I have a custom blog and news in one website. Each article or post is tagged under several tags.

Now I want to use these tags to build a search system but with some intelligency. I'd like to use a thesaurus, to indicate for example that dollars is the preferred term instead of dollar, and car is the preferred term instead of automobile, that dollar is under money tag, etc. (relations among tags).

What do you suggest for the database structure? I'm trying to find samples of how to implement a thesaurus with no luck.

Many thanks