Abstract
An idea of supporting a user facing a complex and functionally reach system under the assumption that his knowledge about it is incomplete and imprecise and can be expressed (and accumulated) by him using notions not agreed in meaning is presented in the paper. A description logics is proposed that describes the knowledge and constitute a functional basis of an interface of such system. A pilot version of the – built according to the logics – knowledge base and inference engine dedicated to INFOCAST Information System [Dobrowolski et al., 2003] is presented also.