Saturday, September 19, 2009

Semantic Web Tutorial

Semantic Web Tutorial


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.

Semantic Web Example


The Semantic Web. An example application.


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)

Top of Form


Bottom of Form

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)

Top of Form


Bottom of Form

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.

Please go to the next chapter to read more about some semantic web issues.

Semantic Web Issue

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


Person ID

Person Name




John Smith




John Smith




John Smith


US Social Security


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)



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


  • 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

You can read more about OWL in our RDF tutorial.


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

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