CHAPTER 15 The ‘robust design’ William Kendall,USGS Colorado Cooperative Fish & Wildlife Research Unit Changes in population size through time are a function of. I am still getting mature as a software engineering/designer/architect, as you may want to call. At this point in time, I am getting small projects, private projects.

Contents • • • • • • • • • • Introduction [ ] In general, building robust systems that encompass every point of possible failure is difficult because of the vast quantity of possible inputs and input combinations. Since all inputs and input combinations would require too much time to test, developers cannot run through all cases exhaustively. Instead, the developer will try to generalize such cases.

Serial Number To Activate Steganos Internet Anonym 2012 Olympics on this page. For example, imagine inputting some. Some selected inputs might consist of a negative number, zero, and a positive number. When using these numbers to test software in this way, the developer generalizes the set of all reals into three numbers. This is a more efficient and manageable method, but more prone to failure. Generalizing test cases is an example of just one technique to deal with failure—specifically, failure due to invalid user input.

Systems generally may also fail due to other reasons as well, such as disconnecting from a network. Regardless, complex systems should still handle any errors encountered gracefully. There are many examples of such successful systems. Some of the most robust systems are evolvable and can be easily adapted to new situations.

Challenges [ ] Programs and software are tools focused on a very specific task, and thus aren't generalized and flexible. However, observations in systems such as the or demonstrate adaptation to their environments. One of the ways biological systems adapt to environments is through the use of redundancy. Many organs are redundant in humans.

The is one such example. Generally only need one kidney, but having a second kidney allows room for failure. This same principle may be taken to apply to software, but there are some challenges.

When applying the principle of redundancy to computer science, blindly adding code is not suggested. Blindly adding code introduces more errors, makes the system more complex, and renders it harder to understand. Code that doesn't provide any reinforcement to the already existing code is unwanted. The new code must instead possess equivalent [ ], so that if a function is broken, another providing the same function can replace it. To do so, the new code must know how and when to accommodate the failure point. This means more needs to be added to the system.