CSC/ECE 517 Fall 2007/wiki2 9 A3

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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 the result of performing some operation should be obvious, consistent, and predictable, based upon the name of the operation and other clues. This axiom states that you should do your utmost to write stuff that is not going to astonish, dismay, or confuse the next person who has to look at it later. When two elements of an interface conflict or are ambiguous, the behaviour should be that which will least surprise the human user or programmer at the time the conflict arises, because the least surprising behavior will usually be the correct one.

Example

The name of a function should reflect what it does. Otherwise, a user of the function will be unpleasantly surprised: [2]

Bad design:

int calculate_salary(int days, int perday)
{
  printf("The customer has worked for %d days and his salary per day is %d dollars", a, b);
}

Better design:

int calculte_salary(int days, int perday)
{
  return days * perday;
}

As can be seen in the example above, in the first example the name of the method and its functionality does not match. Whereas a better way of coding is the second one in which the functionality and the method name are related.

Guide to the Web pages on the Principle of Least Astonishment

After extensive search on 'Principle of Least Astonishment' on the web, we found almost every programming discipline follows this principle. Also there are many other disciplines that applies this principle. Here are our inferences about various websites that we went through.

Websites with simple examples

Simple examples can be found at the following sites:

  • User interface provides a simple example on how the principle of least astonishment is applied in user interface design, programming language design, and ergonomics.
  • API-Design mentions that the principle of least astonishment says that using a well-designed API should be as unsurprising as possible. An API that follows the principle of least surprise conforms to the consumer’s expectations.
  • Finding the Signal in the Noise mentions that principle of least astonishment idea is a good one most of the time. However, sometimes there is a good and simple reason for behavior that is surprising at first glance. In such cases, following the principle of least surprise may introduce extra complexity into the system and make its behavior more surprising in the long run.
  • Whidbey System.Configuration. In this website the author explains that how principle of least astonishment has become more of a guideline than a rule. He gives a good example of System Configuration in Visual Studio 2005.


In addition to function naming, the principle applies to user interface design. Menu items and other controls should have an effect that is obvious based upon their text labels and placement relative to other controls.

Principle of Least Astonishment in fields other than programming

Principle of Least Astonishment is a very common principle that is used in every day life.

Riding in Traffic

The principle of least astonishment can be translated as "ride predictably" i.e. riding in such a way that minimizes surprise. A complete article on it can be found at Riding in Traffic

Moon Walker

A very good article can be found at How Neil Armstrong brought the space program down to earth. On page 3, Armstrong mentions about principle of least astonishment.

Steens Mountain

A decade ago, Prévot and Coe (and colleagues) reported in three papers the evidence they had found of extremely rapid changes of the Earth’s magnetic field recorded in lava flows at Steens Mountain in southern Oregon (USA). The complete article can be found at Steens Mountain which describes how geomagnetists applied principle of least astonishment.

Guide to writing better articles

The Guide to writing better articles webpage gives advice on how to write an effective article. It includes material from a number of currently or formerly separate pages into an easy to consult overview. It states that when the principle of least astonishment is successfully employed, the information is apprehended by the reader without struggle. The average reader should not be shocked, surprised, or overwhelmingly confused by the article written. For complete article refer to the link provided.

Astrophysics

The Astrophysics webpage talks about works that involved Principle of Least Astonishment in Astrophysics.

See Also

http://doodleplex.com/glassmaze/2004/10/

References

[1] http://www.faqs.org/docs/artu/ch11s01.html
[2] http://c2.com/cgi/wiki?PrincipleOfLeastAstonishment
[3] http://www.cs.arizona.edu/projects/sumatra/hallofshame
[4] http://www.ibm.com/developerworks/library/us-cranky10.html?dwzone=usability
[5] http://ergo.human.cornell.edu/ahtutorials/interface.html

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