Ash at CIID

Ashwin Rajan's blog while at the Copenhagen Institute of Interaction Design.

The Flexibility-Usability Tradeoff: an Illustration

with 2 comments

I recently came upon a delighful little product on my flatmates’ shelf that illustrates the ‘Flexibility-Usability Tradeoff’ principle very well. The Bosch IXO is a great example to show that when you choose flexibility, you risk usability.

In this context, what is meant by usability may be far more apparent than what ‘flexibility’ means. One way I understand flexibility (especially in product design) is the range of distinct or largely unrelated features on a product. My Timex Ironman Triathlon digital wristwatch is a highly flexible device in terms of ‘operable’ features – it shows time, can be used as a chronograph (lap/split), has a 30-lap memory recall, Indiglo, countdown timer, alarms, two time zones, built-in setting reminders, and more. It has one screen, and a total of five buttons labeled ‘Mode’, ‘Start/Recall’, ‘Indiglo’, Stop/Reset’ and ‘Start Split’. Figuring out and using all of these with effortlessness, as you can guess, mandates a detailed manual and considerable practice.

The TIMEX Ironman Triathlon 30 Lap - requires the patience only a professional can spare.

The TIMEX Ironman Triathlon 30 Lap - requires the patience only a professional can spare.

The Bosch IXO, on the other hand, does one thing and one thing only, and boy does it do it well! Its a cordless electric screwdriver, period. The few controls it does provide broaden the feature set, but they represent a very different kind of flexibility from the Timex altogether – they are only features that enhance the core function of the product (see captions of images below).

Purpose meet elegance. The set of screw heads stack on the dock which also serves as the charger of the device.

Purpose meet elegance. The set of screw heads stack on the dock which also serves as the charger of the device.

A simple two-way pin that toggels from side to side can be pushed to set the working of forward or backward (screw or unscrew) motion.

A simple two-way pin that toggels from side to side can be pushed to set the working of forward or backward (screw or unscrew) motion.The big red button runs the device.

A set of three LEDs of one color (green) are grouped on the top face of the device. They provide feedback when the machine is running (forward/back arrows) or when the machine is charging (middle).

A set of three green LEDs (no other color states) are grouped on the top face of the device. They provide feedback when the machine is running (forward/back represented by arrows) or when the machine is charging (middle).

And finally, a light is directed at the source of screwing when the machine is run.

And finally, a light is directed at the source of working when the machine is run!

That’s really all there is to it. So simple to comprehend, such a delight to use.

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Written by Ashwin Rajan

January 11, 2009 at 9:01 pm

2 Responses

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  1. Great Study…Like to read more like this…

    – Ramesh,CUA,Chennai

    Ramesh.K

    November 4, 2009 at 8:24 am


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