What is the "Semantic Web"? It's nothing.
No one knows how to define it other than just listing about every current web-related technology being developed. It's at best a catch-all for the current technology, and at worst a meaningless term that a bunch of charlatans use to convince someone to give them money, or to convince others they are "technically hip".
Some day in the future, something being developed today will be useful, then someone with great hind-sight will say "Yes, that is what I meant by the Semantic Web!"
Keep in mind, you cannot encode semantics in any computer representation. Anyone whose says you can is kidding you and/or themselves. It's all just syntax, since semantics are something no one really understands other than some concept people seem to agree on.
If I say "car", you know what I mean and I know what I mean. Since we likely agree, or can find no evidence that we are not referring to the same concept, the three characters can be said to have semantic meaning, but they do not really. It is you and I that give those characters semantics, not the computer. Most work on semantics and ontologies just create more elaborate syntax, which generally just obfuscates things so people think its semantics, and even probably convince themselves it is.