The Semantic Web is about a web of data. The data itself can reside in databases, spreadsheets, Wiki pages, or indeed traditional web pages.

The challenge is to develop tools that can “export” these data into RDF form: RDF plays the role of a common model, as a kind of a “glue” to integrate the data. That does not mean that the data must be physically converted into RDF form and stored in, say, RDF/XML. Instead, automatic procedures, for example SQL to RDF converters for relational databases, GRDDL processors for XHTML files with microformats, RDFa, etc, can produce RDF data on-the-fly as an answer to, eg, queries. RDF data may also be included in the data via other tools (e.g, Adobe’s XMP data that gets automatically added to JPEG images by Photoshop). Authoring tools also exist to develop, eg, ontologies on a high level instead of editing the ontology files directly. Of course, direct editing of RDF data is sometimes necessary, but it can be expected to become less and less prevalent as smarter editors come to the fore.

RDF is nothin gmore as a dream. Some people ike to dream others see that RDF give nothing more llike first step of unification. Try to explore more to see that the expressive power of RDF is huge but at the same time it is also very ambiguous and therefor cannot be treated as good alternative for data representation.

RDF is just a way to represent data. In the Semantic Web RDF is accepted standard to represent the underlying data.

Some see that RDF can be used not just in the Semantic Web, but also to interlink data from different sources as RDF data should be globally unique.

RDF is a standard model for data interchange on the Web. RDF has features that facilitate data merging even if the underlying schemas differ, and it specifically supports the evolution of schemas over time without requiring all the data consumers to be changed.

RDF extends the linking structure of the Web to use URIs to name the relationship between things as well as the two ends of the link (this is usually referred to as a “triple”). Using this simple model, it allows structured and semi-structured data to be mixed, exposed, and shared across different applications.

This linking structure forms a directed, labeled graph, where the edges represent the named link between two resources, represented by the graph nodes. This graph view is the easiest possible mental model for RDF and is often used in easy-to-understand visual explanations.

RDF is a flexible language that allows you to represent data with more expressiveness power