Abstract: The paper continues the theme of [ knowledge.ps ]. We differentiate between our approach to knowledge representation and that of others by expressing the following Working Hypothesis: Knowledge is a data type, and knowledge revision is accomplished by continuous operations on it, which are coordinated with its effective basis. Staying in the limits of Belnap's paradigm of the admittance of contradictory information into the computer's memory, our purpose in this paper is to reduce as much as possible all the computable processes needed for modifing the current state of the computer's knowledge and describe conditions for possible maneuvering. In particular, we solve some problems of decidability concerning operations on the minimal states, which are regarded as natural knowledge transformers. We show, also, how to express those operations in lattice theory terms that leads to the simplification of their computation on the lattice of minimal states. The problem of backtracking in the presented context is considered as well.