This infrastructure enables metadata interoperability through the design of mechanisms that support common conventions of semantics, syntax, and structure. RDF does not specify semantics for each resource description community, but rather provides the ability for these communities to define metadata elements as needed. RDF uses XML (eXtensible Markup Language) as a common syntax for the exchange and processing of metadata. The XML syntax is a subset of the international text processing standard SGML (Standard Generalized Markup Language) specifically intended for use on the Web.

The XML syntax provides vendor independence, user extensibility, validation, human readability, and the ability to represent complex structures. By exploiting the features of XML, RDF imposes structure that provides for the unambiguous expression of semantics and, as such, enables consistent encoding, exchange, and machine-processing of standardized metadata.

RDF supports the use of conventions that will facilitate modular interoperability among separate metadata element sets. These conventions include standard mechanisms for representing semantics that are grounded in a simple, yet powerful, data model discussed below. RDF additionally provides a means for publishing both human-readable and machine-processable vocabularies.

A Uniform Resource Locator (URL) is a URI that, in addition to identifying a resource, provides a means of acting upon or obtaining a representation of that resource by describing its primary access mechanism or network location. For example, the URL http://www.doodhpatti.com is an URI that identifies a resource (DoodhPatti.com’s home page) and implies that a representation of that resource (such as the home page’s current HTML code, as encoded characters) is obtainable through HTTP from a network host named www.doodhpatti.com.

A Uniform Resource Name (URN) is a URI that identifies a resource by name in a particular namespace. You can use a URN to talk about a resource without implying its location or how to dereference it.

Based on the metadata, intelligent applications such as semantic portals can be created. Metadata creation includes two major parts. First, the ‘Ontologies’ and vocabularies used as the basis in metadata descriptions are defined. Second, the web resources are annotated with metadata conforming to the definitions.

A crucial question for the breakthrough of the Semantic Web approach is how easily the needed metadata can be created. Annotating data by hand is laborious and resource-consuming and usually economically infeasible with larger datasets. Automation of the annotation process is therefore needed.

Semantic Web has generally but not finally five basic building blocks:

• URIs: A global naming scheme
• RDF: A standard syntax for describing data
• RDF Schema: A standard means of describing the properties of that data.
• OWL: A standard means of describing relationships between data items (ontologies defined with the OWL Web Ontology Language)

We are not going to cover these all in detail here however below is a little explanation of URI and RDF (Resource Description Framework).

Why we need a new technology?

Data is present everywhere on web. That is generally hidden in HTML files and is often useful in some situations, but not in others. The problem with the majority of data on the Web that is in this form at the moment is that it is difficult to use on a large scale, because there is no global system for publishing data in such a way as it can be easily processed by anyone. As an example, the information about weather forecast, local sports events, plane schedules, Major League Football statistics, and TV channel guides… all of this information is presented by numerous sites, but all in HTML. The problem with that is, in some contexts, it is difficult to use this data in the ways that one might want to have it in a form. So the Semantic Web can be seen as a huge engineering solution… but it is more than that. We will find that as it becomes easier to publish data in a re-purposable form, so more people will want to publish data, and there will be a incidental and effect. We may find that a large number of Semantic Web applications can be used for a variety of different tasks, increasing the modularity of applications on the Web.

The Concept:

The concept of Semantic Web was first thought up by Tim Berners-Lee, the inventor of WWW, URIs, HTTP. And now Semantic Web is under research phase all over the world.

A dedicated team at World Wide Web consortium is working on SW to improve, extend and standardize the system and many languages, publications, tools and so many other things have been developed. However, Semantic Web technologies are still very much in their infancies, and although the future of the project in general appears to be bright, there seems to be little consensus about the likely direction and characteristics of the early Semantic Web.

What makes Semantic Web?

The Semantic Web is generally built on syntaxes which use URIs to represent data, usually in triples based structures: i.e. many triples of URI data that can be held in databases, or interchanged on the world Wide Web using a set of particular syntaxes developed especially for the task. These syntaxes are called “Resource Description Framework” syntaxes. Read in detail about Pillars of Semantic Web.

URI – Uniform Resource Identifier

A URI is simply a Web identifier, like the strings starting with http or ftp that you often see on the World Wide Web. Anyone can create a URI, and the ownership of URIs is clearly delegated, so they form an ideal base technology on top of which to build a global Web. In fact, the World Wide Web is such a thing: anything that has a URI is considered to be “on the Web.” Every data object and every data schema/model in the Semantic Web must have a unique URI. – Read more about URI in detail.

RDF – Resource Description Framework:

The Resource Description Framework (RDF), developed under the sponsorship of the World Wide Web Consortium (W3C), is an infrastructure that enables the encoding, exchange, and reuse of structured metadata.

This infrastructure enables metadata interoperability through the design of mechanisms that support common conventions of semantics, syntax, and structure. RDF does not specify semantics for each resource description community, but rather provides the ability for these communities to define metadata elements as needed.  Read more detail for RDF.

Future of Semantic Web:

Once the Semantic Web exists, it can provide the ability to tag all content on the Web, describe what each piece of information is about and give semantic meaning to the content item. Thus, search engines become more effective than they are now, and users can find the precise information they are hunting. Organizations that provide various services can tag those services with meaning; using Web-based software agents, you can dynamically find these services on the fly and use them to your benefit or in collaboration with other services.

Though a lot more work has to be done under the umbrella of Semantic Web Technology, Researchers from all over the world are striving hard to bring it in a shape. Till now its implementation into practical world is so rare, but few big companies have started implementing it on trial bases. We can hope for its real execution within few years.

Surface web is also know as appreant web or that pages whos data is clearly readable by just one click. SE Bots read these page very easily.

There are also some pages which are linked up with javascript URLs are not very much visible to Search Engines, URLs such as javascript:__doPostBack(’ctl00$exampledomain$action001′,”); – Read in detail these SEO Enemy URLs.