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The Semantic Web

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The word semantic stands for the meaning of.

The semantic of something is the meaning of something.

The Semantic Web = a Web with a meaning.

What is the Semantic Web?

The Semantic Web is a web that is able to describe things in a way that computers can understand.

The Beatles was a popular band from Liverpool.
John Lennon was a member of the Beatles.
"Hey Jude" was recorded by the Beatles.

Sentences like the ones above can be understood by people. But how can they be understood by computers?

Statements are built with syntax rules. The syntax of a language defines the rules for building the language statements. But how can syntax become semantic?

This is what the Semantic Web is all about. Describing things in a way that computers applications can understand it.

The Semantic Web is not about links between web pages.

The Semantic Web describes the relationships between things (like A is a part of B and Y is a member of Z) and the properties of things (like size, weight, age, and price)

"If HTML and the Web made all the online documents look like one huge book, RDF, schema, and inference languages will make all the data in the world look like one huge database"

Tim Berners-Lee, Weaving the Web, 1999

The Resource Description Framework

The RDF (Resource Description Framework) is a language for describing information and resources on the web.

Putting information into RDF files, makes it possible for computer programs ("web spiders") to search, discover, pick up, collect, analyze and process information from the web.

The Semantic Web uses RDF to describe web resources.

If you want to learn more about RDF, please read our RDF tutorial.

How can it be used?

If information about music, cars, tickets, etc. were stored in RDF files, intelligent web applications could collect information from many different sources, combine information, and present it to users in a meaningful way.

Information like this:

Car prices from different resellers
Information about medicines
Plane schedules
Spare parts for the industry
Information about books (price, pages, editor, year)
Dates of events
Computer updates

Can it be understood?

The Semantic Web is not a very fast growing technology.

One of the reasons for that is the learning curve. RDF was developed by people with academic background in logic and artificial intelligence. For traditional developers it is not very easy to understand.

One fast growing language for building semantic web applications is RSS. If you want to learn more about RSS, please read our RSS tutorial.

In the following pages of this tutorial we will concentrate on using RDF to discover the potentials of the semantic web.

Buying and selling used cars

Suppose a semantic web system was built to administer the selling and buying of used cars over the Internet.

The system would contain two main applications:

One for people who wanted to buy a car
One for people who wanted to put up a car for sale

Let's call the Internet applications for IBA (I Buy Application), and ISA (I Sell Application).

IBA - The I Buy Application

People who want to buy a car could use an IBA application much like this:

I Buy Application (IBA)

In a "real live" application you would be asked to identify yourself the first time you used it. Your ID would be stored in an RDF file. Your ID would identify you as a person with name, address, email, and ID number.

When you submitted the query, the application would return a list of cars for sale, and the list could be drilled down and sorted by year, price, location and availability. This information would be returned from a web spider continuously searching the web for RDF files.

ISA - The I Sell Application

People who want to sell a car could use an ISA application much like this:

I Sell Application (ISA)

When you submitted the form, the application would ask you for more information and store your ID and the information in an RDF file made available to the web.

The RDF file would contain information like:

Your ID: Name, address, email, ID number.
Your selling item: type, model, picture, price, description.

Behind the scenes

Behind the scenes, the "ISA" application creates an RDF file with a lot of RDF pointers.

It creates an RDF pointer to a file with information about you, an RDF pointer to information about Volvo and Volvo models, an RDF pointer to Volvo dealers and resellers, about parts, about prices, and much more.

An RDF pointer is a pointer (actually an URL) to information about things (like a knowledge database).

The beauty about this is that you don't have to describe yourself, or the car model. The RDF application will sort it out for you.

Will it ever work?

Chaos? Standards? What do we need? What are we waiting for?

A standard by W3C, by Microsoft, by Google?

RDF is data about data - or metadata. Often RDF files describe other RDF files. Will it ever be possible to link all these RDF files together and build a semantic web?

No one knows, but someone will try.

Will it work all by itself?

I don't think the semantic web will work all by itself. It will need some help to become a reality.

It is not very likely that you will be able to sell your car just by putting your RDF file on the Internet.

The "ISA" and "IBA" applications above will have to be developed by someone. Someone will have to build a search engine database for all the items, and someone will have to develop a standard for it.

It might be eBay, it might be Microsoft, it might be Google, or someone else. But someone will.

Soon we will see marketplaces based on RDF. And one day you will be able to collect information about almost everything on the web in a standardized RDF format.

It might not be free. You might have to pay for the information, or at least for selling your products.

Publishing information about things on the Internet will be much easier than before. Maybe the RSS language (see our RSS tutorial) will be the solution to some of the problems.

Semantic Web Agents

The semantic web will not be searchable in free text. To search (or access) the semantic web, we will need some software to help us.

To use the semantic web, we will need "Semantic Web Agents" or "Semantic Web Services". These "Agents" or "Services" will help us to find what we are looking for on the semantic web.

On the semantic web, we might want to look for information about:

The cheapest airline tickets
Styling that would fit my car
Books, DVDs, and CDs
Weather forecasts
Time schedules and calendar events
Stock prices and exchange rates

Semantic Web Security

Can I trust a seller on the semantic web. Can I trust a buyer on the semantic web?

To solve, I will need access to more RDF files:

Credit card information
Bank information
Semantic records
Social Security information

Source	Person ID	Person Name	Status
Citybank	11223344	John Smith	trustworthy
VISA	11223344	John Smith	trustworthy
Recorded	11223344	John Smith	unknown
US Social Security	11223344	John Smith	born 10-10-1962

By using RDF files like this, my "Semantic Web Agent" can determine if I can trust the person I am dealing with.

(the "Recorded" information could be supplied by Internet trading companies like eBay, Amazon or the like)

Payment

To serve the semantic web, payment methods have to be developed.

Internet accessible "Deposit Accounts" could be a solution to this.

A deposit account is an account that can only receive deposits. It could be made accessible for everyone on the Internet, and everyone could deposit money to your account only knowing your ID (or your email address, much like PayPal).

Using this payment method everyone could publish their bank account number over the Internet and sell their car without any middleman.

OWL - Your Web Thesaurus

Scenario:

You want to sell a book
You open your OWL agent
You entered “Book” in the category
A new screen is asking you to fill out information about the book
You fill out the ISBN number written on the book
You select "used", and "condition as new", and hit return
Your OWL agent automatically fills out the rest
Author, year, pages, ...... all information is now complete
Your OWL agent has collected all the information you needed to sell the book
You click on Auction

Your Auction Agent

Your Auction agent opens.
You fill out minimum price, and click on "Submit"
You book becomes available to all the auctions on the Internet