As we all know Interactive Digital TV, or iDTV, is growing and at a pace that hasn't been seen since the uptake of Internet access through computers by the general public in the early nineties. The BBC, BSkyB and the consortium of ITV and cable TV companies are the main proponents in the UK. Each is now offering a range of services on the back of their digital broadcasts. The BBC for example has had interactive services for their major sporting events such as the World Cup, the Open and Wimbledon. These services are supposed to allow users to choose the match they wish to see rather than the one that the BBC decides to show on BBC2, or view a wealth of stats and opinion. The content providers on BskyB's SkyActive Platform offer a more diverse range. On this platform there is interactive shopping with high street stores, betting, and information as well as interactive programming such as Premiership football. The real question is not whether people will use the services but whether they will be able to?

There are a large number of differences between the Internet on a computer and iDTV services and these have significant impact on good interaction design. The first is that so far all services on iDTV are part of a walled garden meaning that the user can only interact with sites and services that the operator has allowed. This also gives the service operator an element of control over the design of the sites. Unfortunately so far they have seemingly failed to implement good standard templates that incorporate high standards of usability. There are many complications that may form part of the answer to this. Operating systems are not standard. Each provider has a different system;0 some even have more than one on their own platform and different rules for design. This means that content providers have to build new and custom solutions for each outlet they wish to have a presence on. Secondly content providers, and often operators, are still tasking web services teams with building these new interactive services for a totally new and very different platform. A lack of experience and understanding of the technology is leading inherently to poor customer experiences as the technology fails to support user goals.

Some of the fundamental differences between standard web interfaces and iDTV interfaces are very simple. The first of these is the screen size and resolution. These limit the amount of usable real estate on an iDTV platform to a vastly smaller area. It also means that those users on a 4:3 portable can be just as easily catered for as those with a 42-inch plasma screen. The web user on the other hand may have many different versions of browser, screen size and resolution and this is before elements such as operating systems and assistive technology concerns are addressed. The television interface being much more simple however is more a case of one size fits all. As the resolution is always the same, as it is dependant on the number of lines that are broadcast, this a standard and cannot easily be altered. The benefit of this for a designer is obvious.

Secondly, the most common thing a user will do on the web, after pressing the "back" button, is to scroll the page they are seeing. This is not easily possible on an iDTV screen as there is no simple method through which to do it. This leads on to the next fundamental point. Every computer that has been sold to the general public in the recent past has had a direct manipulation device (the mouse) interaction style. This is not possible on TV and the user, and the designer are limited to what can be achieved using a remote control that has to jump step by step from one interaction point to another in a set order. The implications of this are that instead of the many links you might see on the Yahoo homepage (www.yahoo.com) each iDTV page can only have a limited amount of links on it before the user cannot be bothered to step between them all in sequence to find the one they want. This is another substantial impediment to the theory of open Internet access through your TV.

Yet more ingredients are thrown into the mix once you start to consider the conditions under which the services will be used. Almost all services are currently directed at the domestic user. In the vast majority of cases it is likely that the TV with interactive capabilities is the primary TV in any given household. For this if no other reason there will be debate in many households over what is watched at any given time? If the TV is being used to send email, browse an online supermarket for the groceries or look up what is on at the cinema in the users area, then this can only lead to more disagreement. As the TV becomes a two-way interaction device like the personal computer it becomes less an entertainment medium in its original form. This has ramifications for interface design. Some of these lessons are already being learnt as the BBC and Sky let the user watch their original program in a smaller screen field whilst they interact for certain tasks, whilst the sound is carried in the background throughout the process.

The final and by no means least important element is that from user evaluation of several services it has been found that the user has little if any concept that they are online and accessing the Internet through their phone line for many of the transactions or processes they are undertaking. Even if they do the sites make little reference to when they are connected and as a result when they are incurring telephone charges! This makes users nervous and in some cases angry that they have in some way been duped into spending money they either didn't want to or more than they intended.

The conclusion is that as this technology expands into the market place it needs to concentrate on the level and quality of service it is really providing to its users and shareholders. It is all very well to tell the board that the new service has launched and is performing well, but how well, and how much better could it be if it had been better designed with the user in mind? These are the questions managers are now asking about their websites, why should iDTV services be any different?

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