CSC/ECE 517 Fall 2007/wiki2 9 kk

Principle of Least Astonishment. Write a guide to the Web pages on the Principle of Least Astonishment. Which should the reader look at for easy-to-understand examples? Which give a feel for where the principle should be used? Is this principle present in fields other than programming? Is the term used consistently in other disciplines?

Principle of Least Astonishment

The principle of least astonishment states that when you are presented with different outcomes, one should always pick the outcome of least ambiguity or surprise. The principle has applications in a lot of fields. This wiki serves as a guide for the reader to understand more about this principle on the web. The principle of least astonishment goes by different names depending on the field of application like the element of least surprise, Occam's Razor etc.

Example

The simplest example is in programming where the name of a function does not indicate its functionality.

int add(int a, int b)
{
   return (a*a+b*b);
}

The function above is supposed to add two numbers and return the sum but actually returns the sum of squares of the two numbers which would surprise the programmer who is using it. Applying the principle of least astonishment, we can either rename the function to indicate its functionality or we can rewrite the functionality itself to correspond to its name.

int sum_of_squares(int a, int b)
{
   return (a*a+b*b);
}

or

int add(int a, int b)
{
   return a+b
}

The above example gives a feel for the principle of least astonishment. As this wiki is more about writing a guide to webpages on the principle of least astonishment, the next section talks about the applications of this principle, both in programming and in other fields by providing links to other pages on the web.

Applications in Programming

General Software Design

DDJ has an article which introduces the user to applying the principle of least surprise to general software design by using an example of using arrays in language called APL. A very basic introduction and some examples can also be found here.

API Design

The principle of least astonishment also plays an important role in API or library design. For example, when designing libraries or API's we want functions which does what the function name implies it will do. Steven's Tech Talk has a very good introduction to proper API design using the principle of least astonishment. Antonio Vierio looks at what makes an api a good api by applying the principle of least astonishment.

User interface design

The principle of least astonishment is used a lot in user interface design. Joel Spolsky has an article introducing user interface design using the principle of least astonishment. The article looks at a lot of examples of using the element of least surprise by comparing user interface design in Windows and Mac OS X.

A more general introduction to the application of the principle of least astonishment to UI design can be found here.

Webpage Design

Webpage design like UI design also finds the application of the principle of least astonishment. IBM has an excellent article on how this can be done.

Applications in Other Fields

The principle of least astonishment also finds a lot of applications in other fields though it might be referred to by a different name.

1. Occam's Razor is commonly used to explain phenonmena in such a way that the explanation makes the fewest assumptions possible. In other words, it can be paraphrased as "With all things being equal, the simplest solution tends to be the right one".

2. This paper looks at applying the principle of least astonishment to the verification of digital circuits.

3. This page looks at applying the principle of least astonishment to riding bicycles in traffic.

4. Wikipedia has some information on applying the principle of least astonishment to writing articles.

Other External Links

This section has links which do not fit in with the links already provided in the other sections.

Wikipedia entry on the principle of least astonishment

Tao of Programming

Principle of Least Astonishment in Ruby