Consistency Management

Consistency is the best way to stimulate learning and create user comfort. It is also one of the hardest elements in interaction design. It would be relatively easy to make two solutions consistent with each other, but the reality is much more complicated than that. In fact, there are four types of consistency that have to be managed in parallel.

Intra-application consistency. From a device point of view, the first aspect of consistency is intra-application, which means that all user-related elements of an application should be internally consistent. Let's say that the application is a calendar. To be internally consistent, the steps for booking a meeting should follow the same logic as the steps for making a to-do list entry.

Interapplication consistency. The second aspect of consistency is that between applications. Interapplication consistency means that creating a note on a notepad should not be different from creating a note in the calendar.

Intrageneration consistency. The third aspect is intrageneration consistency within the user interfaces of the product range. At any given time a Nokia phone model in one market segment should resemble models in other segments to the extent that the style segmentation allows. Intrageneration consistency creates challenges for the scalability of solutions. Using the same graphic metaphor for similar things will signal interoperability to the user, so if both products carry an envelope icon adjacent to a messaging application, it is likely that they can communicate with each other. However, many mobile phone displays have so few pixels that solutions that would be applicable in larger resolutions simply do not work. For example, a postcard symbol was used for text messaging in the first two Nokia communicators, but not in the smaller phones-it just wasn't possible to design a postcard icon six pixels high.

Intergeneration consistency. The fourth type of consistency is intergenerational. The industry average for consumers upgrading their phones is 18 months. Since the typical phone model lifecycle in the industry is about 12 to 14 months, this means that if they replace their old phone with one belonging to the same category, they will be buying every second model. Suppose that the new phone behaves in a different way. The reason must always be a clear improvement that the user learns to appreciate. Change for change's sake generates negative consumer reactions. Obviously, intergeneration consistency may conflict with technology evolution, not to mention revolution.



Mobile Usability(c) How Nokia Changed the Face of the Mobile Phone
Mobile Usability: How Nokia Changed the Face of the Mobile Phone
ISBN: 0071385142
EAN: 2147483647
Year: 2005
Pages: 142

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