This post originated from an RSS feed registered with Python Buzz by Jarno Virtanen. Original Post: Seven is not a magic number Feed Title: Python owns us Feed URL: http://sedoparking.com/search/registrar.php?domain=®istrar=sedopark Feed Description: A weblog about Python from the view point of Jarno Virtanen. Latest Python Buzz Posts Latest Python Buzz Posts by Jarno Virtanen Latest Posts From Python owns us

I don't think that you can refer to the classic paper about the limits of human cognition, The Magical Number Seven, Plus or Minus Two: ..., in the context of deciding how many elements should there be in a weblog entry. (I don't claim that he was being too serious with the reference, but anyway.)

First, in the light of more recent research the amount is closer to five items, plus minus two, which makes it four not seven.

Second, the number refers to the amount of chunks people are able to hold in their head without training, like repeating and such. This is called the working memory, or short-term memory. How exactly should this relate to the design decision of the amount of elements in weblog entry is not revealed. (Please, don't just say it's magic, because that is clearly not the case.)

Sure, there are times you need to work with the raw XML of a feed, when learning how to read or write them for example, but that still does not make the Miller's paper relevant. To make it relevant to the case you would have to describe how human's working memory would be constantly burdened with with too many elements (if the entry had for example eight elements).

In user interfaces in general this limitation means that you should not make users rely on their short-term memory. This occurs, for example, when the user interface has a dialog box that contains something that user has to remember in some other context, when the dialog box is no longer open. I cannot see any situation where I must memorize names of all the elements in a weblog entry without the possibility to see the other thing I am working on simultaneously. You know, one can for example tile windows so that you can see both the raw XML feed and the content managing system you're working on that will be producing the same stuff.

(Note: there might be other reasons for having less than seven elements in an entry. Reasons like simplicity or learnability.)