In the book, Norman rails against the usability flaws which seek to undermine our comfort and sanity. Everything from lightswitches which never seem to have a consistent state, to to alarm clocks with impossible to figure out controls. It really is a must read for anyone who cares about usability - on computers or in the real world.

I travel a lot for business - and occasionally for pleasure - so I get to experience some of the maddening issues which Norman describes fairly regularly. Nowhere is this more apparent than hotel rooms.

Hotels From Hell

I'm not talking cockroach infested flea pits with constant building works and mouldy bathrooms - although I've seen a fair few of those - but irritations which confuse, confound and exasperate a weary traveller. TVs with seemingly no volume control. Light switches which operate lamps on the other side of the room. Door locks which require an engineering degree to operate. Thermostats which either leave the room freezing or baking. All pretty trivial, yes - but of immense frustration to a jet-lagged guest who just wants to turn the lights off and sleep in a warm room.

Bathroom Blunders

The area which seems to cause me the most confusion is the bathroom. We've all experienced the shock of using someone else's shower and having them patiently explain what the trick is of turning it on - or getting it to spurt out hot water... but not too hot. Hotels, sadly, rarely come with a guide to using their facilities.

I want to point out an "interesting" usability flaw I noticed on a recent trip to Paris.

Hot Cold Confusion

What would you expect this tap to do?

The blue / cold symbol is over the spigot - surely that means activating the tap will pour cold water?

However, our experience indicates that turning a tap to the left brings forth hot water - that's the convention in my country. Is it the same in France?

There are no arrows to indicate how turning the tap will affect temperature.

We could experiment - but most people don't want to waste time with that. They just want a clear indication of what a piece of equipment will do.

So, we have an impasse. The law of proximity would indicate that two things next to one and other have a relationship. The cold symbol is next to the tap - therefore the tap will run cold.

The law of experience tells us that turning a tap to the left gives hot water.

There is no way to reason this out. We have to go through an annoying - and possibly painful - experiment to see how this mundane piece of equipment works.

Lessons

The lessons for computer and real-world usability should be clear. Don't make the user think. Don't mess with their expectations. Don't overload conventional actions with your specific action. Try to see every aspect of your project as though you were a brand new user who is unskilled in the ways of your project and of your culture.

Above all, remember that some of your users are likely to be jet-lagged and just want the simplest, easiest way to perform an action.

You can buy The Design of Everyday Things from all good bookshops.

A few years ago, Miss Geeky introduced me to Space Invader spotting.

Dotted around the cities of the world are mosaics of Space Invaders. Placed there by a mysterious artist - seemingly at random.

Before I went to Paris, I had no idea that there were any Space Invaders lurking on street corners. I've since realised that it's possible to get fairly detailed maps of where the invaders are. Or rather, where they are supposed to be - they have a habit of moving. Or, more likely, being stolen!

For me, running around the city specifically looking for the little blighters ruins the sheer joy of finding them by chance. We spotted nine in total - one of which was on the banks of the Seine, but our boat moved too quickly for me to capture it.

Here are photos of the ones that I found. Annoyingly, my Nexus One didn't geo-tag the images - hopefully the street signs should give you a clue as to where they can be found.

So, next time you're in a big city - keep watching the skies!

Like a good many of you, I was completely unaware of Íñigo Melchor de Velasco, the 7th Duke of Frías. But then, how many of us know the person we are destined to become?

Looking at the picture, staring into those familiar eyes, I felt like I was looking into a mirror. A mirror which showed the future. I wanted to snap a picture but I had run out of film - these were the days before digital cameras. By the time I had found a shop selling the right film for my Kodak, the museum had closed and I was left wondering if I would ever find the painting again.

Last weekend, I took another step on the path which will lead me to time-travel. I now have evidence that I will become a master of time. I shall bend the fourth dimension to my will!

Hanging in an almost forgotten corner, behind a wall, is the most extra-ordinary painting. It is that of a minor 17th century Spanish noble. Quite unremarkable except for one unique feature. It is a painting of me.

Staring at it was like looking in a mirror.

At some point in the future, I shall travel back to the past...

Here's a comparison with slightly more detail.

You need to imagine my face tilted down slightly - and my hair over both shoulders. There can be no doubt that this is a photo of me.

How I end up governing the Spanish Netherlands is a mystery to me. I'm searching the painting for clues I would have expected to have left myself - but I can find none.

What confuses me is the paradox of time-travel choice. Do I go back to the 1600s because I've seen this painting? If so - why did I choose to go originally? All very wibbly-wobbly timey-wimey... stuff...

There are some great examples of how to do 2D code marketing - and how not to do it. I'd like to run you through a few of examples I found. I've enhanced the photos to make the codes a bit more obvious - that should make scanning them easier.

QR

QR Codes seem really popular in Paris.

The free tourist map which our hotel gave to us had three of them! Interestingly, they all use the 2tag aggregator rather than using their own URLs.

What I found most impressive was that all three codes lead to mobile friendly sites! Try them for yourself.

This movie poster gets in on the act as well. Sadly, not a mobile friendly site - but it gives good information.

Even the graffiti uses them! These were stuck on lamp posts throughout the city. The codes don't cope wonderfully when deformed around a cylinder - but are scannable with a little patience. Placing two codes close to each other as seen on the right of the image isn't a great idea - scanners tend to get a little confused when they see multiple scanning guides (the large black squares in the corners).

But QR codes are by no means the only technology on offer...

DataMatrix

There's a production of "My Fair Lady" on in Paris at the moment. Tucked away in the corner of the poster is, to my eye, a rather ugly looking DataMatrix code. While the pink background shouldn't provide too much of a scanning challenge for modern phones, it's usually best to keep things black and white. Especially given the complexity of this code, caused by the long URL. There's nothing wrong with using a URL shortner. The site isn't mobile friendly - even worse, it relies heavily on Adobe's Flash. The one saving grace is that it's a fully qualified link - unlike what you're about to see.

Flashcode

It's no secret that I think Flashcode is an abomination. Essentially it's a datamatrix code - but rather than give you a URL, it gives you a number. Your scanning application then looks the number up in a central database to find the content. It should be fairly obvious what the pitfalls of this method are. It relies on a single point of failure and if you don't have the right scanning software which hooks up to the correct proprietary database - you're out of luck. When I scanned these codes with my scanner of choice - ZXing - all I saw was a string of numbers. I have found only one Flashcode reader for Android - "mobiletag".

I really wanted to see this sci-fi exhibition - but I couldn't decode the 2D code into anything useful.

Similarly, this poster gives most scanners no information.

I later found that it points to http://mtag2d.com/euro/ - a perfectly nice mobile site. That URL is short enough to generate a really tiny QR code.

I get the attraction of Flashcode. It's a great way to make money - selling scanners to customers and selling access to the database to advertisers. The codes are generally smaller which makes them easier to scan and more aesthetically pleasing.

In my opinion, they're a dead end. Unless Flashcode makers are going to ensure that every possible device on the market will have a reader which is compatible, they're never going to achieve the dominance of an open standard like QR.

The reliance on a central database has two fundamental flaws.

1. What happens when the database goes down? Either if the company goes bust or suffers a DDoS attack?
2. The user may not have data connectivity. Because I was roaming, I had data switched off. With the QR codes, I could save the URLs until I had a WiFi connection.

But, the worst is yet to come...

Image Recognition

On nearly every bus shelter I saw these stickers.

In mid October, JCDecaux launched "U snap". The concept is quite simple - snap a picture of an advert and receive information about it.

Unfortunately, it is fundamentally flawed.

• It is for iPhone only. France, like the rest of Europe, has an iPhone penetration rate of around 5%. Why would you ignore 95% of potential customers?
• Even if they did launch their own proprietary scanner for every other phone platform, they'd have to change the stickers on every shelter.
• There's no way of knowing which posters have information on them. I hope JCDecaux has data for every single advert in their inventory.
• It requires an immediate data connection. Paris has really good 3G coverage - but not everyone wants to pay to receive information about your data. Hopefully the app has an "offline" mode which will allow you to queue queries until you're in cheap data coverage (WiFi or not roaming).
• Because the posters on bus shelters are behind glass or plastic, it becomes very hard to snap a clear picture. I wonder what this does for accuracy?
• 

I think image recognition is amazing technology. Companies like Cortexica blow me away with their innovation and technical prowess. But for sending a user to an information page via a URL, displaying a phone number or email address, image recognition is simply overkill.

I'll grant you, it means you don't need to "sully" your creative with a set of black and white squares - but you do need to put instructions next to every poster so people know what to do!

Conclusions

The 2D barcode scene in Paris is extraordinarily vibrant. While the majority of posters still had no mobile accessible link, there were enough to catch my eye over a weekend break.

Based on what I saw, QR is definitely the favourite - with the appalling flashcode a close second. The image recognition prompts from JCDecaux are ubiquitous - stuck on literally every bus stop I passed - but unless they expand their app to cover more platforms, they're doomed.

It's great to see a city decorated with physical hyperlinks. I really hope London catches up soon.