Archive for August, 2009

Long number Entry and Equal Opportunity

Sunday, August 30th, 2009

I recently worked on a security application where the employee used a swipe card to identify themselves at certain locations. The event of identifying themselves was transmitted to a server, which had a database which contained the mapping from the serial number of the swipe card to the name of the employee.

All o f the employee records existed in a database. As we added cards to the system, the long and unwieldy swipe card number had to be entered manually into the employee’s record to create the mapping. As with any long-number entry, there is a risk that the number was entered incorrectly. Checksums within the serial number detected some faults but it was still not very satisfactory. And if the mistake was not discovered immediately, it led to hassle for the employee and supervisor the first time the card was used.

As we thought through this challenge, one option would have been to add a card reader to the server, or the PC accessing the server, and allow a card to be swiped instead of typing in the number. This added a number of unwelcome challenges. This reader would be different from the already installed readers since the communications link was different. The server was updated via the web, so you could not be sure where the user would be located, and restricting them to one location or PC would be troublesome.

Many solutions look so obvious after the fact and this was one of those cases. We eventually realized that the scenario where a card is unrecognised also provided the ideal opportunity to enter the correct user name.

So when the card is not recognised, instead of simply rejecting the user, the supervisor has the opportunity of picking a name from a list of employees, and the mapping from card number to employee is then created. This solution requires no extra hardware. The supervisor no longer has to type in long error prone numbers. The card can be swiped at any location, so when a new employee receives his card he simply goes to his nearest access point, and over the phone, tells the supervisor that he is about to swipe for the first time. The swipe is unrecognised, and the supervisor sees the new serial number, and its location, and links it to the appropriate employee.

This is a case of applying a principle called equal opportunity. It means that something that was delivered as output to the user can be turned around and used as input. This means that the user never has to enter the original data, since they received that data as output. Another example would be receiving a call on your cell phone from an unrecognised number, and being allowed to add it as a contact without having to type in the number all over again.

My online tutorial on equal opportunity provides a number of other examples of this useful technique:

Measurement Changes Everything

Saturday, August 8th, 2009

Introducing an electronic or computerized system to a human activity often opens up opportunities to measure aspects of the activity that could previously not be monitored in any cost effective way. This column strays a little from pure usability issues, but the nature of the measurements you take is partly a feature-set decision, but it also dramatically changes the nature of the relationship between your device and the people using it. In this column we will first look at systems as diverse as call centers, pulse oximeters, and running aids that tell athletes their pace and distance.

Consider a call center routing phone calls to a band of support or sales staff. Once the call routing is computerized, it is possible to measure the exact duration of each call, the time before a call is picked up and the amount of time between each call. These numbers can be used to measure productivity of employees. Once that productivity can be measured then many steps can be taken to increase it, such as linking pay with the percentage of a person’s time they spend on the phone. A case can be made that such measurements make the work place more pressurized, less pleasant, and might occasionally cause the most talented employees to seek employment elsewhere. That is a discussion on quasi-ethical issues that I am not interested in addressing here – the main point is that the measurements, which are a side effect of the call routing system can have a profound effect on the control of the system.

In other cases the measurement is not an incidental by-product, but the core purpose of the system. In medical devices, many innovations have been in the area of providing real time measurements of attributes that had previously been only occasionally measureable. Pulse oximeters give real time feedback on blood oxygenation levels. Previously a blood test was required, and this limited the number of samples that could be taken, and by the time the sample data came back from the lab, the patient condition could have changed. Modern respiratory therapists can make minor adjustments to a patient’s lung ventilator or to their medication, and then observe second-by-second the impact of the adjustment. It even opens up the possibility that the control loop could be closed by automatically adjusting lung ventilator parameters’ in response to changes in blood oxygenation levels. This has been implemented in experimental cases, but is not a mainstream solution.

At one point in my career I thought that the cutting edge of medical device development was working on therapeutic devices that delivered treatment to the patient, but I now realize that measurement can have just as big an impact on patient outcome. If doctor’s decisions are based on guesswork rather than raw data, then they are going to make less precise diagnosis.

Another area that has been revolutionized by measurement is running. In the past few years, consumer devices which tell you how far and how fast you run have come to market and proved extremely popular. Some are based on a foot sensor that measures how many paces you have taken, and others are based on GPS technology to measure the distance and route of the run. This is not just a replacement of a stopwatch – because the feedback is real time during the run, these devices can provide a motivating influence that is almost as good as having a running companion who is always a couple of seconds quicker than you.

One of the big advantages of using a gym (which I do not visit often enough, but that is another story), is that most activities are precisely measurable. If I am on the treadmill for 20 minutes, it can tell me precisely how far I ran and how fast. If I return to the gym tomorrow (well OK – next week), I can try to equal or better that run, which is a huge motivational factor. Even the gym activities that do not involve electronics allow me this precision of recording. The number of chin-ups or the weight that I bench press are numbers that are easy to record.

Road running always contains a vagueness that does not happen in the gym. Unless I run precisely the same route, I cannot compare times. Even with the same route, it is difficult to know how I am performing while I am on the run. I want real-time feedback, not just a result at the end – too late to motivate me to do a final sprint. A system that measures my pace as I run, and tells me whether I am faster or slower than my target speed revolutionizes road running. I can now pick any road and just go.

It is interesting to note a couple of the differences between the two main technologies. If you use a shoe sensor then it requires calibration to match your typical stride length. A GPS based system avoids this issue and also offers the advantage that it can record the actual route and later superimpose it on a map when the route data is downloaded to your PC.

The Nike+ system is a collaboration between Nike and Apple. At first glance I was surprised that Apple did not opt for the GPS solution. They are the kings of simplicity, and would have wanted to avoid the calibration step. While I am not sure what the rational was, a case could have been made that GPS raised other complexity issues – battery life means that you have to remember to charge the device between runs – at least that is true for the Garmin wrist-watch based devices. While GPS adds lots of extra information because it knows the route, it could be argues that most of that information is superfluous – the runner just wants to know how far and how fast. So maybe their rational was to choose to measure the things that help motivate the runner, but avoid flooding them with so much data that only the statistics junkie is interested.

There is a good article on the motivational effect of the Nike+ at

I also wondered about the effect of a shoe sensor that might have accuracy issues as terrain, weather and fitness levels varied. It then struck me that the accuracy would be rarely tested and so a few percent of an error would go unnoticed by the runner. If you are trying to break your personal best for five miles and your monitoring device tells you that you have improved by ten seconds, when in fact you have improved by 5 seconds, then you will not realize this. The important thing is that the motivational effect of seeing an improvement is still there. Accuracy only matters if you are comparing the results to some reference, and these devices are not used to record world records, so no one will really care.

Adding measurement and recording to a device can also introduce a bond between the device and owner, which has advantages in terms of marketing – the owner feels the device is like a pet dog that actually knows the owner. It has a disadvantage for the owner that it can become impossible to share the device. If I borrow my wife’s Garmin 405 to go for a run, it cannot tell the difference between my run and the ones my wife has done, and so her weekly mileage stats will be messed up. They could have incorporated a multiple-user feature, but that adds complexity, and I guess the marketing people figured it might also reduce sales. They would obviously prefer that each runner bought their own rather than have one device shared between two or more runners.

Have a look at your own designs and see if there are opportunities for game-changing measurements that will alter the way your system motivates the user.