In the field of cognitive psychology there’s this so-called “Magic Number 7.” Basically, the idea is that humans can only keep 7 disjointed “things”, plus or minus two, in short-term memory at once. To see what I mean, study the following list of words for a minute. Then, turn away and write down as many as you can from memory:

Apricot, ladder, storm, headphones, spark-plug, sneaker, anchor, coin, library, twenty-seven, lyrics, nail, telescope, onion.

How’d you do? I could only recall nine of them (even though I was the one who made up the darn list just now), and in fact, I had to work hard to recall the eighth and ninth. By the way, IQ has nothing to do with this number. Whether you’re closer to Mensa or Densa, your short-term recall factor will still be 7 +/- 2. (See Wikipedia and George Miller’s 1956 paper that first noted the phenomenon is at www.musanim.com/miller1956/.)

As the Wikipedia article points out, Ed Yourdon first commented on how this relates to computer science back in 1979. He described what we would today refer to as the long-method smell (see www.soberit.hut.fi/mmantyla/BadCodeSmellsTaxonomy.htm), citing the magic number 7 as why it’s bad to tax the short-term memory of someone trying to understand a piece of code.

So, how often does your web framework require you to keep track of more than seven things at once? Take, for example, the simple task of creating a data-entry page. How many different files need to be created or modified to accomplish this? One for the HTML template, one for the page logic, multiple files for each model object (interface, impl, and ORM mapping), the DAO (interface and impl), the config file with the URL construction rules, the config file with the user security rules, the config file that lists all of the pages on the site, the interface file with constants for all those page names? — That’s eleven and counting. Sound familiar? This amount of complexity often leads to things falling through the cracks, and is usually reflected in a high number of bug reports.

From what I have seen, Ruby on Rails has made this particular task as simple as it can be, and that accounts for a great deal of RoR’s appeal, I’m sure. Even .Net has this down cold. In the case of RoR, it’s an innate feature of the framework. In the case of .Net, it’s simplified by the tools. I’m still waiting for a Java-based framework/environment that “gets it” in this regard.