Abstract: Two kinds of phenomenon often in data transference:some data elements are lost and some unknown data elements enter into original data. The data was changed into abnormal data due to such phenomena. By using a new mathematical model, theoretical research and application respect to two phenomena were given. This new model is called P-sets(packet sets). P-sets is a set pair which is composed by internal P-set XF(internal packet set XF) and outer P-set XF (outer packet set XF);or(XF，XF ) is called P-sets. In this paper, the concepts and characteristics of F-dependence and F-dependence were presented. I}he dependence theorem and the application of abnormal data separation were given. Data dependence is one of application characteristics and it is a new theory and method in dealing with dynamic data system.

Key words: P-sets, Data dependence, Dependence measure, Abnormal data, Data separation, Application