The Essentials of Modern Software Engineering. Ivar Jacobson
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Название: The Essentials of Modern Software Engineering
Автор: Ivar Jacobson
Издательство: Ingram
Жанр: Программы
Серия: ACM Books
isbn: 9781947487260
isbn:
1.1 Beginning with Programming
The focus of our book is not about programming (see Sidebar 1.1), but about software engineering. However, understanding programming is an obvious place to start. Before we delve deeper into it, we should clarify the relation of programming to software development and to software engineering. Thus we have chosen the following.
• Programming stands for the work related to implementation or coding of source code.
• Software development is the larger process which, apart from programming, includes working with requirements, design, test, etc.
• “Software engineering combines engineering techniques with software development practices” (from Wikipedia). Moving from development to engineering means more reliance on science and less on craft, which typically manifests itself in some form of description of a designated way of working and higher-level automation of work. This allows for repeatability and consistency from project to project. Engineering also means that teams, for example, learn as they work and continuously improve their way of working. Thus, stated in simple terms, software engineering is bringing engineering discipline to software development.
Going forward, when introducing software engineering we will mean the larger subject of “software development + engineering,” implicitly understood without specifically separating out the two parts. This will be so even if in many cases the discussion is more about the development aspect, because the approach we take is chosen to facilitate the other aspect—engineering. When we sometimes talk about software development we want to be specific and refer to the work: the activities or the practices we use. We will not further try to distinguish these terms, so the reader can in many cases see them as synonyms.
As a frequent user of applications like Facebook, Google, Snapchat, etc., whether on his laptop or his mobile, Smith knew that software forms a major component in these products. From this, Smith became strongly interested in programming and enrolled in a programming course where he started to understand what program code was and what coding was all about. More importantly, he knew that programming was not easy. There were many things he had to learn.
The very first thing Smith learned was how to write a program that displays a simple “Hello World” on his screen, but in this case, we have a “Hello Essence!”, as in Figure 1.1. Through that he learned about programming languages, programming libraries, compilers, operating systems, processes and threads, classes, and objects. These are things in the realm of computer technology. We expect that you, through additional classes, will have learned about these things. We also expect you as a student to have some knowledge of these things as a prerequisite to reading this book. We expect that you have some knowledge of programming languages like Java and JavaScript.
Figure 1.1 Hello Essence.
1.2 Programming Is Not Software Engineering
However, Smith quickly learned that programming on its own is not software engineering. It is one thing to develop a small program, such as the “Hello Essence” program; it is a different thing to develop a commercial product.
It is true that some fantastic products such as those that gave birth to Apple, Microsoft, Facebook, Twitter, Google, and Spotify once were developed by one or a few individuals with a great vision but by just using programming as a skill. However, as the great vision has been implemented, be sure that these companies are today not relying on heroic programmers. Today, these companies have hired the top people with long experience in software engineering including great programming skills.
So, what is software engineering? Before we answer this question, we must first make it very clear that there is a remarkable difference between hacking versus professional programming. Professional programming involves clear logical thinking, beginning with the objective of the program, and refining the objective into logically constructed expressions. Indeed, the expressions are a reflection of the programmers’ thinking and analysis. Hacking on the other hand is an ad hoc trial and error to induce the desired effect. When the effect is achieved, the hacker marvels without really understanding why it worked. Professional programmers understand why and how it worked.
As such, professional programming is highly disciplined. Software engineering takes this discipline to software teams working on complex software. A typical software development endeavor involves more than one person working on a complex problem over a period of time to meet some objectives. Throughout Smith’s introductory software engineering course, he worked on several assignments, which frequently required him to work with his fellow students, and which included tasks, such as:
1. brainstorming what an event calendar app would look like;
2. writing code for a simple event calendar in a small group;
3. writing code for the event calendar app, and hosting the app on the cloud;
4. reviewing a given piece of code to find issues in it, for example bugs, and poor understandability; and
5. reviewing a fellow student’s code.
Through these assignments, Smith came to several conclusions. First, there is no one true way to write code for a given problem. Writing good quality code that fellow students can understand is not easy. It often takes more than one pair of eyes to get it working and comprehensible. He learned the following.
• Testing, i.e., checking that the program behaves as intended, is not easy. There are so many paths that executing the code can follow and all have to be tested.
• Agreeing on what the application would do was challenging. Even for that simple event calendar app, Smith and his team debated quite a while before they came to a consensus on what functionality ought to be available, and how the user interface should be laid out.
• A simple application may require multiple programming languages. For example, the event calendar app would need HTML5 and JavaScript for the front end, and the Java and SQL database for the backend. Consequently, Smith found that he had to spend a significant amount of time learning and getting familiar with new programming languages and new programming frameworks. Although he endeavored to learn about all these, it was certainly not easy with the limited time that was available.
• Time management is not easy because it is hard to estimate how much time each activity will require—or when to stop fine-tuning a certain piece of code to meet time constraints of the project.
As Smith was preparing for his industry internship interview, he tried to summarize on a piece of paper, from those things he then understood, what software engineering is about, and what he had learned thus far. Smith drew what he understood many times, and he observed that he couldn’t get it quite right. In the end, he settled for what is shown in Figure 1.2.
To Smith, software engineering was about taking some idea and forming a team according to the requirements. The team then transforms the requirements into a software product. To do this, the team engages in some kind of brainstorming, consensus, writing and СКАЧАТЬ