CSC/ECE 517 Fall 2007/wiki2 9 A3

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

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 This website provides a simple example on how the principle of least astonishment is applied in user interface design, programming language design, and ergonomics.

• User-Friendly Programming This website discusses about style that one can use to include various functionality that determines how a program will look when it is used. Some good examples can be found at this site.

• Yield In this website, the author demonstrates the principle of least astonishment by giving a simple example of how to declare a template in the Rails layout section.

Websites with examples of applications where the principle should be used

• Finding the Signal in the Noise This website quotes 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.

• HtmlUnit In this website the author mentions about how he is using HtmlUnit to parse and interpret HTML web pages. He also claims that HtmlUnit violates the principle of least surprise.

• Verification Through the Principle of Least Astonishment This website gives a link to research paper which proposes a new verification methodology inspired by the principle of least astonishment. It talks about an idea to provide an automatic assessment of what constitutes "common behaviour" for a system and uses this to detect any anomaly in the design.

• How to design Good APIs In this website, the author mentions about how to design good APIs and why they matter.

• Button on Visual browsers In this website, the author mentions about how one can improve his websites. He mentions that users visits the website with some expectations, and they develop new expectations as they use the page. So one should try to meet those expectations, and try to avoid surprising them. One shpuld keep an eye out for things that could be easily misunderstood, and keep an eye out for people who haven't seen the page yet; their mistakes may reveal a design flaw you haven't seen yet.

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://www.canonical.org/~kragen/tao-of-programming.html#book4 http://www.cs.arizona.edu/projects/sumatra/hallofshame
http://www.ibm.com/developerworks/library/us-cranky10.html?dwzone=usability
http://ergo.human.cornell.edu/ahtutorials/interface.html
http://doodleplex.com/glassmaze/2004/10/
http://mail.gnome.org/archives/evolution-list/2007-January/msg00202.html
http://ken.coar.org/burrow/index?month=2003-09#597
http://www.mssu.edu/seg-vm/bio_t__r__lafehr.html
http://blogs.sun.com/swinger/entry/simple_kisses_and_surprises
http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/52411
http://wiki.castleproject.org/index.php/MonoRail:Brail#Principle_of_Least_Surprise
http://larrytheliquid.com/

References

[1] http://www.faqs.org/docs/artu/ch11s01.html
[2] http://c2.com/cgi/wiki?PrincipleOfLeastAstonishment