Voyager questions are an open-ended exploratory question. Deep thought questions are more focused open-ended question with a specific goal that may have multiple answers. Joe Friday questions are very specific questions that have a simple answer. Voyager and Deep thought questions need input from multiple documents, whereas Joe Friday questions require facts, which will probably come from one document.
2. How does a clearinghouse differ from a subject tree?
A clearing house is a collection of Web pages and online documents about a topic. A subject tree is a heirarchy that is organized by topics, and each topic has an associated list of web sites and online documents.
3. How does a meta search engine differ from a general search engine?
A general search engine has an index of a large collection of Web pages by keywords. A Meta search engine allows you to access multiple search engines at once.