Looking Beyond POS Design Heuristics

On more than one occasion, I've been asked about the design principles (heuristics) that I use to create a great design. That question is harder to answer than it might seem. There are certainly some good lists of usability principles available, but it's important to remember that while heuristics are good principles to follow, there are always times when (a) specific rules should be broken, and (b) contradictions between rules will arise. The trick is being able to weigh conflicting principles and apply each to the appropriate degree.

In the end, it's a matter of balancing the business requirements and user needs in a way that produces optimal results. And in the real world, I find that this can never be achieved through heuristics alone. For example, on the Case Studies page, I describe the Subway, Wendy's, and Starbucks projects. All of these projects used similar processes and solid heuristics, but each design came out very, very different because of differences in the business goals and requirements, the users' needs and background, the environment in which they work, the technology being used, and a whole host of other differences.

You can never create a great design in a vacuum. For each of the clients mentioned above, I traveled around to a lot of different types of stores in multiple countries to get a feel for how the users' worked, how the systems would be used, how customers ordered, etc. All this information—along with sales and other data provided by the company—was invaluable in creating a highly usable solution.

Here's another example: One POS heuristic I've come across is "Support [Left/Right] Handedness". This is fine as a heuristic, but in visiting Subway stores, we discovered that in that context, the location of the register actually plays a greater role in the hand employees prefer. In other words, registers that were squished against a wall on the right side tended to produce left-handed users, even when the users were right-handed for every other task. This had implications for the way we allowed the UI to be flip-flopped...and who had control of it. There are many, many examples like that, but we never could have achieved the tremendous outcomes that the user interfaces have produced by following heuristics alone.

One final point: Many times heuristics are incomplete without more information as to how to apply them. Consider the heuristic "Support Conversational Ordering". There's much more to this guideline than just providing flexibility in order entry. For instance, one of the many things you have to consider is that not all paths should be presented as equally probable. We analyzed the way Starbucks' customers ordered in various locations across the United States and United Kingdom. Then, we optimized the system for the most commonly spoken patterns. If we had allowed all paths to have the same "volume", we would have sacrificed usability in other areas, since the design would have appeared more cluttered.

Starbucks' new POS system now supports almost all possible order patterns, but the most probable paths are presented at a higher "volume" than those that are less probable. The moral of this tip is this: If you have a chance to visit the environments in which your POS will be used, analyze customer/employee interactions, etc. ...you should take it. Contextual observations and analysis are invaluable in correctly applying heuristics to a given situation.

NOTE: This tip was adapted from a posting I originally made on StackOverflow.com