An Incremental Updating Method for Computing Approximations by Matrix While the Universe Evolves over Time

Most of the methods for calculation of the upper and lower approximations of a concept are presently based on static information systems. In fact, the information system usually evolves over time, including the change of its universe, attribute set and values of attributes. In this paper, from the point of view of matrix, an incremental updating method is proposed for updating β-approximations under variable precision rough sets while the universe of information system evolves with time. Furthermore, the theorems on updating the approximations of a concept by the tool of matrix are given. The process of calculation on this updating method is presented. Finally, a numeric example is given to illustrate the correctness of the proposed incremental updating method based on the matrix point of view.