Let's start with a definition of Semantics. Semantics is closely related to syntax. The syntax is how we say something and the semantics is the meaning behind what we say. Take a sentence in English as an example. The sentence is made up of punctuation, spelling, and the letters. The semantics is what the sentence means.
When we talk about syntax and semantics we are talking about communication. The Internet gave a way for computers to communicate with one another. It gave them a voice so that they could talk to one another. However, just as a parrot can mimic human speech, a computer on the web can only mimic human information. It does not understand what the information means.
The web is made up of web pages that use a syntax that tells how to display or present documents or information for us. The need for the semantic web is because computers and the web were not designed to understand the meaning of what is contained on a web page. Computers can recognize the syntax of web pages, i.e. how to display the information on a web page but not the semantics of what is contained on a web page.
The semantic web is about things, people, events, places and any concept you can think about. The semantic web is not only about understanding the meaning of what is contained on a web page but how these things are related to one another. Two technologies for embedding semantic information in web pages are microformats and RDFa. So, this is not about something that will happen in the future, it is about technologies that exist now... and are happening now.
Once a computer and the web can understand what a person, a place and an event is, it can start helping you interact with these things. A good example is in semantic web searches. Search engines would be more accurate. You could tell the search engines whether you are searching for a person, a place or a song. They wouldn't only depend on keywords but also the semantics contained within web pages. It is about helping computers get us what we want.
See http://microformats.org/about and http://rdfa.info/about by the web consortium.
Post by Bruce Whealton
http://futurewavedesigns.com
http://brucewhealton.com
