However, the major weakness of relevance feedback
method [1, 3, 5] is that the user has to judge whether the
retrieved documents are relevant or not. This may not be
appropriate for users who want to retrieve information
immediately. One way to address this disadvantage is via
relevance feedback based on the retrieval system [5], a
method hat assumes the upper ranked n document are all
relevant and includes those documents in the relevance
feedback process. However, this method depends strongly on
the retrieval effectiveness of the results of initial retrieval.
The retrieval effectiveness of the retrieval system was
lowered significantly when the retrieved documents among
the upper ranked n documents did not satisfy the user’s
information needs.