Context aware adaptive system need to have some model for their adaptive behavior. These models need to have effective adaptive mechanism to react to the changes in the environment. Specifying the adaptive behavior and ensuring the correctness of the adaptive behavior is the challenging task. Correctness of the adaptive behavior can be assured by designing the complete and consistent adaptive rules. While designing the adaptive rule, sometimes there may be situation where some environmental changes are not addressed. In this proposed work we generated the adaptive rules for all combinations of context values in the defined adaptive rules. We have discussed the priority based rule matching process for finding the decision classes for the newly generated rule. We have used Attribute effectiveness, Attribute Autonomy and Minimum value dependency criteria of RBDT-1 method for assigning priority to the attribute. This proposed method creates the new adaptation rules from the existing rule set for the undefined context situation which is influenced more than one context variable. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.