# RDFa and Digital Cities

## Some predictions I have heard

"We will never have LCD screens - they will need too many connectors"

"Vector graphics are the future; raster graphics need too much memory"

"Full audio on computers will need too much bandwidth"

"Digital photography will never replace film"

"Moore's Law hasn't got much longer to go" (1977, 1985, 1995, 2005)

## Moore's Law

We all know this one. But often people don't understand its true effects.

Take a piece of paper, divide it in two, and write this year's date in one half:

## Paper

2008

Now divide the other half in two vertically, and write the date 18 months ago in one half:

## Paper

2008
2006

Now divide the remaining space in half, and write the date 18 months earlier (or in other words 3 years ago) in one half:

## Paper

2008
2006
2005

Repeat until your pen is thicker than the space you have to divide in two:

## Paper

2008
2006
2005
2003
2002
2000
1999
1997
96
94
93
91
90
88

This demonstrates that your current computer is more powerful than all other computers you have had put together (and the original Macintosh (1984) had tiny amounts of computing power available.)

## The Cray

In the 1980's the most powerful machines were Crays

## Crays

And people used to say "One day we will all have a Cray on our desks!"

## And so tell us Steven, Do we all have a Cray on our desks?

Sure: in fact current workstations are about 120 Craysworth.

Even my previous mobile phone was 35 Craysworth...

## Nielsen's Law

What is less well-known is that bandwidth is also growing exponentially at constant cost, but the doubling time is 1 year!

(Actually 10½ months according recently to an executive of one of the larger suppliers)

Put another way, in 7 years we could have 1 Gigabit connections to the home.

## Why I am here

CHI Conference, I normally go, but by chance not this year.

KPN manager: I send my engineers to all the telecom conferences, but CHI is the one where they come back with the answers from.

Great kenot on heads-up displays in jet fighters in 1995 (?)

Thanks to the ash plume: everyone from Europe is still there.

## CHI 97

I was the conference co-chair of CHI 97

## AR at CHI 97

(Taken with the first commercial non-professional digital camera, released the year before. Only QVGA, and terrible photographic quality. Good to see how far we've come)

## AR

(Lookpaintings from Steve Mann's website)

## interactions

I was editor-in-chief of this for the best part of a decade. This issue from 1999 (three years before the first commercial camera-phone) was my favourite: a study on how people would use mobile phones if they had cameras in them.

## Camera phones

The backpack contains all the electronics that would be in the real mobile phone.

## AR now

Satnav is the most common form of AV at the moment.

## AR now

If you are lucky, it even has live data.

## AR now

Emerging forms of AR seem to use mobile phones - leverage of the fact that people already have them. This is ARound.

This is Layar

## AR now

AR can also be useful for assistive purposes.

## Digital Cities

Data, data, data: You've got your reality, where are the augmentations going to come from?

And you don't want to publish your data multiple times (like RSS)

## Internet Guide to Amsterdam

Since 1994-5 (written in 1993)

## Amsterdam Guide

Contains loads of information that is useful when in Amsterdam. If it were machine readable, an aggregator could use it to assemble information about Amsterdam for other uses.

## RDFa

Like CSS, which adds a layer of markup to influence presentation, RDFa adds a small layer of markup that adds semantics to documents.

Now a browser can know more about the page you are looking at.

If you are looking at a page about an event, the browser could offer to

• Show a map of where it is
• Find hotels
• Find flights
• Tell you about the city it is in

etc.

RDFa can also help search engines, and even allow the creation of new sorts of 'aggregators'.

## RDF

RDF is a very simple framework for representing data.

Much more flexible than other storage forms.

One of the reasons this is good comes from Metcalfe's Law

## Metcalfe's Law

Metcalfe proposes that the value of a network is proportional to the square of the number of nodes.

v(n)=n2

Simple maths shows that if you split a network into two, it halves the total value:

(n/2)2 + (n/2)2 = n2/4 + n2/4 = n2/2

This is why it is good that there is only one email network, and bad that there are so many Instant Messenger networks. It is why it is good that there is only one World Wide Web. It is why you don't want unlinked silos of data.

## RDF Data

Each entry has three pieces of information:

• What you are talking about
• A property
• The value of that property

E.g.: [Roses-Cantina] [Cuisine] ["Mexican"]

The first two of these are always URIs. The third is a URI or literal.

## RDF representation

RDF can be represented in many ways

`Roses-cantina {Cuisine: "Mexican"}`

We don't care; it's the data that matters.

## Ontologies

Are collections of properties over a subject area (for instance restaurants, recipes, reviews, events).

There is an emerging set of standard ontologies.

There are ways of expressing the relationships between different ontologies.

Properties in different collections are uniquely identified:

```committee:chair
furniture:chair```

## RDFa

Is just another way of representing RDF-based data.

The 'a' stands for attributes, since RDFa uses attributes to signal data.

```<p typeof="service:restaurant">
<strong property="service:name">Rose's Cantina</strong>

href="tel:+31206259797">6259797</a>```

(The ontologies used here are made up, for the sake of simplicity)

## RDFa overriding

```<span property="restaurant:cuisine"
content="cookery:mexican">Mexican</span>```

Language independent

Allows cuisines to have properties as well.

```<p about="cookery:mexican">As the name suggests,
Mexican cuisine originates from
<span property="ont:origin">Mexico</a>
</p>```

## RDFa usage

Beginning to be widely used: BBC, Governments, Google, Yahoo, Tesco, Best Buy:

"GoodRelations + RDFa improved the rank of the respective pages in Google tremendously …

30% (!) increase in traffic …

Yahoo observes a 15% increase in the Click-through-Rate …”

## Reality augmentations

You are three minutes from there

## Reality augmentations

You are three minutes from there. Astrid likes it too.

## Conclusions

AR needs data to work with.