Lecture 1 - Software Engineering PDF

Software Engineering Lecture 01: Introduction Muhammad Haggag, Ph.D. Computer Science Department Faculty of Computers and Information Mansoura University Fall 2024 Course outline Chapter 1: Introduction Chapter 2: Software Processes Chapter 3:...

Software Engineering Lecture 01: Introduction Muhammad Haggag, Ph.D. Computer Science Department Faculty of Computers and Information Mansoura University Fall 2024 Course outline Chapter 1: Introduction Chapter 2: Software Processes Chapter 3: Agile Software Development Chapter 4: Requirements Engineering Chapter 5: System Modeling Chapter 6: Architectural Design Brief description of each chapter Chapter 1: Introduction Introduces software engineering, its significance, history, and key concepts. Explains the differences between software engineering and traditional engineering, emphasizing software quality and maintenance. Chapter 2: Software Processes Explores various software development processes and methodologies, such as the Waterfall model and iterative approaches. Discusses stages of development, including planning, coding, testing, and maintenance, highlighting the importance of a structured process. Chapter 3: Agile Software Development It explains key Agile frameworks, such as Scrum and Kanban, and discusses their principles and practices. The chapter highlights the benefits of Agile approaches, including faster delivery of features, responsiveness to change, and improved stakeholder engagement. 3 Brief description of each chapter Chapter 4: Requirements Engineering Examines the process of gathering, analyzing, and validating software requirements. Discusses techniques for eliciting functional and non- functional requirements, emphasizing clear documentation and stakeholder involvement. Chapter 5: System Modeling Covers modeling techniques used to represent software systems, particularly using UML. Discusses various diagrams (e.g., use case, class, sequence) that help visualize system architecture and behavior for better communication among stakeholders. Chapter 6: Architectural Design Focuses on defining the high-level structure of a software system. Discusses architectural patterns (e.g., layered architecture, microservices, client-server), and trade-offs, emphasizing the alignment of architecture with both functional and non-functional requirements for quality and scalability. 4 Topics covered Professional software development What is meant by software engineering. Case studies An introduction to three examples that are used in later chapters in the book. 5 Software engineering The economies of ALL developed nations are dependent on software. More and more systems are software controlled. Software engineering is concerned with theories, methods and tools for professional software development. Expenditure on software represents a significant fraction of the Gross National Product (GNP) in all developed countries. 6 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. 7 Software project failure Increasing system complexity As new software engineering techniques help us to build larger, more complex systems, the demands change. Systems have to be built and delivered more quickly; larger, even more complex systems are required; systems have to have new capabilities that were previously thought to be impossible. Failure to use software engineering methods It is fairly easy to write computer programs without using software engineering methods and techniques. Many companies have drifted into software development as their products and services have evolved. They do not use software engineering methods in their everyday work. Consequently, their software is often more expensive and less reliable than it should be. 8 Professional software development refers to the disciplined process of creating software applications that meet specific requirements and quality standards. 9 Frequently asked questions about software engineering Question 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 Software specification, software development, software engineering activities? validation and software evolution. What is the difference between software Computer science focuses on theory and fundamentals; engineering and computer science? software engineering is concerned with the practicalities of developing and delivering useful software. What is the difference between software System engineering is concerned with all aspects of engineering and system engineering? computer-based systems development including hardware, software and process engineering. Software engineering is part of this more general process. 10 Frequently asked questions about software engineering Question Answer What are the key challenges facing Coping with increasing diversity, demands for reduced software engineering? delivery times and developing trustworthy software. What are the costs of software Roughly 60% of software costs are development costs, engineering? 40% are testing costs. For custom software, evolution costs often exceed development costs. What are the best software engineering While all software projects have to be professionally techniques and methods? 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 The web has led to the availability of software services software engineering? 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. 11 Software products Generic products Stand-alone systems that are marketed and sold to any customer who wishes to buy them. Examples – PC software such as graphics programs, project management tools; CAD software; software for specific markets such as appointments systems for dentists. CAD (Computer-Aided Design) software is a type of application used for creating precise drawings, models, and designs in various fields, including engineering, architecture, and manufacturing. 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. Embedded control systems are specialized computing systems that are designed to perform dedicated functions within larger mechanical or electrical systems. They typically consist of hardware and software that work together to control devices and processes. 12 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. Example: Microsoft Office Suite 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. Example: Custom Enterprise Resource Planning (ERP) System 13 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 Software dependability includes a range of characteristics security 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. 14 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. Key Aspects of Software Engineering 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. 15 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. [Societal Impact] 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. [Cost of Changes] 16 Software process activities Software specification, where customers and engineers define the software that is to be produced and the constraints on its operation. Software development, where the software is designed and programmed. Software validation, where the software is checked to ensure that it is what the customer requires. Software evolution, where the software is modified to reflect changing customer and market requirements. 17 General issues that affect software Heterogeneity [diversity] 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. 18 General issues that affect software Security and trust As software is intertwined with all aspects of our lives, it is essential that we can trust that software. Scale Software has to be developed across a very wide range of scales, from very small embedded systems in portable or wearable devices through to Internet-scale, cloud-based systems that serve a global community. 19 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 and the background of the development team. 20 Application types Stand-alone applications [Microsoft Word] 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 [Online Banking Application] Applications that execute on a remote computer and are accessed by users from their own PCs or terminals. These include web applications such as e-commerce applications. Embedded control systems [Anti-Lock Braking System (ABS) in Vehicles] These are software control systems that control and manage hardware devices. Numerically, there are probably more embedded systems than any other type of system. 21 Application types Batch processing systems [Payroll Processing System] 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 [Smart TV] These are systems that are primarily for personal use and which are intended to entertain the user. Systems for modelling and simulation [Flight Simulator] These are systems that are developed by scientists and engineers to model physical processes or situations, which include many, separate, interacting objects. 22 Application types Data collection systems [Survey and Feedback Tools (e.g., SurveyMonkey)] These are systems that collect data from their environment using a set of sensors and send that data to other systems for processing. Systems of systems These are systems that are composed of a number of other software systems. Ex., Healthcare Information Systems Components: Electronic Health Records (EHRs): Store and manage patient medical histories and data. Laboratory Information Systems (LIS): Manage lab tests and results. Telemedicine Platforms: Enable remote consultations between patients and healthcare providers. 23 End of Lecture 01 2024-10-12 24 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. 25 Internet software engineering The Web is now a platform for running application and organizations are increasingly developing web-based systems rather than local systems. 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. 26 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. 27 Web software engineering Software reuse 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. Incremental and agile development 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. 28 Web software engineering Service-oriented systems [Loose Coupling] Software may be implemented using service-oriented software engineering, where the software components are stand-alone web services. Rich interfaces [Dynamic Content] Interface development technologies such as AJAX (Asynchronous JavaScript and XML) and HTML5 have emerged that support the creation of rich interfaces within a web browser. 29 Case studies 30 Case studies A personal insulin pump An embedded system in an insulin pump used by diabetics to maintain blood glucose control. A mental health case patient management system Mentcare. A system used to maintain records of people receiving care for mental health problems. 31 Insulin pump control system Collects data from a blood sugar sensor and calculates the amount of insulin required to be injected. Calculation based on the rate of change of blood sugar levels. Sends signals to a micro-pump to deliver the correct dose of insulin. Safety-critical system as low blood sugars can lead to brain malfunctioning, coma and death; high-blood sugar levels have long-term consequences such as eye and kidney damage. 32 Insulin pump hardware architecture 33 Activity model of the insulin pump Activity Models focus on the sequence of activities and interactions within a process. Data Flow Diagrams focus on the movement of data and its processing within a system. 34 Essential high-level requirements The system shall be available to deliver insulin when required. The system shall perform reliably and deliver the correct amount of insulin to counteract the current level of blood sugar. The system must therefore be designed and implemented to ensure that the system always meets these requirements. 35 https://shorturl.at/nx6nD 36 Thank you 37