Computer communication B

Introduction to the Semantic Web

The semantic web: definitions What is the semantic web?

Nobody knows exactly, because there are broad and varying definitions about it.

Tim-Berners Lee, the inventor of the WWW says (Berners-Lee, Hendlers, J. & Lassila, O., 2001)

“Most of the Web's content today is designed for humans to read, not for computer programs to manipulate meaningfully. Computers can adeptly parse Web pages for layout and routine processing here a header, there a link to another page but in general, computers have no reliable way to process the semantics…. The Semantic Web will bring structure to the meaningful content of Web pages, creating an environment where software agents roaming from page to page can readily carry out sophisticated tasks for users.

The semantic web: definitions

The Semantic Web is not a separate Web but an extension of the current one, in which information is given well-defined meaning, better enabling computers and people to work in cooperation

(Berners-Lee, Hendlers, J. & Lassila, O., 2001)

The semantic web (SW): definitions

“The Semantic Web is a vision: the idea of having data on the Web defined and linked in a way that it can be used by machines not just for display purposes, but for automation, integration and reuse of data across various applications (W3C, 2003)

“Soon it will be possible to access the Web resources by content rather than just by keywords (Anutariya et al, 2001)

Semantic Web: Introduction

The content of the present Word Wide Web is nowadays only accessible and can be elaborated only by people

The Semantic Web is an enlargement of the WWW with semantic information that can be used by computers

With the help of semantic information the content of pages could be processed automatically and computers could make inferences about a search

Semantic Web: Software-agents

Software-agents: are part of software that act in place of the user or in place of another program in relation to an agency (for example the so called “collaborative filtering”) They simulate the qualities and the properties and/or

the preferences of their users They search for extra information on the basis of

which additional decision can be taken They take action independently, and they can

communicate with the user Example: By purchasing something the software-

agent proposes something that is related to it

With the Semantic Web software-agents could execute complicated assignments for which they need relevant informationOrganization meetings or plan tripsSelect specific suppliers to buy a product

The semantic web: characteristics

The semantic web is not different from the www, is actually a developing part of it.

The infrastructures and characteristics should be common Use URI (Uniform resource Identifiers) addressing Use protocols that a have a small and universally

understood set of commands (like HTTP: Hypertext Transfer Protocol)

Be decentralized (like the www) Function on a large scale

The semantic web: The layer cake

The semantic web

Two principles for the construction of the semantic web

1. Downward compatibility. Agents fully aware of a layer should also be able to interpret and use information written at lower levels. For example, agents aware of the semantics of OWL can take full advantage of information written in RDF and RDF Schema.

2. Upward partial understanding. On the other hand, agents fully aware of a layer should take at least partial advantage of information at higher levels. For example, an agent aware only of the RDF and RDF Schema semantics can interpret knowledge written in OWL partly, by disregarding those elements that go beyond RDF and RDF Schema.

Bibliography

The Semantic Web, Scientific American, May 2001, Tim Berners-Lee, James Hendler and Ora Lassila.

http://www.w3.org/ Antoniou, G., Van Harmelen, F. `(2004) “A

Semantic web Primer”

http://www.netlibrary.com/Reader/