8. A document retrieval system as claimed in claim 7, wherein said relevance value is a value within a range which is equal to or greater than 0 and is equal to or less than 1, and said evaluation value is an arbitrary value within a range which is equal to or greater than 0 and is equal to or less than 1.
7. A document retrieval system as claimed in claim 1 or claim 3, wherein: said evaluation information has an evaluation value which is a value indicated by a real number; and the evaluation value corresponds to the degree of relevance required by the user for each of the documents.