Maintaining Consistency

Consistency is important because it helps users familiarise themselves with an application or site as quickly as possible. That means reduced training costs (both formal and informal), and, in the case of the online environment, a much greater probability of retaining customers and visitors.

'Be consistent' is a standard piece of advice for anyone designing applications, interfaces or e-business sites. At first glance it seems like obvious and unambiguous advice, but there is more to consistency than initially meets the eye. Consistency is important because it helps users familiarise themselves with an application or site as quickly as possible. That means reduced training costs (both formal and informal), and, in the case of the online environment, a much greater probability of retaining customers and visitors.

But what does consistency really mean? It is possible to identify three separate ways to approach the question of consistency, each of which is discussed below.

Consistency within an individual application.

Perhaps the most obvious and important requirement is to ensure that within the confines of an application or site, all interface elements remain consistent to the user. This goes beyond look and feel questions to include issues of language, system design and user feedback. It is essential that all these aspects of an interface remain consistent if the user is to avoid becoming confused and frustrated.

Consistency within a suite of applications or sites.

For a variety of reasons, applications or websites that may have little in the way of shared history can end-up as part of a 'suite' or package. When this happens, users will often expect 'consistency' from applications that have little in common either in terms of functionality provided or interface design. This represents a significant challenge to the organisation supplying these products. It is worth asking the following questions before embarking on a consistency program for application suites:

• Is a suite of tools appropriate, or should individual applications and sites remain targeted at their specific audiences and designed accordingly? When answering this question it is important to ask whether the target user group uses all the applications to be standardised. If they don't, you may end up compromising usability in individual applications for consistency benefits that no user group actually needs for. At www.channel4.co.uk, for example, different programming areas have individual sites that are designed for their target audience - and which are not necessarily consistent with the rest of the site.
• Do the benefits of consistency across applications outweigh the compromises that have to be made to each individual interface? Unfortunately this can be hard to quantify, especially as the benefits of intra-suite consistency tend to emerge over time, whereas changes to specific interfaces are more immediately noticeable and may elicit a negative reaction from existing users.

Despite these reservations, when users are likely to use several suite applications together, it is imperative to ensure that common elements that occur in all of them are represented and operated consistently. Failing to do this can result in serious efficiency and user satisfaction issues.

Consistency with the outside world.

In the modern business environment, companies are less and less likely to have the complete loyalty of their customers. Most application users are likely to experience a wide variety of applications, and particularly websites, during a working day. This means that, as much as possible, designers should attempt to utilise those elements that have become 'standards' within the industry. These standards can come from a variety of sources, including:

• Other products or services. To quote an obvious example, when building web sites it is conventional to place navigation on the left. Although that might not always be the most appropriate solution, users will begin to expect it at every site and be disturbed if it is moved.
• The interface conventions of the environment in which an application will run. If a user is familiar with the Windows environment, it might help to adopt certain 'conventions' that exist within the OS.
• The outside world beyond the desktop. It can often be helpful to use metaphors and concepts that users are already familiar with. The 'wastebasket' used by Apple (now an environmentally friendly 'recycle bin' in Windows) is an example of a real-world concept that enables IT interfaces to draw on existing mental models and thus shorten learning curves.