11. The information retrieval method of claim 7 , further comprising displaying the influence of each keyword linearly, and changing the influence of each keyword in accordance with movement of a boundary of each linearly displayed keyword.
11. The information retrieval method of claim 7 , further comprising displaying the influence of each keyword linearly, and changing the influence of each keyword in accordance with movement of a boundary of each linearly displayed keyword. 12. The information retrieval method of claim 11 , wherein the information retrieval method further comprises a pointing device, a boundary of a keyword is displayed as a slide bar on the display device, and the influence is changed by operating the slide bar using the pointing device.