The Essentials of Modern Software Engineering. Ivar Jacobson
the interfaces needed to its surrounding components. Inside a component could be program and data, or classes and objects, scripts, or old code (often called legacy code) developed many years ago. Components are still the dominating metaphor behind most modern methods. An interesting development of components that has become very popular is microservices, which we will discuss in Part III.
Sidebar 2.1 Paradigm Shift in Detail
In more detail, this paradigm shift was inspired by a new programming metaphor—object-oriented programming—and the trigger was the new programming language Smalltalk. However, the key ideas behind Smalltalk were derived from an earlier programming language, Simula 67, that was released in 1967. Smalltalk and Simula 67 were fundamentally different from previous generations of programming languages in that the whole software system was a set of classes embracing its own data, instead of programs (subroutines, procedures, etc.) addressing data types in some data store. Execution of the system was carried out through the creation of objects using the classes as templates, and these objects interacted with one another through exchanging messages. This was in sharp contrast to the previous model in which a process was created when the system was triggered, and this process executed the code line by line, accessing and manipulating the concrete data in the data store. A decade later, around 1990, a complement to the idea of objects received widespread acceptance inspired, in particular, by Microsoft. We got components.
With components, a completely new family of methods evolved. The old methods with their practices were considered to be out of fashion and were discarded. What started to evolve were in many cases similar practices with some significant differences but with new terminology. In the early 1990s, about 30 different component methods were published. They had a lot in common, but it was almost impossible to find the commonalities since each method author created his/her own terminology.
In the second half of the 1990s, OMG (a standards body called Object Management Group) felt that it was time to at least standardize how to represent software drawings, namely notations used to develop software. This led to a task force being created to drive the development of a new standard. The work resulted in the Unified Modeling Language (UML; see Figure 2.4), which will be used later in the book. This development basically killed all methods other than the Unified Process (marketed under the name Rational Unified Process (RUP)). The Unified Process dominated the software engineering world around the year 2000. Again, a sad step, because many of the other methods had very interesting and valuable practices that could have been made available in addition to some of the Unified Process practices. However, the Unified Process became in fashion and everything else was considered out of fashion and more or less thrown out.
Figure 2.4 A diagram (in fact a Use-Case diagram) from the Unified Modeling Language standard.
Over the years, many more technical practices other than the ones supported by the 30 component methods arrived. More advanced architectural practices or sets of practices, e.g., for enterprise architecture (EA), service-oriented architecture (SOA), product-line architecture (PLA), and recently architecture practices for big data, the cloud, mobile internet, and the internet of things (IoT) evolved. At the moment, it is useful to see these practices as pointers to areas of software engineering interest at a high level of abstractio: suffice it to say that EA was about large information systems for, e.g., the finance industry; SOA was organizing the software as a set of possibly optional service packages; and PLA was the counterpart of EA but for product companies, e.g., in the telecom or defense industry. More important is to know that again new methodologies grew up as mushrooms around each one of these technology trends. With each new such trend method authors started over again and reinvented the wheel. Instead of “standing on the shoulders of giants,”5 they preferred to stand on another author’s toes. They redefined already adopted terminology and the methods war just continued.
2.2.2.3 The Agile Methods Era
The agile movement—often referred to just as agile—is now the most popular trend embraced by the whole world. Throughout the history of software engineering, experts have always been trying to improve the way software is being developed. The goal has been to compress timescales to meet the ever-changing business demands and realities. If agile were to have a starting date, one can pinpoint it to the time when 17 renowned industry experts came together and penned the words of the agile manifesto. We will present the manifesto in Part IV and how Essence contributes to agile. But for now, it suffices to say that agile involves a set of technical and people-related practices. Most important is that agile emphasizes an innovative mindset such that the agile movement continuously evolves its practices.
Agile has evolved the technical practices utilized with components. However, its success did not come from introducing many new technical practices, even if some new practices, such as continuous integration, backlog-driven development, and refactoring, became popular with agile. Continuous integration suggests that developers several times daily integrate their new code with the existing code base and verify it. Backlog-driven development means that the team keeps a backlog of requirement items to work with in coming iterations. We will discuss this practice in more detail when we discuss Scrum in Part III. Refactoring is to continuously improve existing code iteration by iteration.
Agile rather simplified what was already in use to assist working in an iterative style and providing releasable software over many smaller iterations, or sprints as Scrum calls them.
2.2.3 There Are People Practices
As strange as it may sound, the methods we employed in the early days did not pay much attention to the human factors. Everyone understood of course that software was developed by people, but very few books or papers were written about how to get people motivated and empowered in developing great software. The most successful method books were quite silent on the topic. It was basically assumed that in one way or the other this was the task of management.
However, this assumption changed dramatically with agile methods. Before, there was a high reliance on tools so that code could be automatically generated from design documents such as UML diagrams. Accordingly, the role of programmers was downgraded, and other roles were more prestigious, such as project managers, analysts, and architects. With agile methods programming became reevaluated as a creative job. The programmers, the people who eventually created working software, were “promoted” and coding became again a prestigious task.
With agile many new practices evolved, for instance self-organizing teams, pair programming, and daily standups.
A self-organizing team includes members who are more generalists than specialists—most know how to code even if some are experts. It is like a soccer team—everyone knows how to kick the ball even if some are better at scoring goals and someone else is better at keeping the ball out of the goal.
Pair programming means that two programmers are working side-by-side developing the same piece of code. It is expected that the code quality is improved and that the total cost will be reduced. Usually one of the two, is more senior than the other, so this is also a way to improve team competency.
Daily standup is a practice intended to reduce impediments that team members have, as well as to retain motivation. Every morning the team meets for 15 min to go through each member’s situation: what he/she has done and what he/she will be doing. Any impediments are brought up but not addressed during the meeting. The issues will be discussed in separate meetings. This practice is part of the Scrum practice discussed in Part III.
Given the impact agile has had on the empowerment of programmers, it is easy to understand that agile has become very popular. Moreover, given the positive impact agile has had on our development of software, there