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.
The Semantic Web is a web that is able to describe things in a way that computers can understand.
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 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.
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:
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.
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:
Let's call the Internet applications for IBA (I Buy Application), and ISA (I Sell 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.
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, 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.
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.
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.
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:
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:
|Source||Person ID||Person Name||Status|
|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)
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.
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