Christmas is a good time for sitting around a fire and telling stories. Practice your storytelling this Christmas, and hone your interaction design skills for 2009.

People love stories. But beyond that, stories are fundamental to the way we think as human beings. Salesmen tell persuasive stories about successful installations and satisfied customers. Social workers pass on complex case histories as stories. Just about every culture in the world passes on valuable knowledge to the next generation in the form of stories.

When properly told, stories incorporate all the ingredients people need to think and learn: situation, actors, events, challenges, consequences... They help us gain a little of the benefit of direct experience, with much less of the pain.

So it makes sense that interaction designers need to be great story tellers. I've picked three kinds of storytelling used in interaction design...

• Scenarios
• Specification
• Rationale

Scenarios: Invent a story

Because we're not fundamentally good at imagining futures or situations different to the one we are in, we have to consciously and explicitly create stories to make sure we do things right. Interaction designers create personas (the characters in the stories), describe the context of use (situation and back story) and the personas' goals.

Then we create scenarios. We try to tell a compelling and realistic story of how our personas will reach a happy ending by using the product. Because we're all good at listening to stories, the team can spot the good ones, the implausible ones and the radical-amazing-breakthrough ones quite quickly.

Specification: Many stories

A specification - however sketchy or detailed - is a story. Actually it's many stories, captured simultaneously. What will happen if the user goes here or there? A good specification has a lot in common with a Choose You Own Adventure story. (Did somebody say adventure? Now there's some classic interaction.)

The trick for a good interaction designer, though, is to make sure that the story of your product has no dead ends. So the best specs spend plenty of effort on handling error situations, as well as just the positive story.

Rationale: Meta-story

The importance of rationale is often underestimated. Rationale is the story of how and why a design decision has been made. "We're doing it like this because..." When your storytelling has led you to a non-obvious (but demonstrably right) conclusion you don't want your team and your stakeholders re-creating all the failed stories you've already told all over again. It takes too long.

Rationale also demonstrates how much effort has been put into reaching a conclusion, so that the team doesn't forget how far they've come.

Pictures are not stories

A picture, in this context, doesn't tell a story so much as beg for one. A beautifully drawn image of an interface, frozen in time, might look persuasive - and it might hint at past and future interaction. But it doesn't answer many of the important questions: how do your users reach this point? Where do they want to go next? Will they know what button to choose? What will happen if they click that button? A picture on its own is open to misinterpretation by everyone who looks at it, from developer to CEO.

When you surround it with other pictures and information about the sequence they link in, then a story unfolds. And that's what interaction design is all about.

Mobile devices are the primary experience of personal computing for most people in emerging markets. Accessing content at prices these users can afford is all but impossible. But using sideloading and sneakernet, content can spread for free.

I was lucky enough to watch a great talk by Gary Marsden at the recent SA UX meeting in Cape Town. He talked about many interesting things, but this one captured my imagination the most.

In developing markets, mobile devices have much greater market penetration the personal computers. In South Africa, for example, around 77% of the population have mobiles but only 12% get online with PCs. So for hundreds of millions worldwide, the main, everyday experience of digital technology is probably a phone. When a phone is one of the few pieces of technology you've got, it's amazing what you will use it for. In emerging markets, mobile phones are becoming a primary mechanism for reading text, storing photo albums, watching video and listening to music.

Nokia has recently announced their $50 2323 phone, along with a suite of carefully targetted custom content to address this developing market demand.

But nearer the "bottom of the pyramid" the the cost of mobile data services is too much for most people to afford more than a trickle of bytes. Typical data consumption for a young South African might cost them around R7 per week, which is around 50 pence. Downloading MP3s or ebooks isn't realistic. So instead, some content is percolating across the community using bluetooth sideloading and sneakernet.

Sideloading sneakernet

Sideloading is a newish term, still ill-defined. But one meaning is that people can share content from one mobile device to the next, rather than downloading it from network servers.

Sneakernets are a venerable concept, still used by even the largest companies when the cost of electronic data transfer is too high. It just means that you carry data from A to B on a storage medium, instead of sending it over a wire. Google, for example, used blocks of disks to transfer 120 terabyte files.

If you put the two together you can transfer data to mobile devices for free, across any distance. Basically, one person sends a piece of content to another using bluetooth. The recepient can share their copy with more friends, and from them it can go on to more. The potential rate of distribution grows exponentially.

Riding the sneakernet

With only 6.6 degrees of separation between everyone on the planet, it's not hard to see that this could let content percolate quite fast. But our daily face to face contact is with far fewer people than our total network, so content will percolate more slowly, really.

Targetting connectors will help. The Tipping Point tells us that a few people in the world are connectors - they know a lot of people. To get a message out over a sneakernet, it would make sense to ensure it gets to the connectors.

In reality, it may be that most content won't hop quickly or reliably enough from user to user for many applications. So providing physical severs in public spaces to allow bluetooth content downloads looks like a more controlled option.

To do just that, Gary Marsden's team at the University of Cape Town, along with Microsoft Research have invented Big Board. It's a digital message board that allows people with ordinary, bluetooth-enabled phones to download text, images, audio and video for free. Most important, it requires no extra software on the handset at all - most phones can already receive mutimedia messages via bluetooth.

What content is worth distributing? For big board, community and local content make sense. Big board can also allow content to be uploaded to it, making it true, digital message board. Education and entertainment also fit well, and are good sneakernet fuel too. I've heard plans for using soap opera mobisodes to provide health education and AIDS awareness messages...

Further reading

• One Laptop per child: A formal sneakernet proposal for the OLPC initiative
• Wired: The real action in music sharing isn't online. It's on foot.