Anyone worked on Question Answering system?

Hi, Has anyone worked on any "Question Answering System" such as AskJeeves.com or TeRespondo.com (spanish)? Basically what these sites do is try to match your question to a question which is already in their database. The system must however, take insto consideration what the person is looking for, for example: When you search for: "How do I make a chocolate cake?" the software needs to know that you are looking under food [cake = food] then it needs to know that you want to make it, so [make = recipe], and then it can finally get you the aprozximate question (assuming it had this in it's database) "Where can I find the recipe for a Chocolate Cake?". I think this would be the most logic way.... I understand that these methods will require thousands of questions in a database, to make it of any use, but we are prepared to have people for this... Any help would be greatly appreciated... Cheers, Roy