A Boolean search for "winter AND Yosemite AND camping" would only retrieve documents which contained all three words "winter," "Yosemite," and "camping" since the AND operator requires that a term be present. The OR operator allows one of the terms to be present, and the NOT operator rejects documents if a term is present. A more complex search, "winter AND (Yosemite OR Yellowstone) AND skiing NOT downhill" would retrieve all documents which referred to skiing in either Yosemite or Yellowstone in winter, unless there was a specific reference to downhill. Of course, the documents would have to match the search terms exactly, so a document discussing skiing in Yosemite in January would not be retrieved unless it specifically mentioned the word winter.