Finkelstein, A.

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1 of 5Software EngineeringSoftware engineering is the branch of systems engineering concerned with the development of large andcomplex software intensive systems. It focuses on: the real-world goals for, services provided by, andconstraints on such systems; the precise specification of system structure and behaviour, and theimplementation of these specifications; the activities required in order to develop an assurance that thespecifications and real-world goals have been met; the evolution of such systems over time and acrosssystem families. It is also concerned with the processes, methods and tools for the development ofsoftware intensive systems in an economic and timely manner.The scientific and mathematical foundations of software engineering are derived from computer scienceand to a lesser extent systems science and control theory. It draws on engineering methods from otherdisciplines notably electronic and mechanical systems. The professional practice of software engineeringis carried out by software engineers, who are qualified by virtue of experience, training and education.Ideally these are certified or otherwise approved by an appropriate professional body.There are no satisfactory taxonomies of software engineering concerns. Rather there have grown up adiverse set of overlapping interests generally recognised by practitioners and researchers as areas ofsignificant importance.There are however, two main facets through which these interests can be viewed — process and product.Process is concerned with the organised set of tasks that a software engineer must carry out in order todevelop a system. It is concerned with the nature of the tasks, how they are configured into an overallcoherent workflow, the means by which these tasks are coordinated and environments that arenecessary to support this process. By contrast product is concerned with the artefacts that are producedduring a software development process, how they are represented, how they can be analysed and howkey properties can be assured and the tools required to achieve this.These two facets are best considered through an example. Establishing the requirements of users andother stakeholders in the development of a software intensive system is a major interest of softwareengineers. A large proportion of software development cost is attributable to this, it is a majordeterminant of system quality, errors associated with misunderstanding of requirements becomeincreasingly, indeed exponentially, expensive to fix as development proceeds. This concern is known as’requirements engineering’.Specialists in requirements engineering are interested in processes for gathering, interpreting andmanaging requirements-related information. They are further concerned with how these processes fitwith a larger software or system development process. Thus they are interested in how requirementsrelate to design, implementation, testing and so on. This is distinct from an interest in the products ofrequirements engineering, for example the representation of requirements-related information, usingpurpose-built specification languages and similar, and reasoning about this information to establishproperties such as consistency, completeness and so on.The major areas of software engineering interest are:requirements engineering — gathering, interpreting and managing requirements-relatedinformation, including the validation of that information with the stakeholders;software architecture — building structural descriptions of complex software-intensive system interms of components, connectors and configurations of components and connectors;2 of 5software analysis — determination of critical properties of a software-intensive systems throughthe analysis of abstract models of their structure and behaviour, including verification of therelationships between such models;software design — realising software architectures in terms of appropriate algorithms, programand data structures;testing — supporting quality assurance through the dynamic analysis of the behaviour of theproducts of the software development process;reverse engineering — the analysis of a software-intensive system to extract and create systemabstractions and design information;software maintenance and evolution — the control and management of modifications intended toensure continued or improved operation in the context of changing environment;reuse — the systematic reuse of knowledge gained during the software development process andartefacts ranging from requirements to program code during the development of subsequentsystems or members of a product family;formal specification — the use of representation schemes derived from discrete mathematics andlogic to specify and construct large and complex software intensive systems;middleware — the disciplined deployment of services derived from the software layer built abovethe network operating system to support the coordination of distributed software systems;software reliability and dependability — engineering software-intensive systems to achieveproperties related to the level of trust that users can have in the systems performing as required;performance — engineering software-intensive systems to achieve properties related to the timedependent behaviour of those systems, particularly performance estimation and the relationshipof the results of performance analysis to design models;software safety — engineering software-intensive systems so as to avoid safety being compromisedby the system entering dangerous states, particularly those in which failure may cause injury ordeath to human being;real-time — engineering software-intensive systems which are required to respond to externalevents within a given, generally small, interval of time;security engineering — engineering software-intensive systems where both the process must becarried out and the product must operate in the presence of potential adversaries;mobility — engineering software-intensive systems in the context of unstable structures impliedby physical mobility (mobile phones, PDAs, wireless networks) and logical mobility (mobilecode, agents);user-centered software engineering — engineering software-intensive systems where interactionwith human users forms a critical component, particularly the integration of user interface designconcerns within a broader software engineering process;3 of 5software configuration management — managing and controlling the products of the softwaredevelopment process, particularly managing the integrity of that information during systemevolution;software engineering tools and environments — developing automated support for softwaredevelopment tasks and frameworks through which such automated support can interoperate tounderpin coherent processes;software economics — engineering software-intensive systems with respect to value, cost andbenefits, particularly the practical means for, and theoretical underpinnings of, allocating scarcedevelopment resources;software metrics — the use of measurement of both products and process to control software-intensive development and to support decision making and risk management;quality management — the organisation of management and technical systems for determining andassuring the conformance of the products of software development to their requirements.Across all these areas there are a number of thematic topics that are worthy of note. Most significant ofthese are:software engineering education and training — the development of curricula, materials andprogrammes for training and education in software engineering principles and practices;software engineering professionalism — the development of a professional ethos, accreditationscheme and ethics for software engineers;software engineering research methodology — the identification of appropriate researchmethodologies to support validation of the findings of software engineering, notably thecombined use of observation, experiment, case-study and mathematical proof.The findings of software engineering are delivered in a variety of ways primarily through processes,languages and tools. More rarely these findings are raised to the level of general principles applying tothe engineering of classes of software system. The characteristic mode of delivery of softwareengineering findings is the software engineering method (commonly, though erroneously, methodology)an organised package of process, languages and heuristics derived from experience. The use ofengineering standards as a means of delivering guidance on good practice forms a useful baseline.It is very difficult to summarise the overall state-of-the-art in software engineering in a short space. Thereader interested in a general introduction should refer to the many excellent textbooks that areavailable. Best known, and a good starting point, are [6], [4] and [3], all of which are reasonably up todate. [1] affords a good start to the broader literature. The research literature on software engineering isreadily available. IEEE Transactions on Software Engineering (IEEE-TSE) and ACM Transactions onSoftware Engineering and Methodology (ACM-TOSEM) are the principal archival journals. There are alarge number of specialised journals including for example Automated Software Engineering (ASE),Requirements Engineering Journal (REJ), Software Process Journal (SPJ). IEEE Software plays animportant role in bridging between the ’pure’ research literature and practitioner-oriented articles. TheInternational Conference on Software Engineering (ICSE) is the flagship conference of the softwareengineering community; papers in this conference are generally of a high standard and the proceedingsreflect a broad view of research across software engineering. The European Software EngineeringConferences (ESEC) and the Foundations of Software Engineering Conferences (FSE), which are heldjointly in alternate years, are similar to ICSE though have tended historically to have a slightly more￿theoretical￿ orientation. There are a large number of specialised conferences and workshops ranging4 of 5from established meetings such as the International Workshop on Software Specification and Design,International Software Architecture Workshop, International Symposium on Software Testing andAnalysis to the ￿hot-topic￿ workshops held in conjunction with ICSE. There are excellent resources onthe web (links are provided on the web site associated with this volume). General software engineeringannouncements are distributed through the community-wide "seworld" mailing list.The context of software engineering is changing. Systems are rarely developed from scratch; mostsystem development involves extension of pre-existing systems and integration with ’legacy’infrastructure. These systems are embedded in complex, highly dynamic, decentralised organisations;they are required to support business and industrial processes which are continually reorganised to meetchanging consumer demands. The services that such a system provides must, for the life of the system,satisfy the requirements of a diverse and shifting group of stakeholders. There is a shift towards clientcentred approaches to development and an accompanying shift from a concern with whether a systemwill work towards how well it will work. Overall, fewer ’bespoke’ software systems are beingconstructed. Instead, generic components are built to be sold into markets. Components are selected andpurchased ’off the shelf’ with development effort being refocused on configuration and interoperability.The resulting systems are composed from autonomous, locally managed, heterogeneous components,which are required to cooperate to provide complex services. They are, in general, distributed and havesignificant non-functional constraints on their operation. There are a wide range of new, and constantlychanging business models relating to the provision of software and software-mediated services resultingfrom internet and e-commerce technology. The overall setting is characterised by on the one hand anincreasing business dependence on reliability of software infrastructure and on the other hand rapidchange and reconfiguration of business services necessitating rapid software development and frequentchange to that software infrastructure.Software engineering is addressing this changed context by focussing on a set of key challenges:Compositionality — When we compose components what effect does this have on the propertiesof those components? Can we reason about, and engineer for, the emergent properties of systemscomposed from components whose behaviour we understand?Change — How can we cope with requirements change? How can we build systems that are moreresilient or adaptive under change? How can we predict the effects of such changes?Non-functional Properties — How can we model non-functional properties of systems and reasonabout them, particularly in the early stages of system development? How can these models beintegrated with other models used in system development?Service-view — How can we shift from a traditional product-oriented view of software systemdevelopment towards a service view? What effects do new modes of software service deliveryhave on software development?Perspectives — How can we devise and support new structuring schemes and methods forseparating concerns in software engineering?Non-classical life cycles — How can we adapt conventional software engineering methods andtechniques to work in evolutionary, rapid, extreme and other non-classical styles of softwaredevelopment?Configurability — How can we allow users, in the broadest sense, to use components in order toconfigure, customize and evolve systems?5 of 5Domain specificity — How can we exploit the properties of particular domains(telecommunications, transport) to make any of these challenges easier to address?These overall software engineering challenges are not orthogonal and there are complex relationshipsbinding them together. Much of the most interesting recent work looks at these relationships. For anaccount of this see [2].Software engineering has delivered and is well set to continue to deliver both practical support tosoftware developers and the theoretical frameworks which will allow that practical support to beadopted, used and extended with confidence. Software engineering innovations take a surprisingly longtime to percolate through to every day use [5]. Despite this lag, current software engineering practice isbeing radically reshaped by object-oriented design methods, design tools with powerful code generation,testing and analysis environments, development patterns, incremental delivery based life-cycles,component models and document management environments, all the product of software engineering.A vision of the future of software engineering suggests a setting in which developers are able to wiretogether distributed components and services (heterogeneous and sourced over the net) havingestablished at an early stage, through rigorous (yet easy-to-use) formal analysis that the particularconfiguration will meet the requirements (both functional and non-functional). The overall process inwhich this takes place will have seamless tool support that extends through to change over the system orservice life. Each facet of the resulting system or service will be traceable to (and from) the originatingstakeholders who will be involved throughout the process.This vision is in fact an old one! The difference is that making it a reality is now within reach. Whatmakes software engineering exciting is that, in addition to the steady progress towards the vision, thereare also the discontinuities, such as was introduced in the last ten years by the web. The impact of suchmajor innovations cannot be predicted but they certainly offer wonderful new opportunities andchallenges.REFERENCES1. Dorfman, M. & Thayer, R.H. (Eds) Software Engineering, (November 1999), IEEE ComputerSociety.2. Finkelstein, A. (Ed) The Future of Software Engineering", (May 2000); ACM Press.3. Ghezzi, C. Jazayeri, M. & Mandrioli, D. Fundamentals of Software Engineering, (January1991), Prentice Hall.4. Pressman, R.S. Software Engineering: A Practitioner￿s, 4th edition (August 1996), McGraw HillCollege Div.5. Redwine S.T. & Riddle, W.E. Software Technology Maturation, Proceedings of the 8thInternational Conference on Software Engineering, 1985, pp 189- 200, IEEE Computer Society.6. Sommerville, I. Software Engineering (International Computer Science Series), 5th edition(November 1995) Addison-Wesley Pub Co.Anthony FinkelsteinUniversity College LondonJuly 10, 2000

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