New challenges: Group decision systems by means of entropy defined through qualitative reasoning structures

This paper introduces the concept of entropy on orders of magnitude qualitative spaces and, consequently, the opportunity to measure the gain or loss of information when working with qualitative descriptions. The results obtained are significant in terms of situations which arise naturally in many real applications when dealing with different levels of precision. The entropy allows measuring the consensus of expert opinion by use of a distance, and building amethod that enables ambiguous values to be included in analysis and summarizing information.