Software Engineers

"If a project has not achieved a system architecture, including its rationale, the project should not proceed to full-scale system development. Specifying the architecture as a deliverable enables its use throughout the development and maintenance process."

"What we see in both software development and military operations is a tendency for the pendulum to swing back and forth between extremes. Yet in most cases, we need a balance between armor and discipline and between mobility and agility. Actually, though, I would say that the leaders in both the agile and plan-driven camps occupy various places in the responsible middle. It’s only the over-enthusiastic followers who overinterpret “discipline” and “agility” to unhealthy degrees."

"Economic principles underlie the overall structure of the software lifecycle, and its primary refinements of prototyping, incremental development, and advancemanship. The primary economic driver of the life-cycle structure is the significantly increasing cost of making a software change or fixing a software problem, as a function of the phase in which the change or fix is made."

"Like many fields in their early stages, the software field has had its share of project disasters: the software equivalents of Beauvais Cathedral, the S.S. Titanic, and the "Galloping Gertie" Tacoma Narrows Bridge. The frequency of these disaster projects is a serious concern: a recent survey of 600 firms indicated that 35% of them had at least one "runaway' software project."

"The Code-and-Fix Model. The basic model used in the earliest days of software development contained two steps:"

"Poor management can increase software costs more rapidly than any other factor. Particularly on large projects, each of the following mismanagement actions has often been responsible for doubling software development costs."

"The dictionary defines "economics" as "a social science concerned chiefly with description and analysis of the production, distribution, and consumption of goods and services." Here is another definition of economics which I think is more helpful in explaining how economics relates to software engineering."

"A development method may be regarded as a path or a procedure by which the developer proceeds from a problem of a certain class to a solution of a certain class. In trivial cases, the method may be fully algorithmic; for example, there is an algorithmic procedure for obtaining the square root of a nonnegative number to any desired degree of accuracy."

"Agile development methodologies promise higher customer satisfaction, lower defect rates, faster development times and a solution to rapidly changing requirements. Plan-driven approaches promise predictability, stability, and high assurance. However, both approaches have shortcomings that, if left unaddressed, can lead to project failure. The challenge is to balance the two approaches to take advantage of their strengths and compensate for their weaknesses."

"Software Engineering Economics is an invaluable guide to determining software costs, applying the fundamental concepts of microeconomics to software engineering, and utilizing economic analysis in software engineering decision making."

"Systems engineering as an approach and methodology grew in response to the increase size and complexity of systems and projects. It "recognizes each system is an integrated whole even though composed of diverse, specialized structures and sub-functions..." (Chestnut, 1965) This engineering approach to the management of complexity by modularization was re-deployed in the software engineering discipline in the 1960s and 1970s with a proliferation of structured methodologies that enabled the the analysis, design and development of information systems by using techniques for modularized description, design and development of system components. Yourdon and DeMarco's Structured Analysis and Design, SSADM, James Martin's Information Engineering, and Jackson's Structured Design and Programming are examples from this era. They all exploited modularization to enable the parallel development of data, process, functionality and performance components of large software systems. The development of object orientation in the 1990s exploited modularization to develop reusable software. The idea was to develop modules that could be mixed and matched like Lego bricks to deliver to a variety of whole system specifications. The modularization and reusability principles have stood the test of time and are at the heart of modern software development."

"The beginning of wisdom for a programmer is to recognize the difference between getting his program to work and getting it right. A program which does not work is undoubtedly wrong; but a program which does work is not necessarily right. It may still be wrong because it is hard to understand; or because it is hard to maintain as the problem requirements change; or because its structure is different from the structure of the problem; or because we cannot be sure that it does indeed work."

"Success in all types of organization depends increasingly on the development of customized software solutions, yet more than half of software projects now in the works will exceed both their schedules and their budgets by more than 50%."

"Throughout the software life cycle, there are many decision situations involving limited resources in which software engineering economics techniques provide useful assistance."

"Practical knowledge of modularity has come largely from the computer industry. The term architecture was first used in connection with computers by the designers of the System/360: Gene M. Amdahl, Gerrit A. Blaauw, and Frederick P. Brooks."

"The term Computer Architecture was first defined in the paper by Amdahl, Blaauw and Brooks of International Business Machines (IBM) Corporation announcing IBM System/360 computer family on April 7, 1964. On that day IBM Corporation introduced, in the words of IBM spokesman, "the most important product announcement that this corporation has made in its history"."

"Blaauw... joined the IBM research lab at Poughkeepsie, New York, USA. During this period Blaauw became famous for his methodological manner of building computer machines. He made a difference between architecture, implementation and realization of a machine. After a couple of years working on some different machines, one of the most famous machines built by Frederick Brooks, Gerrit Blaauw and Gene Amdahl was the IBM System/360, which was introduced in 1964. IBM Board Chairman Thomas Watson, Jr. called the event the most important product announcement in the company's history."

"The design of a digital system starts with the specification of the architecture of the system and continues with its implementation and its subsequent realisation... the purpose of architecture is to provide a function. Once that function is established, the purpose of implementation is to give a proper cost-performance and the purpose of realisation is to build and maintain the appropriate logical organisation."

"A hardware design language should be (i) sufficiently high level, (ii) conversational, (iii) general purpose, and (iv) structured:"

"The result of the implementation, the logical design, is traditionally shown as a series of block diagrams. These blocks represent in effect a series of statements, Actually, a direct presentation of these statements is more suitable and, although less familiar, more easily understood. The Harvard Mark IV was to large degree designed and described by such statements, as has been the case with several subsequent developments."

"In computer design three levels can be distinguished: architecture, implementation and realisation; for the first of them, the following working definition is given: The architecture of a system can be defined as the functional appearance of the system to the user, its phenomenology."

"There always is an architecture, whether it is defined in advance - as with modern computers - or found out after the fact - as with many older computers. For architecture is determined by behavior, not by words. Therefore, the term architecture, which rightly implies the notion of the arch, or prime structure, should not be understood as the vague overall idea. Rather, the product of the computer architecture, the principle of operations manual, should contain all detail which the user can know, and sooner or later is bound to know."

"In this remarkable book on computer design, long-known in the field and widely used in manuscript form, Gerrit A. Blaauw and Frederick P. Brooks, Jr. provide a definitive guide and reference for practicing computer architects and for students. The book complements Brooks' recently updated classic, The Mythical Man-Month, focusing here on the design of "hardware" and there on "software," here on the "content" of computer architecture and there on the "process" of architecture design. The book's focus on "architecture" issues complements Blaauw's early work on "implementation" techniques. Having experienced most of the computer age, the authors draw heavily on their first-hand knowledge, emphasizing timeless insights and observations."

"By architecture I mean 'appearance to the user' - it is the functional specification of the system (its behavioural appearance). By implementation I mean 'internal logical organisation which performs the functions specified by the architecture' and by realisation I mean 'the physical components in which the logical organisation is embodied'."

"The purpose of the Committee was to study and report upon the desirability and characteristics of another computer system based on Stretch technology but having a lower cost and broader market than the 7000 Sigma system. The Committee was instructed to keep an open mind in initially examining various machine possibilities both from the engineering and marketing points of view..."

"The architecture of a system can be defined as the functional appearance of the system to the user."

"A study of the high-speed computer market with the intention of specifying a new computer brings forth a number of interesting observations... [An] striking feature of the market is that we seem to be close to satisfying the need for present-day uses of computers, but are standing on the threshold of a vast new area of applications. This new area can be characterized by the phrase computers which interact with the outside world. This concept is called "Integrated Data Processing", "Real-Time. Operation", "Process Control", "In-Line Operation", etc, Its characteristic feature is the ability of the computer to accept and send information directly to other devices. The use of computers in this fashion is being developed in the aircraft and missile industries . It is important to note that both scientific and commercial applications are going in this direction."

"The term architecture is used here to describe the attributes of a system as seen by the programmer, i.e., the conceptual structure and functional behavior, as distinct from the organization of the data flow and controls, the logical design, and the physical implementation. i. Additional details concerning the architecture,"

"[The architecture specification covers] all functions of the machine that are observable by the program."

"Scientific customers are traditionally less worried about reprogramming efforts than commercial customers, since many jobs are of a research nature and will be done over from time to time anyway. This is obviously true of many small and 'lone shot" problems. In practice, however, there are many more machine hours spent on production-type scientific problems than on those of research-type at most scientific computing installations. These production problems can be as rigid and static as any commercial job. The scientists responsible for production work will complain about reprogramming just as violently as an accountant will under the same circumstances."

"Blaauw and Brooks first develop a conceptual framework for understanding computer architecture. They then describe not only what present architectural practice is, but how it came to be so. A major theme is the early divergence and the later reconvergence of computer architectures. They examine both innovations that survived and became part of the standard computer, and the many ideas that were explored in real machines but did not survive. In describing the discards, they also address "why" these ideas did not make it"

"As usual the audience consisted mainly of professors of computing science; this time the speakers were mainly specialists in logic design: for many in the audience the exposure was a shock. At the level of component technology the change over the last fifteen years has been drastic: what used to be expressed in milliseconds is expressed in microseconds now, what used to be expressed in kilobucks is now expressed in dimes and quarters. This change has been so drastic that it is well-known. Much less known is that at the next levels, viz. of circuit design and logic design, the attention of the designers has been so fully usurped by the obligation to adapt to the ever changing technology, that at those levels design methodology has had no chance to mature from craft to scientific discipline. This is in sharp contrast to the developments in programming methodology, where during that period of fifteen years a fairly stable "base" could be enjoyed. Having witnessed that development in programming methodology at close quarters, I was overcome by the feeling of being exposed to the result of fifteen years of intellectual stagnation, and it was during Blaauw's lecture on the first afternoon that I asked my right-hand neighbour "Close your eyes, forget how you came here and guess in which year you are living."; without hesitation he came up with exactly the same year I had in mind: 1962."

"Systems engineering as an approach and methodology grew in response to the increase size and complexity of systems and projects... This engineering approach to the management of complexity by modularization was re-deployed in the software engineering discipline in the 1960s and 1970s with a proliferation of structured methodologies that enabled the the analysis, design and development of information systems by using techniques for modularized description, design and development of system components. Yourdon and DeMarco's Structured Analysis and Design, SSADM, James Martin's Information Engineering, and Jackson's Structured Design and Programming are examples from this era. They all exploited modularization to enable the parallel development of data, process, functionality and performance components of large software systems. The development of object orientation in the 1990s exploited modularization to develop reusable software. The idea was to develop modules that could be mixed and matched like Lego bricks to deliver to a variety of whole system specifications. The modularization and reusability principles have stood the test of time and are at the heart of modern software development."

"A new type of professional is emerging – the enterprise engineer"

"Enterprise Engineering is not a single methodology, but a sophisticated synthesis of the most important and successful of today's change methods. "Enterprise Engineering" first explains in detail all the critical disciplines (including continuous improvement, radical reinvention of business processes, enterprise redesign, and strategic visioning). It then illustrates how to custom-design the right combination of these change methods for your organization's specific needs."

"Enterprise engineering is an integrated set of disciplines for building an enterprise, its processes, and systems."

"Information engineering has been defined with the reference to automated techniques as follows: An interlocking set of automated techniques in which enterprise models, data models and process models are built up in a comprehensive knowledge-base and are used to create and maintain data-processing systems."

"From a very early age, we form concepts. Each concept is a particular idea or understanding we have about our world. These concepts allow us to make sense of and reason about the things in our world. These things to which our concepts apply are called objects."

"Information Engineering is the application of an interlocking set of formal techniques for the planning, analysis, design, and construction of information systems on the enterprise wide basis or across a major sector of the enterprise."

"A horrifying amount of "business engineering" is done with the wrong strategic vision. A horrifying amount of IT development is done with the wrong business design."

"A real-time computer system may be defined as one which controls an environment by receiving data, processing them, and taking action or returning results sufficiently quickly to affect the functioning of the environment at that time."

"Dr James Martin, entrepreneur, visionary, "guru of the information age", "father of Case", ranked fourth in the world by Computerworld among the most influential people in the computer industry, Martin is not only a distinguished technology expert, but also a leading business authority, generally acknowledged as THE specialist on the social and business implications of computers and technology."

"As technology grows in power, its ability either to disrupt or to heal increases. We can destroy the planet more easily than we can heal the harm we have done so far. To heal, we have to move to new technologies, new social patterns, new types of consumer products, new ways of generating and spending wealth. Such changes will inevitably occur, whether they are brought by healing forethought or mindless destruction. The future will not be a repetition of the past."

"For me, he has been an important pioneer in crucial areas throughout his career. Here are two examples:"

"In his article “CAD: A Statement of Objectives”, published in. 1960, Ross, who was thirty years old then, defined not only the term CAD, but also the principles, goals and visions of Computer Aided Design. His ideas shaped all the further CAD development in the past 50 years."

"Douglas T. Ross, who began his career as a graduate student in math at MIT where he was quickly lured into computing, serving as head of the Computer Applications Group from 1952 to 1969, when he left MIT to form SofTech, Inc., which he served as president until 1975 and since then as chairman. He's made seminal contributions to several areas of computing, ranging from automatic programming of numerically controlled tools, the computer language APT, through Computer Aided Design, his Automated Engineering Design System, down to software engineering, the method of structured analysis design technique, which he puts generally under the heading of man machine collaboration. He's an old hand at historical gatherings, having reported on APT at the conference on the History of Programming Languages held in 1978, and more recently on the early development in the History of Personal Workstations in 1986."

"Even though we started in the days when the equipment itself wasn't able to do very exciting visual things, we were always concentrating on this matter of communication and meaning."

"As Head of the Computer Application Group at the MIT Electronic Systems Laboratory, Doug led the development of the (APT), a special purpose programming language that became the world standard for programming computer-controlled machine tools. He then turned his attention to the development of a and supporting tools. This led to the development while at MIT of the first software engineering language and supporting tools, the AED system. In 1969 Doug founded where he continued to work on software engineering standards. While at SofTech, Doug conceived of SA, a graphic notation and methodology for system description. SA has been successfully applied worldwide as SofTechs (SADT) or as the U.S. government standard ."

"The first paper I ever wrote was "Gestalt Programming" and that was in 1955. The whole idea there was to replace the laborious writing out of detailed programs and all those steps by having analyzed a problem area well enough so that you had what I later came to call a "systematized solution." Then you could compose different problems of this class by just plugging together pieces of program, and they would in turn be controlled by a pushbutton language. The user would make a number of discreet selections. It's just like nowadays it's done with menus, and when you had indicated all the pieces that you wanted to put together--by these mnemonic names and words for things associated with buttons, switches, with one meaning "period," essentially, for that sentence, you see--all these things would be brought together and that would be the man/machine, manual-intervention mode of problem-solving. I took over the term from studying Gestalt psychology, meaning that everything was brought together at once, as a unit, instead of this laborious step-by-step build-up."

"A lot of people are not familiar with the fact that when Lincoln Lab grew out of the Project Whirlwind (which were just names to me at that point) for the purpose of looking into radar air defense -- processing radar signals with the computer and then using radio controls to defend with fighters and so forth -- Whirlwind had been originally designed as an aircraft simulator for individual airplanes."