, entertainment,) Software engineering is concerned with theories, methods and tools for professional software development.

Software costs Software costs often dominate computer system costs. The costs of software on a PC are often greater than the hardware cost. Software costs more to maintain than it does to develop. For systems with a long life, maintenance costs may be several times development costs. Software engineering is concerned with cost-effective software development.

How It all Starts Every software project is arisen by some business need— the need to correct a defect in an existing application; the need to the need to adapt a ‘legacy system’ to a changing business environment; the need to the need to adapt a ‘legacy system’ to a changing technology; the need to extend the functions and features of an existing application, or the need to create a new product, service, or system.

Software types System Software Application Software Middleware Software ?

Stand-alone applications Application types 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. Interactive transaction-based applications Applications that execute on a remote computer and are accessed by users from their own PCs, terminals or other client devices. These include web applications such as e-commerce applications. Embedded control systems These are software control systems that control and manage hardware devices.

Batch processing systems Application types 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. Entertainment systems These are systems that are primarily for personal use and which are intended to entertain the user. Systems for modelling and simulation These are systems that are developed by scientists and engineers to model physical processes or situations, which include many, separate, interacting objects.

Data collection systems Application types 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. Business Intelligence systems Business intelligence (BI) is a technology-driven process for analyzing data and presenting actionable information to help corporate executives, business managers and other end users make more informed business decisions. Artificial Intelligence systems Systems of systems These are systems that are composed of a number of other software systems.

Software products Generic products Customized products Software systems that are marketed and sold to any customer who wishes to buy them. Examples – PC software such as editing, graphics programs, project management tools; CAD software; software for specific markets such as appointments systems for dentists. Customized products Software that is commissioned by a specific customer to meet their own needs. Examples – embedded control systems, air traffic control software, traffic monitoring systems.

Product specification Generic products The specification of what the software should do is owned by the software developer and decisions on software change are made by the developer. Customized products The specification of what the software should do is owned by the customer for the software and they make decisions on software changes that are required.

Frequently asked questions about software engineering Answer What is software? Computer programs and associated documentation. Software products may be developed for a particular customer or may be developed for a general market. What are the attributes of good software? Good software should deliver the required functionality and performance to the user and should be maintainable, dependable and usable. What is software engineering? Software engineering is an engineering discipline that is concerned with all aspects of software production. What are the fundamental software engineering activities? Software specification, software development, software validation and software evolution. What is the difference between software engineering and computer science? Computer science focuses on theory and fundamentals; software engineering is concerned with the practicalities of developing and delivering useful software. What is the difference between software engineering and system engineering? System engineering is concerned with all aspects of computer-based systems development including hardware, software and process engineering. Software engineering is part of this more general process.

Frequently asked questions about software engineering Answer What are the key challenges facing software engineering? Coping with increasing diversity, demands for reduced delivery times and developing trustworthy software. What are the costs of software engineering? Roughly 60% of software costs are development costs, 40% are testing costs. For custom software, evolution costs often exceed development costs. What are the best software engineering techniques and methods? While all software projects have to be professionally managed and developed, different techniques are appropriate for different types of system. For example, games should always be developed using a series of prototypes whereas safety critical control systems require a complete and analyzable specification to be developed. You can’t, therefore, say that one method is better than another. What differences has the web made to software engineering? The web has led to the availability of software services and the possibility of developing highly distributed service-based systems. Web-based systems development has led to important advances in programming languages and software reuse.

Essential attributes of good software Product characteristic Description Maintainability Software should be written in such a way so that it can evolve to meet the changing needs of customers. This is a critical attribute because software change is an inevitable requirement of a changing business environment. Dependability and security Software dependability includes a range of characteristics including reliability, security and safety. Dependable software should not cause physical or economic damage in the event of system failure. Malicious users should not be able to access or damage the system. Efficiency Software should not make wasteful use of system resources such as memory and processor cycles. Efficiency therefore includes responsiveness, processing time, memory utilisation, etc. Acceptability Software must be acceptable to the type of users for which it is designed. This means that it must be understandable, usable and compatible with other systems that they use.

Software Engineering: Definition Software Engineering is a collection of techniques, methodologies and tools that help with the production of a high quality software system with a given budget before a given deadline while change occurs. 20

Engineering discipline Software engineering Software engineering is an engineering discipline that is concerned with all aspects of software production from the early stages of system specification through to maintaining the system after it has gone into use. Engineering discipline Using appropriate theories and methods to solve problems bearing in mind organizational and financial constraints. All aspects of software production Not just technical process of development. Also project management and the development of tools, methods etc. to support software production.

Software engineering The goal is to produce high quality software to satisfy a set of functional and nonfunctional requirements. How do we do that? First, and foremost, by acknowledging that it is a problem solving activity. That is, it has to rely on well- known techniques that are used all over the world for solving problems.

Software engineering is a layered technology tools methods process model a “quality” focus Any engineering approach must rest on organizational commitment to quality which fosters a continuous process improvement culture. Process layer as the foundation defines a framework with activities for effective delivery of software engineering technology. Establish the context where products (model, data, report, and forms) are produced, milestone are established, quality is ensured and change is managed. Method provides technical how-to’s for building software. It encompasses many tasks including communication, requirement analysis, design modeling, program construction, testing and support. Tools provide automated or semi-automated support for the process and methods.

There are two major parts of any problem solving process: Software engineering There are two major parts of any problem solving process: Analysis: Understand the nature of the problem. This is done by looking at the problem and trying to see if there are sub aspects that can be solved independently from each other. This means, that we need to identify the pieces of the puzzle Synthesis: Once you have identified the pieces, you want to put them back together into a larger structure, usually by keeping some type of structure within the structure.

Software Engineering: A Problem Solving Activity For problem solving we use Techniques (methods): Formal procedures for producing results using some well- defined notation Methodologies: Collection of techniques applied across software development and unified by a philosophical approach Tools: Instrument or automated systems to accomplish a technique

Importance of software engineering More and more, individuals and society rely on advanced software systems. We need to be able to produce reliable and trustworthy systems economically and quickly. It is usually cheaper, in the long run, to use software engineering methods and techniques for software systems rather than just write the programs as if it was a personal programming project. For most types of system, the majority of costs are the costs of changing the software after it has gone into use.

General issues that affect most software Heterogeneity Increasingly, systems are required to operate as distributed systems across networks that include different types of computer and mobile devices. Business and social change Business and society are changing incredibly quickly as emerging economies develop and new technologies become available. They need to be able to change their existing software and to rapidly develop new software. Security and trust As software is intertwined ( wrap around ) with all aspects of our lives, it is essential that we can trust that software.

Software engineering diversity There are many different types of software system and there is no universal set of software techniques that is applicable to all of these. The software engineering methods and tools used depend on the type of application being developed, the requirements of the customer/generic software the background of the development team.

Software engineering fundamentals Some fundamental principles apply to all types of software system, irrespective of the development techniques used: Systems should be developed using a managed and understood development process. Of course, different processes are used for different types of software. Dependability and performance are important for all types of system. Understanding and managing the software specification and requirements (what the software should do) are important. Where appropriate, you should reuse software that has already been developed rather than write new software.

Symptoms of Software Development Problems These symptoms are readily observable in the real world. Just like in the medical world, it is not sufficient to treat the symptoms. One must address the root causes (as shown on the next page). An example of treating the symptoms is addressing the second bullet by insisting that no changes to requirements be accepted after a certain date. This is unrealistic. Change will happen to the business environment regardless, and the result may be that users reject the system that is built since it has not adapted to their changing needs. Encourage student interaction on this slide. One possibility is to ask students for symptoms of problems they have observed, before you show the slide. You could then compare the students’ list to this list. Or you could show the list first and ask for additional symptoms that students have observed. Inaccurate understanding of end-user needs Inability to deal with changing requirements Modules that don’t fit together (integration) Software that’s hard to maintain or extend (brittle) Late discovery of serious project flaws (integration) Poor software quality (architecture, risks unanticipated…) Process not responsive to Change (Gantt Charts…) Unacceptable software performance Team members in each other’s way, unable to reconstruct who changed what, when, where, why (software architecture, … and we could go on and on

Software engineering and the web The Web is now a platform for running application and organizations are increasingly developing web-based systems rather than local systems. Web services allow application functionality to be accessed over the web. Cloud computing is an approach to the provision of computer services where applications run remotely on the ‘cloud’. Users do not buy software buy pay according to use.

Web software engineering Software reuse is the dominant approach for constructing web-based systems. When building these systems, you think about how you can assemble them from pre-existing software components and systems. Web-based systems should be developed and delivered incrementally. It is now generally recognized that it is impractical to specify all the requirements for such systems in advance. User interfaces are constrained by the capabilities of web browsers. Technologies such as AJAX allow rich interfaces to be created within a web browser but are still difficult to use. Web forms with local scripting are more commonly used.

Web-based software engineering Web-based systems are complex distributed systems but the fundamental principles of software engineering discussed previously are as applicable to them as they are to any other types of system. The fundamental ideas of software engineering, apply to web-based software in the same way that they apply to other types of software system.

Software Myths - Management "We already have a book that is full of standards and procedures for building software. Won't that provide my people with everything they need to know?" Reality : The book of standards may very well exist, but is it used? Are software practitioners aware of its existence? Does it reflect modern software engineering practice? Is it complete? Is it adaptable? Is it streamlined to improve time to delivery while still maintaining a focus on Quality? In many cases, the answer to these entire question is no.

Software Myths - Management "If we get behind, we can add more programmers and catch up" Reality : Software development is not a mechanistic process like manufacturing. : “Adding people to a late software project makes it later.” At first, this statement may seem counterintuitive. However, as new people are added, people who were working must spend time educating the newcomers, thereby reducing the amount of time spent on productive development effort "If I decide to outsource the software project to a third party, I can just relax and let that firm build it" Reality : If an organization does not understand how to manage and control software project internally, it will invariably struggle when it out sources software project.

Software Myths - Customer "A general statement of objectives is sufficient to begin writing programs – we can fill in the details later" Ambiguous statement of objectives spells disaster "Project requirements continually change, but change can be easily accommodated because software is flexible" Impact of change depends on where and when it occurs in the software life cycle (requirements analysis, design, code, test)

Software Myths - Practitioner "Once we write the program and get it to work, our job is done" 60% to 80% of all effort expended on software occurs after it is delivered "Until I get the program running, I have no way of assessing its quality Formal technical reviews of requirements analysis documents, design documents, and source code (more effective than actual testing) Test-first approaches Prototyping to verify design and structure Prototyping to validate requirements 

Software Myths - Practitioner "The only deliverable work product for a successful project is the working program" Software, documentation, test drivers, test results Lots of documentation: installation guides, usage guides, maintenance guides, API definitions and examples 

Key points Software engineering is an engineering discipline that is concerned with all aspects of software production. Essential software product attributes are maintainability, dependability and security, efficiency and acceptability. The high-level activities of specification, development, validation and evolution are part of all software processes. The fundamental notions of software engineering are universally applicable to all types of system development.

Key points There are many different types of system and each requires appropriate software engineering tools and techniques for their development. The fundamental ideas of software engineering are applicable to all types of software system.

Members of Development Team Requirement analysts: work with the customers to identify and document the requirements Designers: generate a system-level description of what the system us supposed to do Programmers: write lines of code to implement the design Testers: catch faults Trainers: show users how to use the system Maintenance team: fix faults that show up later Librarians: prepare and store documents such as software requirements Configuration management team: maintain correspondence among various artifacts

Members of Development Team Project manager Business analysts Infrastructure administrators ( network , database , security , system …)

Software Engineering Careers Software engineer is a person who applies the principles of software engineering to the design, development, maintenance, testing, and evaluation of the software and systems that make computers or anything containing software work. A software developer is a person concerned with facets of the software development process, including the research, design, programming, and testing of computer software. There is no clear distinction between these careers. Sometimes may be identified as just coder , or experienced software engineer.

Software Engineering Careers General career titles for software engineering: software engineer software specialist software architect system analyst.... Software developer : software developer coder front-end , back-end coder …

Software Engineering Careers Software testing: software tester test specialist …

Software Engineer - Degree About half of all practitioners today have degrees in computer science, information systems, or information technology. A small, but growing, number of practitioners have software engineering degrees

Software Engineer – Other Degrees In business, some software engineering practitioners have MIS or computer information systems degrees. In embedded systems, some have electrical engineering, electronics engineering, computer science with emphasis in "embedded systems" or computer engineering degrees, because embedded software often requires a detailed understanding of hardware. In medical software, practitioners may have medical informatics, general medical, or biology degrees. Some practitioners have mathematics, science, engineering, or technology degrees. Some have philosophy (logic in particular) or other non-technical degrees And, others have no degrees

The Role of Software Engineer A bridge from customer needs to programming implementation Customer Software Engineering "You cannot solve it, unless you understand it." Software Developer First law of software engineering Software engineer is willing to learn the problem domain (problem cannot be solved without understanding it first)

The Role of Software Engineer

The slide mainly based on the Chapter 1 of Texbook Software Engineering , Sommerville . Chapter 1 Introduction