- The Paradox of Software Engineering
- The Modern Definition of Software Engineering
- Is Software Engineering a Good Choice for Your Project?
This chapter is from the book
This chapter is from the book
This chapter is from the book
The Modern Definition of Software Engineering
Over the last 30 years, the software engineering community has followed the path of applying mechanical metaphors to the software development process. Software engineering is now an accepted academic subject and an active research field for universities. The focus for software engineering projects is on a defined, repeatable approach as exemplified by the IEEE definition:
Software engineering is the application of a systematic, disciplined, quantifiable approach to development, operation, and maintenance of software; that is, the application of engineering to software.5
This systematic, disciplined, and quantifiable approach to software development has proved to be very effective at developing safety critical systems. The team that writes the software for the space shuttle, for example, used this approach and has managed to achieve an admirable defect rate.
The last three versions of the program—each 420,000 lines long—had just one error each. The last 11 versions of this software had a total of 17 errors. Commercial programs of equivalent complexity would have 5,000 errors.6
In the process, however, other process constraints had to be relaxed.
Money is not the critical constraint: The group's $35 million per year budget is a trivial slice of the NASA pie, but on a dollars-per-line basis, it makes the group among the nation's most expensive software organizations.7
This is an appropriate engineering trade-off. When lives are at stake, it makes sense to use whatever resources are needed to ensure that nothing goes wrong. But what about software development when the consequence of error is lower?
Good Enough Software—Software Engineering for the Masses
For some software, rapid development of feature-rich applications is what matters. The idea is that users will put up with errors in programs because they have so many useful features that are unobtainable elsewhere. As Edward Yourdon8 put it, "I'm going to deliver a system to you in six months that will have 5,000 bugs in it—and you're going to be very happy!"
Good enough software is a logical extension of the ideas of software engineering. It represents the engineering trade-off between resources, schedule, features, and defects. The space shuttle software is safety-critical, so it has to minimize defects, accepting the resulting schedule and resource demands. Commercial shrink-wrapped applications like word processors and Web browsers need lots of features that must be developed quickly. Resources are constrained by the need to make a profit, so the engineering trade-off is made to shrink the schedule by spending less time removing known defects. The idea is that for some kinds of known defects, it is not economic to take the time to remove them.