29-11-2012, 12:59 PM
SEMANTIC WEB
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ABSTRACT
The Semantic Web is an evolving development of the World Wide Web in which the meaning (semantics) of information and services on the web is defined, making it possible for the web to "understand" and satisfy the requests of people and machines to use the web content. At its core, the semantic web comprises a set of design principle. collaborative working groups, and a variety of enabling technologies.
Some elements of the semantic web are expressed as prospective future possibilities that are yet to be implemented or realized.Other elements of the semantic web are expressed in formal specifications.Some of these include Resource Description Framework (RDF), a variety of data interchange formats (e.g. RDF/XML, N3, Turtle, N-Triples), and notations such as RDF Schema (RDFS) and the Web Ontology Language (OWL), all of which are intended to provide a formal description of concepts, terms, and relationships within a given knowledge .
INTRODUCTION
Currently the focus of a W3C working group, the Semantic Web vision was conceived by Tim Berners-Lee, the inventor of the World Wide Web. The World Wide Web changed the way we communicate, the way we do business, the way we seek information and entertainment – the very way most of us live our daily lives. Calling it the next step in Web evolution, Berners-Lee defines the Semantic Web as “a web of data that can be processed directly and indirectly by machines.”
In the Semantic Web data itself becomes part of the Web and is able to be processed independently of application, platform, or domain. This is in contrast to the World Wide Web as we know it today, which contains virtually boundless information in the form of documents. We can use computers to search for these documents, but they still have to be read and interpreted by humans before any useful information can be extrapolated. Computers can present you with information but can’t understand what the information is well enough to display the data that is most relevant in a given circumstance. The Semantic Web, on the other hand, is about having data as well as documents on the Web so that machines can process, transform, assemble, and even act on the data in useful ways.
Imagine this scenario. You’re a software consultant and have just received a new project. You’re to create a series of SOAP-based Web services for one of your biggest clients. First, you need to learn a bit about SOAP, so you search for the term using your favorite search engine. Unfortunately, the results you’re presented with are hardly helpful. There are listings for dish detergents, facial soaps, and even soap operas mixed into the results. Only after sifting through multiple listings and reading through the linked pages are you able to find information about the W3C’s SOAP specifications.
HISTORY
Web 1.0:
Web 1.0 (1991-2003) is a retronym which refers to the state of the World Wide Web, and any website design style used before the advent of the Web 2.0 phenomenon. Web 1.0 began with the release of the WWW to the public in 1991, and is the general term that has been created to describe the Web before the "bursting of the Dot-com bubble" in 2001, which is seen by many as a turning point for the internet.
Web 2.0 Characteristics:
Web 2.0 websites allow users to do more than just retrieve information. They can build on the interactive facilities of "Web 1.0" to provide "Network as platform" computing, allowing users to run software-applications entirely through a browser. Users can own the data on a Web 2.0 site and exercise control over that data .These sites may have an "Architecture of participation" that encourages users to add value to the application as they use it.
The concept of Web-as-participation-platform captures many of these characteristics. Bart Decrem, a founder and former CEO of Flock, calls Web 2.0 the "participatory Web and regards the Web-as-information-source as Web 1.0.
The impossibility of excluding group-members who don’t contribute to the provision of goods from sharing profits gives rise to the possibility that rational members will prefer to withhold their contribution of effort and free-ride on the contribution of others.] This requires what is sometimes called Radical Trust by the management of the website. According to Best the characteristics of Web 2.0 are: rich user experience, user participation, dynamic content, metadata, web standards and scalability. Further characteristics, such as openness, freedom] and collective intelligence] by way of user participation, can also be viewed as essential attributes of Web 2.0.
Architecture Description:
The basic architecture of semantic web contains Identifiers (Uniform Resource Identifiers) and character code as Unicode. Above this layer is the Syntax layer, defining the syntactical realtionship and the base here is XML. Above this layer is the Data Interchange layer with RDF defining the same. Above it the query handling part is handled by SPARQL and the taxonomies is determined by RDFS. The Ontologies are governed by OWL and rules by RIF/SWRL. Above it is the unifying logic and the proof layer. All the aforementioned layers were encrypted using Cryptology. Above these is the Trust layer.
A brief description of all the aforementioned layers and components shall be given in the upcoming segments of the report.
Key Components
Semantic Web has five main components which help in accomplishing the required task and define the functioning of the web:
Uniform Resource Identifier:
A URI is simply a Web identifier: like the strings starting with "http:" or "ftp:" that you often find on the World Wide Web. Anyone can create a URI, and the ownership of them is clearly delegated, so they form an ideal base technology with which to build a global Web on top of. In fact, the World Wide Web is such a thing: anything that has a URI is considered to be "on the Web".
OWL:
The Web Ontology Language (OWL) is a family of knowledge representation languages for authoring ontologies endorsed by the World Wide Web Consortium. They are characterised by formal semantics and RDF/XML-based serializations for the Semantic Web. OWL has attracted both academic, medical and commercial interest.
In October 2007, a new W3C working group was started to extend OWL with several new features as proposed in the OWL 1.1 member submission. This new version, called OWL 2, soon found its way into semantic editors such as Protégé and semantic reasoners such as Pellet, RacerPro and FaCT++. W3C announced the new version on 27 October 2009.
The OWL family contains many species, serializations, syntaxes and specifications with similar names. This may be confusing unless a consistent approach is adopted. OWL and OWL2 will be used to refer to the 2004 and 2009 specifications, respectively. Full species names will be used, including specification version (for example, OWL2 EL). When referring more generally, OWL Family will be used.